The BIOS on the motherboard will always perform a power-on-self-test “POST” during power up, usually this test is perform to ensure proper system function and if a failure occurs – the “POST” will identify the failure and emits a beeping sound to prompt the service technician to take corrective action ASAP.
The exact meaning of the beeping codes varies from different BIOS developers, there are 3 basic BIOS developer today, the most popular BIOS is made by “American Mega-trend” - AMI, Award and Phoenix BIOS. The beep codes for this AMI & Award BIOS developer are provided in this memory troubleshooter guide, we do not provide beep code reference for Phoenix BIOS and custom BIOS written by other companies other than the two mention.
Beep codes are not entirely consistent sometimes to detect the exact failures, but generally it is still the most dependent methods to diagnose a fault without opening up the PC system or using any diagnostic software.
Award is the another popular BIOS developer and they use the fewest beep codes by far.
Procedures – The normal procedure is to power up the PC system, watch for error message on the monitor screen and listen to the PC beep tone. A single beep during boot-up process is normal and does not indicate a failure if the system continues to boot-up.
1 Long Beep tone - Memory Problem
1 Long Beep and 2 Short Beeps - DRAM Parity failure
1 Long Beep and 3 Short Beeps - Video error
Continous Beep tone - Memory or Video memory failures
Well, this is tricky situation. Typically you may want to begin by finding out if it's a memory related problem. DocMemory PC Memory Diagnostic software is designed for this very purpose. You can start by downloading a copy of the sofware from DocMemory Diagnostic Site , follow the setup instructions and run a diagnostic test on your PC memory.
If all Memory tests results returns good, you will need to isolate and examine other possiblities such as CPU, Motherboard or other peripherals that you have in your PC.
One of the most common memory problem faced in older PC system during boot-up is “incorrect memory sizing” or the error number 164. Sometimes failures could be caused by incorrect software setting, sometimes it could be caused by hardware – which could be easily fixed if you know where the faults lies.
In most cases hardware failures are caused by the natural aging process of the memory components, defective memory module socket, dirty contacts, cold solder joints during assembly and memory module not seated properly in the socket due to vibration.
It is important to pay attention to intermittent memory failure, before you make any expensive decision to replace the expensive memory - try cleaning the memory module contacts for both old and new ram to see if the problem can be fix:
Here ‘s the How to :
– Contact Clean (Purchase from local computer hardware store)
- Cotton Bud ( For cleaning contact with)
- Screwdriver (pc case removal)
- PC user manual
1 - ensure environment is static safe by removing any unwanted plastic, bags from your workbench. Keep the computer system plugged into your AC unit but ensure that the power switch on the PC is turned off. Keeping the PC plugged in the AC will ensure that case is grounded thus reducing the possibility of damaging the module or system from ESD (Electro Static Discharge)
2 -After removing the casing cover, ground yourself by touching any of the metal surfaces on your computer casing. Doing this step discharges any static built up on your body and clothing
3 - Visually locate the computer memory expansion slots. This is normal visible but if in doubt, refer to your operation manual instruction book.
4 – the first thing to do is to remove the memory module and perform some visual inspection to check the memory socket which sits the memory module. Make sure all the pins are straight, no cracks or broken pins must be found.
A Wet the end of a cotton swab with the solvent, the swab should be wet but not dripping
B Using a circular motion, clean the contacts on the memory module.
C Allow the contact surface to dry thoroughly.
D Replace the memory module into the socket.
E Repeat steps B through D for each module you have.
F Power on the computer to test the RAM.
G If you see no memory errors, replace the PC's case and power-up away.
5. While contact cleaner is preferred, it is also a well-known trick that you can also clean contacts with a pencil eraser.
6. Continuing RAM errors are usually a sign of a bad memory module. If cleaning the contacts doesn't solve your problem, try to isolate the faulty module and replace it.
Removing the modules one by one from motherboard
This is simplest method for isolating a failing module, but this may apply only if the motherboard have more than one module on the SIMM or DIMM Slot. By selectively removing module one at a time from the system and then running the test you will be able to find the bad module very quickly. Be sure to mark the module that passes or when it test fails.
