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

[Kyösti Mälkki]

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