[coreboot] SPD sanity check

[ron minnich]

OK, well, I did not quite get the answers I hoped for. So here go my comments:

On Thu, Oct 1, 2009 at 5:04 PM, ron minnich <rminnich at gmail.com> wrote:

> dimm 50
> 00: bad device: 01
>
>
> dimm 51
> 00: bad device: 01
>
>
> dimm 52
> 00: bad device: 01
>
>
> dimm 53
> 00: bad device: 01
>
>

obviously bad.

> dimm 54
> 00: ad db de c0 01 00 00 00 01 f0 fa fa 00 00 00 d9

Bogus, because the first byte is "how many bytes written". I went to
http://en.wikipedia.org/wiki/Serial_presence_detect#On_older_equipment
and is is clear that 0xad doesn't match what's written:

> 10: 00 00 00 00 00 00 6c 01 00 00 00 00 00 00 00 00
> etc.
> f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

So this is bogus.
>
> dimm 55
> 00: bad device: 01
>
>
> dimm 56
> 00: bad device: 01
>
>

bad.

> dimm 57
> 00: 80 08 08 0d 0a 60 48 00 05 50 60 02 02 08 08 00
> 10: 0c 04 38 00 01 00 01 50 60 50 60 3c 1e 3c 28 40
> 20: 35 47 15 27 3c 28 1e 00 00 37 4b 80 23 2d 0f 00
> 30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 10 6b
> 40: ce 00 00 00 00 00 00 00 01 4d 33 20 39 33 54 33
> 50: 32 35 33 46 5a 30 2d 43 43 43 20 30 46 05 17 46
> 60: 04 cb 50 00 59 42 43 35 36 30 50 00 00 00 00 00
> 70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 80: 00 49 d6 06 71 16 23 33 80 30 45 52 00 07 05 ff
> 90: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> f0: 01 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>

This looks closer to real. 0x80 is a common first byte. It also
matches (almost) the # bytes written since the last 112
bytes of this one are pretty clearly unwritten. Let's dig deeper.

Byte ordering for the first several bytes:

Defines # bytes written into serial memory at module mfgr
Total # bytes of SPD memory device
Fundamental memory type (FPM, EDO, SDRAM...) from appendix A
# Row Addresses on this assembly
# Column Addresses on this assembly
# Module Banks on this Assembly
Data Width of this assembly...
...Data Width continuation
Voltage interface standard of this assembly


next bytes are 08 and 08. Oops. Byte 2 is the type and 8 doesn't match
any type. Disappointing as some of the other
bytes almost look plausible, but 0x60 module banks? Doubtful ...

Time to break out the lm sensors tools ... and do the gpio dance again.

thanks

ron