Swap the modules around
When none of the modules can be removed, swap and rotate modules to find which module is defective. This technique can only be used if there are two or more modules in the system. Change the location of two modules one at a time.
For instances, place the module from SIMM slot 1 into slot 2 and place the other module from slot 2 in slot 1.
Run the diagnostic test and if either the failing data bit or address changes, you know that one of the module you have just swap is defective. By using several combinations of module swapping you should be able to check which module is defective.
Replacing with known good module
If you are unable to use either of the above two techniques, you are left to use known good modules and selectively replace of modules one by one to pin point the memory failure. This is the easiest way to detect memory failure.
Removing and cleaning the metal contacts
If your PC system is older, sometimes dust and oxidation will cause poor contact in the SIMM/DIMM slot. Remove the module and clean the gold or tin contact with a “pencil eraser” or any cleaning solution used for video and audio head cleaning. Make sure you remember which slot is being used, and be careful not to reverse the module while reinserting into the SIMM/DIMM slot
Identifying memory failure using motherboard BIOS codes
If you are not trained to perform the correct diagnostic methods – majority BIOS developers and motherboard manufacturers have device a simple way of telling you if your system is having problem by emitting beeping tones from the build in speaker on the motherboard, without the aid of a memory tester.
This section is written with the assumption there is a general understanding of PC operating system, in order for you to be capable of performing the diagnostic procedures detailed below.
We will try to describe the entire process in full detail, however it is beyond the scope of this troubleshooter guide to provide all the necessary information to cover all possible PC system failures. For further assistance with non-memory related failures, please consult your PC manual or manufacturer support help online system. If your particular question is not addressed in this section – please send us an e-mail and we will do our best to provide you with the right answers.
When you are experiencing memory failures on your PC system, there are several faults to determined, check the following:
* PC system does not boot-up
* HIMEM.SYS does not load
* Memory failure due to system hanging up, or system rebooting after running a large program.
* Fail to install win3.1, Win95 and Win98
* Windows program is unstable
* Continous beeping sound emitted by system during power up
* Continous ram count during boot-up , without loading Windows program
* No display other than blue screen on the monitor during boot-up
* Totally no video display on the monitor.
* System hang or rebooting after prolong usage.
All of the above are typical of memory related failures, you need to be either well trained or PC knowledgeable to be able to perform the correct diagnostic methods.
Once a memory failure has been detected, identifying the defective module is not an easy task either. With a large variety of motherboard provided by different manufacturer around the world, and with the many different combination of SIMM/DIMM slots provided, it would be difficult if not impossible to assemble a complete information about how a particular memory error would map to a failing memory module.
However, there are some basic rules that may be taken to pinpoint defective modules using a memory diagnostic software as an aid.
AMI BIOS is the most popular BIOS used by most motherboard manufacturer- you should be able to determine your system BIOS by reading the screen display on the Top screen during power up.
Procedures – The normal procedure is to power up the PC system, watch for error message on the monitor screen and listen to the PC beep tone. A single beep during boot-up process is normal and does not indicate a failure if the system continues to boot-up.
1 Beep tone - DRAM refresh failure
2 Beep tone - DRAM Parity failure
3 Beep tone - Base 64K RAM failure
4 Beep tone - System timer error
5 Beep tone - CPU failure
6 Beep tone - Keyboard controller error
7 Beep tone - Virtual mode error
8 Beep tone - Display memory read/write error
9 Beep tone - ROM BIOS checksum error
10 Beep tone - CMOS register read/write error
11 Beep tone - Cache memory error
Continous Beep tone - Memory or Video memory failures
72 bit memory is commonly known as ECC memory. It has an additional 8 bits for Error Correction Check 64 bit memory is non-ECC. 72 bit or 64 bit configuration are typically found in 168 pin DIMMs
36 bit memory is commonly known as parity memory. It has an additional 4 bits for parity checking. 32 bit memory is non-parity. 32 bit or 36 bit configuration are typically found in 72pin or 30 pin SIMMs
Well the truth is :
The SDRAM has multiple internal banks. The 16M SDRAM has 2 banks, the 64M has 4 banks. When you tell the SDRAM a ROW or COLUMN address you must also specify which BANK you are referring to. The way to do this is by the 'bank address' (BA). Herein lies the problem.
