[RndTbl] d-port daisychains and ryzen ecc

Trevor Cordes trevor at tecnopolis.ca
Wed Feb 13 01:48:09 CST 2019

For those not at the meeting tonight, I just wanted to give a quick report
on some new-ish first-hand tech experience vis a vis Linux support.

- Display-port daisychaining works with Linux (kernel must be fairly new),
and at least the nvidia binary driver (not sure about nouveau, though the
Intel onboard GPU FLOSS drivers are said to support it for sure).  You'd
also need a vidcard that is new-ish with a new enough dport spec.
Probably any decent mid-range card in the last 3 years will do.

  - Final monitor in the chain doesn't need a pass-thru port and can be an
  older dport spec (probably 1.1+)

  - Works great with 2 x 2560x1440 LCDs, but 2 x 4k is probably beyond the
  bandwidth of current widely-available dport spec

- Ryzen (1st and 2nd gen) supports ECC on (certain) normal desktop boards,
like most Asrock ones.  We used Asrock AB350-PRO4.  edac-utils says it
works.  dmidecode hints it works, though with some weird output.
memtest86 (latest version) says it works.  rasdaemon says it works.  It's
rasdaemon that is the replacement for abandon-ware edac-utils.

So there you have it, an option to get a "workstation" with ECC and at
least 1 PCIe x16 (full lanes) slot.  At about half the price of a Xeon
setup, which is the only way to get ECC + x16 slot in Intel land with a
real CPU.  There are some Ryzen teething issues and bios+linux workarounds
you have to do though, so it's not as painless as a Xeon would be.

If anyone knows why dmidecode says this for ram widths, let me know:
	Error Correction Type: Multi-bit ECC
	Data Width: 64 bits
	Total Width: 128 bits

(128 bits!!!!? should be 72)

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