[coreboot] Coreboot ECC support in Asrock IMB-A180-H

[Alberto Bursi]

On 09/07/2017 01:24 PM, Kyösti Mälkki wrote:
> On Thu, Sep 7, 2017 at 1:40 PM, Nico Huber <nico.h at gmx.de> wrote:
>> Hello Alberto,
>>
>>   On 09/06/2017 09:30 PM, Alberto Bursi wrote:
>>> I've stumbled upon a Asrock IMB-A180-H board (a eKabini-based
>>> "industrial" mini-itx motherboard) on ebay and since it is supported by
>>> Coreboot I was considering about purchasing it.
>>>
>>> The APU onboard supports ECC ram (ECC so-dimms are kinda rare but I can
>>> find them), while of course the Asrock site does not say anything about
>>> ECC support (how unexpected).
>> it's rather unlikely that a board supports it when the manufacturer
>> doesn't mention it. ECC support needs additional traces on the main-
>> board (as the bus is 72 bits wide instead of 64 bits). So just having
>> compatible chips doesn't suffice.
>>
> See JEDEC Module 4.20.18 vs 4.20.21 standards.
>
> SODIMM 204-pin socket pinout for 64bit non-ECC vs 72bit ECC is already
> different.
> Some ground pins have been sacrificed to fit those extra ECC bits in the socket.
> In other words: no amount of open source will give you ECC SO-DIMM support when
> PCB was designed otherwise.
>
> That board is one of eKabini reference desings, schematics check tells me ECC
> pins of the APU SOC part are not connected.
>
> Kyösti

Thanks a lot for the information! :)
I had some suspicions about socket/board support too as I think also 
DIMMs have the same issue.

Since I really wanted ECC capability, I'll probably get a PCEngines APU 
with 4GB of RAM, which was designed for ECC and seems to have it enabled 
in their stock firmware (coreboot-based) from the feedback I saw.
 From the schematics https://pcengines.ch/schema/apu2c.pdf it seems they 
have one screen port connected to a pinout on the board, although stock 
firmware disables it to use less power. Can do without screen too if I 
can't hack it, it's main usage will be network infrastructure anyway. 
Was just a nice bonus.

-Alberto