For some unknown reasons, suppliers have lumped together the ROW address pins with the BANK address pins and simply refer to them as 'address' pins. For the 2Mx8 SDRAM some suppliers claim to have 11 ROW address plus 1 BA, other just say 12 addresses. That's just addressing, for refresh requires you also specify the refresh interval (tREF). For a distributed refresh scheme you simply divide tREF by the number of refresh cycles to get the auto-refresh interval. In both cases for the SDRAM it works out like:
The upshot is that for distributed refresh schemes these two devices are identical in both addressing and refresh. (For a burst refresh scheme, the 32ms tREF is a subset of the 64ms.)
For the general PC application the 2K device works fine. The 4K device offers no advantage. Note that this is not the case for asynchronous DRAM where there truly is a difference in addressing between 2K and 4K.
High density DIMMs have lots of chips on them and therefore possess a higher capacitive load on the address and control signals in comparison to lower density DIMMs. Some designers use re-drive buffers on the DIMM to boost the signals to reduce system loading when compared to the same high density module without buffers. But,
the buffers introduce a small delay into the electrical signal, so adding buffers to a standard density module would have the effect of slowing down the signal, compared to the same low density module without buffers.
CL stands for CAS Latency. It is a programmable register in the SDRAM that sets the number of clock cycles between the issuance of the READ command and when the data comes out. Smaller number for CL indicates faster SDRAM within the same frequency.
SDRAM, EDO and FPM chips look similar to each other. The best way to tell the difference is to reference the part number on the chip. Most DRAM manufacturers have reference books or lists on their web sites. By looking at a memory module one can attempt to guess what it is. A general guideline is to look at the IC type and size. The EDO and FPM chips are typically packaged in SOJ form and are thicker when compared to that of the SDRAM chips which are typically packaged in slim-line TSOP form. The EDO/FPM chips typically have a marking of -60 at the end of the string of numbers and that of the SDRAM chips typically have markings of -12 -10 -8 -7.5. A SDRAM module typically has a row of the resistor or resistor arrays above the contact tabs.
A memory module is made up of electrical cells. The refresh process recharges these cells, which are arranged on the chips in rows. The refresh cycle refers to the number of rows that must be refreshed.
The common refresh cycles are 2K, 4K and 8K. Refresh cycle together with refresh period determines how often refresh is needed, which is defined as Refresh Rate.
For the same refresh period, 4K refresh parts needs to be refreshed more frequently than 2K parts. For the same size DRAM, 4K refresh part consume less power than 2K refresh parts.
Some specially design DRAMs feature self refresh technology, which enables the components to refresh on their own -- independent from the CPU or external refresh circuits.
Self refresh, which is built into the DRAM itself, reduces power consumption, and it is commonly used in notebook computers
EDO DRAM speeds up memory transactions by as little as 5% or by as much as 25% over conventional DRAM, depending upon how much Cache you have on your motherboard. Less Cache on the motherboard will result in a larger speed increase when adding EDO DRAM. EDO eliminates a wait state between the execution of sequential-read commands from memory, giving the CPU significantly faster access to memory.
It means you may experience system errors in a 100mhz system because the memory's performance cannot keep up with the system requirement. The system will operate at the speed of the slowest component. For example, installing 66MHz SDRAM memory in a PC-100 system will cause the bus to operate at 66MHz, rather than the speed it was designed to operate at.
A PC100 or PC133 compliant memory includes a label affixed to it which identifies the module as "PC100 compliant" or "PC133 compliant" . An attempt can be made to verify it by looking at the chip marking which should indicate "-8" or "-7.5" after the string of manufacturer part number, though this may not be entirely accurate.
The early SDRAM DIMM design has 2 clock inputs to drive all the SDRAM chip. This was found to be insufficient due to loading on these inputs. Some 4 clock modules will not work in systems that are designed for 2 clock, but some will. SOME 2 clock modules might not work in systems designed for 4 clocks, but then again some will.
