[coreboot] useful hardware - dip8 to soic8 adapter
peter at stuge.se
Sat Jun 20 01:32:12 CEST 2009
Urja Rannikko wrote:
> All one would really need is some fast µC (enough fast to keep up
> with mb SPI and convert the command set) with two SPI interfaces to
> convert SD/MMC to motherboard SPI. That would be really cool btw,
> if it would work :)
Basically, it won't.
The protocol used on the mainboard has pretty strict timing for
response from the flash chip, no microcontroller will be able to keep
up. It is even doubtful if a state machine in programmable logic
would be able to respond quickly enough.
Note that only MMC (the very old cards) use 1-bit SPI. Any newer card
uses a wider interface, which means even more complex translation
And even if the translation state machine would be fast enough, if
e.g. it runs off it's own clock at maybe 100MHz instead of whatever
is on SPI, the consumer grade flash memory cards can themselves have
longer response times than what is allowed by the mainboard SPI.
MMC has unlimited response times, as an example. Ie. the card can
take as long as it wants to respond, at least for writes.
The cards can also have rather complex voltage requirements.
All in all, a ton of work, and even doubtful that it could succeed.
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