4 clock modules are the current standard and it is unlikely to change again.
PC SDRAM is a loose general term for SDRAM that runs at 66 MHz and has an SPD chip for compatibility with P-II motherboards.
PC100 SDRAM refers to PC100 SDRAM chips or DIMMs that meet INTEL PC100 qualification standard. These parts are designed to run at 100 Mhz front side bus (FSB) speeds.
Registered SDRAM - This is SDRAM module with Register for Address and Control Signals. Registered DIMMs reduce the loading of DIMM to the motherboard so that larger capacity DIMM modules and more DIMMs can be populated on a motherboard.
It is a technique used widely on servers to increae the amount of memory the system can support. The Registered DIMM is a little slower in access timing versus that of the unbuffered counterpart.
This section provides a general guideline on memory upgrades based on your computer systems CPU. This is intended as a broad guideline. Please consult your system user manual for further details of your system requirement
Yes, only if you have a 100 MHz system bus. No,if you have a 66 MHz system bus. On certain system, a non-PC100 module may be "pushed" to run in a 100 MHz system, but the results are not guaranteed and may lead to system instability.
It's easy to find out how much memory your PC has :
1. From your User/Owner's Manual
Consult your user/owner's manual for details about the original memory configuration and capacity. If you've misplaced the manual, you may be able to contact the retailer where you bought the PC from.
2. If you have a hand-me-down PC or inherited a pre-owned PC, you probably may not have the user manual or know any detail of the original memory configuration or the memory configuration may have been changed. Then you may want to try one of the following options:
2a) Ask Your PC
If your PC is running Windows NT/98/95, use the right mouse-click on "My Computer" then select "Properties." The total memory is calculated and displayed under the Tab that shows "General" in the system property dialog box.
If your PC is running Windows v 3.1 or older, go to the DOS prompt and type in "MSD."
2b) Ask Your Mac
If you're a Mac user, select "About This Macintosh" or ("About This Computer") from the
Apple menu on the upper left corner of your Desktop. This will provide information about
your Mac's total memory (built-in memory plus DIMMs or SIMMs installed).
Determining your needs
The amount of memory you need is determined by several factors; the software,
operating system and the number of programs you want to have open at the same time.
When you determine memory needs, you'll also want to consider what your needs will be
six months down the road. If you think you may be upgrading your operating system or
adding more software, it's a good idea to factor that into the equation now.
The following user profile will also help guide your decision:
Business user (64MB-128MB)
Light to Medium usage: runs 2 or 3 applications at one time. Mainly used for word processing, e-mail, fax and communication, database type of application
Home multimedia user (64MB - 128MB)
Light to Heavy usage: runs 2 or 3 applications at one time. Mainly used for word processing, e-mail, surfing the internet, with Heavy user may include use of database, Graphics & 3D intensive games.
Graphics user (128MB - 512MB)
Light to heavy: runs 3 or more applications at one time. Graphic page layout, illustration/graphics. and Heavy users also need photo editing, font packages, multimedia and presentation software.
CAD Design (256MB - 2GB)
Light to heavy: CAD and CAM software. Heavy users need 3D CAD and solid modeling
These days, when one buy a PC, it's primary intended purpose is for speed and performance especially capable of incredible performance for huge graphic and multimedia application. In order for smooth efficient operation of PC with these new memory hungry softwares, a lot more memory is required. In the past, 8MB or 16 MB or 32MB used to be plenty enough, but with software program increasing in size, 64MB is the least that a Windows based PC would require. Today's PC are being shipped with minimum 64MB and even 128MB installed. If you plan to take advantage of the latest technology developed into new software, you should either choose to upgrade your PC's memory or buy one with at least 64MB or more pre-installed.
Majority of the Pentiums computers have 2 banks of two SIMM sockets on the motherboard, each bank must have a pair of same value and type of memory to be utilized by the system.
Most Pentiums computers uses 72 Pin SIMMs. Installation requires 2 SIMMs per bank to upgrade. (2 sockets per bank)
Typically, Pentiums Computer with frequency of 166MHz and up have SIMM and DIMM sockets on board and use 168 Pin DIMMs and 72 Pin SIMMs on the same motherboard.
Pentium computers utilizing 168 Pin DIMMs require 1 DIMM at a time, (1 socket per bank.)
Memory Types: Generally EDO (extended data out) DRAM in matching pairs. Older Pentium computers (60MHz -100MHz) require FPM (Fast Page Mode DRAM.) Newer 100MHz to 200MHz MMX computers, CYRIX 6X86 and AMD 586 class processors uses EDO or FPM, and in some machines SDRAM (DIMMs.)
More memory will not increase the speed of the CPU, but it will reduce the time a CPU spends waiting for information from a hard drive. Since RAM provides data to a CPU faster than a hard drive, you will not have to wait as long for programs to execute.
- new memory modules
- screwdriver (pc case removal)
- pc user manual or guide
Tips on Memory Module Installatioon
1. ensure environment is static safe by removing any unwanted plastic, bags from your workbench. Keep the computer system plugged into your AC unit but ensure that the power switch on the PC is turned off. Keeping the PC plugged in the AC will ensure that case is grounded thus reducing the possibility of damaging the module or system from ESD (Electro Static Discharge)
2. After removing the casing cover, ground yourself by touching any of the metal surfaces on your computer casing. Doing this step discharges any static built up on your body and clothings
3. Visually locate the computer memory expansion slots. This is normal visible but if in doubt, refer to your operation manual instruction book.
4. Insert memory upgrade according to illustration in guide. Take note of
- modules keyed notches and match to socket
5. Replace case to complete installation.
Note: when restarting your computer, note any error messages that is being displayed and update your configuration setting accordingly.
This is not an error. This is exactly what should happen when installing memory. Your system "sees" the new memory, but your BIOS does not. You must run the CMOS setup utility to allow the BIOS to 'write' the changes in extended memory to the CMOS setup. There are several ways to access your setup, but the normal method is to hit your F1 or F2 key when you first boot up. Some systems require Control+Alt+Esc, while others require the delete key to enter setup. Check your manual for the exact key strokes.
Generally speaking, EDO is for Pentiums 120Mhz and up. Most early Pentiums (60MHz -100MHz) prefer Fast Page Mode (non-EDO) memory. Some earlier Pentiums can use EDO, but it may require replacing the slower standard EDO memory, and changing your BIOS. This is not recommended for most users.
EDO memory will not work in 486 computers. Parity memory, which is actually Fast Page Mode with 4 bits for parity checking, works in all computers. If your system does not use parity, it will ignore it. However, if your system does require parity, then you must use parity modules. Newer Pentium systems can be configured to use either parity or non-parity modules but need to have the BIOS set up accordingly.
EDO memory has a faster read timing than FPM but has the same write timing. FPM is commonly used in 386 and 486 computers, while EDO is for Pentiums only. Apple computers should be configured with Fast Page Mode memory.
Pentium motherboards require the installation of matching pairs when using 32 or 36 bit 72-pin memory. The motherboard is 64 bit and would necessitate the use of two 32 bit or two 36 bit modules to equal the 64 bit mainboard.
Try installing the EDO modules in the bank containing the OEM (original) factory SIMMs and moving the OEM SIMMs to another bank. Many times this will resolve the conflict. If this does not resolve your problem, you may need to exchange the EDO modules for Fast Page Mode (FPM) memory available at your place of purchase. Also remember, EDO memory does not work in 486-based systems.
No. SDRAM or Synchronous DRAM systems utilize 64 bit, 168-pin DIMMs rather than 72-pin SIMMs. Leave your existing memory and install one additional module. (168-pin DIMM) Make sure the memory is SDRAM.
ESD (Electrostatic Discharge) is Static electricity . This energy is found in air surrounding us and can damage electronics components in a computer such as Harddisk drive, Floppy Disk drive , motherboard , CPU, memory modules etc.. ESD occurs when one touch an object that conduct electricity.
To protect your memory module from getting damage by ESD, always keep electronics components in AntiStatic packaging until ready to use.
CL2 parts process data a little quicker than CL3 parts in that you have to wait one less clock cycle for the initial data. However, after the first piece of data is processed, the rest of the data is processed at equal speeds. Latency only affects the initial burst of data.
Once data starts flowing, there is no effect. Bear in mind, a clock cycle for a PC100 module is 10 nanoseconds so you probably won't notice a significant performance difference.
Most systems will accept either latency part. However, there are some systems that require either CL2 or CL3 parts.
Most SDRAM is backward compatible and can run at any bus speed slower than it is rated to run.
For instance, a PC133 SDRAM DIMM is capable of running at 133MHz, 100MHz, and 66MHz. There are some older motherboards that require 66MHz SDRAM and that will not accept PC100 or PC133 SDRAM, but they are the exceptions to the rule.
All PC100 and PC133 SDRAM DIMMs that are manufacturerd by the original manufacturer such as Micron,Samsung,NEC,Toshiba are built on 6 layer Printed Circuit Boards (PCBs), except for modules build by 3rd party manufacturer especially from Taiwan which typically are 4 layers. Physically you will not be able to tell the difference between the 4 or 6 layer just by looking at the PCB board. The best way is to visit the manufacturer website for more information or call their toll free number to find out.
OEM is an acronym for "original equipment manufacturer" and OEM memory means - the memory chips and PCB boards are made by the semiconductor manufacturer themselves -and the same memory that the largest PC manufacturers worldwide such as Dell, Compaq, Apple buy for use as original equipment in their systems.
No. When adding new memory, you need to match what is already in your system. Parity modules have an extra chip that detects if data was correctly read or written by the memory module, depending on the type of error. However, a parity module will not correct the error.
You can determine if your system has parity by simply counting the number of black memory chips on each module.
Parity and ECC memory modules have a chip count divisible by 3.
Different sizes of SDRAM modules can be mixed together. You do not need to fill each memory slot with the same size module, and yes, you should be able to add a 128MB module to the existing open slot on your motherboard.
Rule of thumb, the largest module should always be placed in the first slot for best performance.
Internet browsing speed depends on several factors, including your modem connection speed, traffic on the site you're visiting, and the other components in your system.
You will probably notice the biggest improvement from additional RAM if are viewing or working with large files , such as photos and digital audio and video, or if you switch between your browser and other applications often.
The term "registered" refers to how the memory module processes signals.
Registered modules contain a register that delays all information transferred to the module by one clock cycle.
This type of memory is primarily used in servers and was designed for modules with 32 or more chips on them to help ensure that data is properly handled.
While most PCs will only accept unbuffered SDRAM, there are some that accept registered SDRAM. Keep in mind that when you install registered SDRAM, all of the modules installed in your PC must be registered because unbuffered and registered modules are not interchangeable.
If your PC has a 133MHz front side bus , you will need PC133 SDRAM.
If your PC has a 100MHz FSB, you can use PC100 or PC133 SDRAM. All PCs that accept PC100 SDRAM will also accept PC133 SDRAM; however, your memory will only run as fast as the slowest "link" in your system. If you have a 100MHz FSB or any PC100 modules installed, any PC133 modules that you install will only operate at 100MHz.
PC133 SDRAM doesn't offer any immediate benefit over PC100 SDRAM if you have a 100MHz FSB. However, if you are planning to upgrade to a system with a 133MHz FSB in the future, you may be able to use the PC133 modules you purchase now in your future system.
CAS Latency (also referred to as latency) is the amount of time it takes for your memory to respond to a command.
Specifically, it is the length of time between memory receiving a command to read data, and the first piece of data being output from memory. Latency is measured in terms of clock cycles and is often noted as CL2 (two clock cycles) or CL3 (three clock cycles).
No. PC133 memory is designed for use on systems with a 133MHz front side bus or slower. If your 200MHz front side bus is on a system with an AMD Athlon processor, you probably need PC1600 or PC2100 DDR modules
RAM and virtual memory are two different things. Virtual memory allows you to use a portion of your hard drive as though it were RAM. Because your hard drive is up to 100 times slower than your RAM, virtual memory is much slower than RAM.
When you upgrade your RAM, you may discover that you use your virtual memory less because you will now have more memory available to complete the tasks that were previously handled by your virtual memory.
There are several signs indicating it may be time to upgrade your memory.
If you see your mouse pointer turn into an hour glass for significant periods of time, if you hear your hard drive working, or if your computer seems to work more slowly than you expect, the reason is probably insufficient memory.
When the memory is full, your system transfers data to the hard drive. This is called swapping. Since the hard drive is considerably slower than DRAM memory, your system seems slower altogether
Most motherboards that do not have an ECC function within the BIOS are still able to use a module with ECC, but the module will run in non-ECC mode.
Keep in mind, there are some cases where the motherboard will not accept an ECC module, depending on the BIOS programming. The only sure-fire way to test this is to place the module in the motherboard and see if the BIOS will recognize the memory addition.
The two different types of modules (buffered/unbuffered) are not interchangeable and even use slightly different printed circuit boards (PCBs). If you try to install the wrong type, the first notch on the bottom of the module will be offset.
You can determine if the module is buffered by looking at the leads next to the first notch. If the leads are evenly spaced, the module is buffered. If the leads are not evenly spaced (a larger PCB area next to the lead) the module is unbuffered.
Buffered EDO and FPM DIMMs have a buffer logic chip that is used to distribute the load placed on the chipset and is primarily used only in servers on PC platforms. Apple computers have used primarily buffered modules until their recent G3 and G4 series computers
The general rule of thumb in deciding what type of memory you need is to look at what's already installed in your system.
To find out if you have ECC, parity, or non-parity memory, count the number of chips on the module. Divide the total number of chips by three.
If you can evenly divide the number of chips by three, the module is ECC or parity, if not, then it is a non-parity module.
So what if your system does have ECC or parity memory (the chips are evenly divisible by three), how do you know which one you have? One way is to look at the part numbers on the chips of your module. If each chip has the same part number, you have ECC.
If one chip is different, you have parity.
If you are building a PC and deciding which type to use, the following guidelines should help. If you plan to use your system as a server or a similar mission critical type machine, it is to your advantage to use ECC. If you plan to use your PC for regular home, office, or gaming applications, you are better off with non-parity.
Using ECC decreases your PC's performance by about 2%.
Current technology DRAM is very stable and memory errors are rare, so unless you have a need for ECC, you are better served with non-parity SDRAM.
DDR SDRAM comes in two speeds: PC1600 and PC2100. Despite what these names imply, DDR is twice as fast as PC100, not roughly twenty times faster.
PC100 SDRAM modules have a bandwidth (the amount of data they can move) of 0.8GB/sec. Since DDR SDRAM can move data twice as fast as SDR SDRAM, 200MHz DDR (100MHz doubled) has the bandwidth of 1.6GB/sec, or 1600MB/sec.
Hence, the name PC1600. 266MHz DDR SDRAM (133MHz doubled) has the bandwidth of 2.1GB/sec and is referred to as PC2100.
SPD (serial presence detect) is a small non-volatile RAM chip attached to SDRAM modules that contains information about the memory.
This information includes the number of row addresses, number of column addresses, error detection/correction, refresh rates, data width, and the interface standard.
It also contains less important information such as the module serial number and manufacturer code. When your computer powers up, it sets the row and column settings and the timings for the module based on the information in the SPD.
SPD is required in SDRAM that is 66MHz, PC100 and PC133 compliant. Standards set by Intel and JEDEC ensure that data is entered in appropriate locations so the motherboard BIOS can understand what this data means.
The SPD standard allows greater flexibility for incorporating identification of new features and technologies on memory modules.
DDR and SDRAM can be unbuffered or registered. EDO and FPM can be buffered or unbuffered. Buffered modules contain a buffer to help the chipset cope with the large electrical load required when the system has a lot of memory. Registered modules do not have a buffer but do contain a register that delays all information transferred to the module by one clock cycle. Buffered and registered modules are typically used only in servers and other mission-critical systems where it is extremely important that the data is properly handled.
Some systems require 3.3-volt modules, and others require 5-volt modules. The two are not interchangeable, and the different modules actually have slightly different notches so that you won't accidentally install a 5V part in a 3.3V slot or vice versa.
DIMM stands for dual inline memory module, and SIMM stands for single inline memory module. The gold or tin pins on the lower edge of the front and back of a SIMM are connected, providing a single line of communication paths between the module and the system.
The pins on a DIMM are not connected, providing two lines of communication paths between the module and the system, one in the front and one in the back.
SIMMs and DIMMs are not interchangeable; they are different sizes and they install into different types of sockets.
Extended data out (EDO) memory and synchronous dynamic random access memory (SDRAM) are two different types of memory technology. SDRAM is the newer, faster type of the two. The biggest difference between the two is that SDRAM is synchronized to the CPU clock.
Most systems accept either EDO or SDRAM, but not both.
If you have more than 256MB RAM installed, you will receive a memory failure message when you run Symantec's Norton Diagnostics. The problem is caused by a limitation of the test and does not mean that you have faulty RAM.
According to the Symantec Web site, "Norton Diagnostics cannot run a memory test on systems having more than 256MB of memory. This is a limitation of Norton Diagnostics and it is not a problem with your computer's RAM."
Symantec doesn't currently have a way to fix this problem, so your best course of action is just to ignore any error messages you receive.
You can find Symantec's description of the problem at http://service1.symantec.com/SUPPORT/nunt.nsf/docid/1999090713442709&src
No. When adding new memory, you need to match what is already in your system. ECC (error checking and correcting) modules have an extra chip that detects if the data was correctly read or written by the memory module. If the data wasn't properly written, the extra chip will correct it in many cases (depending on the type of error). Non-ECC (also called non-parity) modules do not have this error-detecting feature.
You can determine if your system has ECC by simply counting the number of black memory chips on each module. ECC (and parity) memory modules have a chip count divisible by 3. Any chip count not divisible by 3 indicates a non-parity memory module.
The answer to this question will vary depending on the type of system you have. In a system with a 32-bit processor (486 for example) 30-pin SIMMs must be installed in groups of four, and a 72-pin SIMM can be installed individually. In Pentium class systems, however, you cannot use 30-pin SIMMs, and 72-pin SIMMs must be installed in pairs. You can use 30-pin and 72-pin SIMMs together if the motherboard has the sockets for them.
Synchronous graphics random access memory (SGRAM) is a type of DRAM that is designed for graphics hardware requiring high-speed throughput for applications such as 3-D rendering and full-motion video. SGRAM is often integrated into your motherboard or graphics card.
EEPROM stands for "electrically erasable, programmable, read-only memory." While data stored in DRAM is lost when the power is turned off, data stored in EEPROM can be retained when the power is turned off. EEPROM can also be erased and reprogrammed.
Though the names look similar, SDRAM and SRAM are really quite different. Static random access memory (SRAM) is usually used for the cache of a system. It is very fast and very expensive, but a relatively small amount is needed to build a cache. Cache memory was designed to improve upon the performance of the processor and the memory subsystem, and is usually located next to the processor.
Most desktops and laptops use dynamic random access memory (DRAM) for the main system memory. Synchronous DRAM (SDRAM) is a particular type of DRAM used by some systems. Other types of DRAM include fast page mode (FPM), extended data out (EDO), and double data rate (DDR or DDR SDRAM).
All SDRAM is backward compatible and can run at any bus speed slower than it is rated to run.
For example, a PC133 SDRAM DIMM is capable of running at 133MHz, 100MHz, and 66MHz. There are a few older motherboards that require 66MHz SDRAM and that will not accept PC100 or PC133 SDRAM, but they are the exceptions to the rule.
Keep in mind that your memory run will only run as fast as the slowest component installed. If you install PC100 memory on a system with a 66MHz front side bus, the memory will only run at 66MHz.