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02-12-2022 09:13 AM
There is a discussion here by our resident memory expert @SDH
I am not sure of your question. Are you asking if you can use ECC?
I am a retired Principal Analyst, and a community volunteer.
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02-13-2022 12:18 PM - edited 02-13-2022 12:33 PM
HP builds its workstations for different segments of the market... the Z420 at time of its development was an entry level workstation vs the large jump in capabilities in the Z620 and the Z820. The Z820 is in a class by itself, but the engineering of the motherboards for the Z420 and the Z620 is very similar. They use a large percentage of identical parts. HP also does an extensive "validation" process for each of these enterprise quality workstations and they look at what is reasonable/affordable to justify running through that expensive process. At the time of initial development, it made sense to leave the Z420 out of some of the loops that the Z620 and Z820 went through both in terms of memory and processors... and HP will only certify parts officially if they have gone through the process thoroughly. So, the Z420 did not get certain parts certified even if those parts work just as well as in their bigger brethren.
Then came along the version 2 of these workstations and the v2 processors which are better/faster/support faster memory than the v1 processors. And, the market has shown that a significant number of us will now choose to run with only one fastest v2 processor because the price on those has become so reasonable. Time passed and the cost of "recycled" processors and memory went way down from what things cost on initial release. Another benefit for us is that HP has used server quality processors and memory, and servers tend to be retired before individual workstations are. So the supply in the market for cross-compatible parts has gone significantly up, and thus the market price has gone way down.
For this reason despite not officially being certified for use in the Z420 v2 specific server memory recycled into the ZX20 v2 workstations works perfectly, at a low cost. I recently checked on ECC buffered ("registered") 1866 MHz 4GB sticks... it was cheaper to buy the same sticks in 8GB size because that was what many of the servers now retired used. Supply more; price less. I can't speak to whether that same memory would work well in a Z420 v1 but I bet it would.
I've posted on exactly the 8GB sticks we used in an upgrade of processor/memory in about 25 Z420 v2 workstations with zero bad recycled sticks. Each box got either 4 or 8 sticks, with cost as low as $11.00 USD/stick (untested sticks). Expect to spend more like 15.00 each, but you can haggle with some leverage if you're buying a set of 8.
For these workstations you always want ECC, and most of us also would only want buffered. Don't mix ranks of memory and for this reason I virtually always stay with a single OEM (such as only Samsung, or only Micron, or only SKHynix, etc.) for a memory set. I'll chose HP-branded sticks with same main OEM codes over others but after doing this a lot I don't mind the same sticks from IBM/Lenovo/Dell servers too. On those codes... there are OEM PDFs you can find that explain what the different parts of the code mean... the last few alphanumerics (factory site, etc.) generally not important when you dig into it.
02-14-2022 06:10 AM - edited 02-14-2022 06:13 AM
as "SDH" pointed out the z420/z620 share many parts, however that's not the whole reason for ECC working on the z420
for ECC to work, the chipset (made by intel) CPU (made by intel) and the Bios (customised by HP) must all support ECC
since the z420/z620 do use the c6xx line chipset which does support ECC (and this can not be disabled)
and both use the same Xeon cpu line which does support ECC (and this can not be disabled)
you are left with the HP bios, which is almost identical between the z420/z640
HP seems to have decided it was not worth the time/money creating/maintaining/supporting two different bios's so they only took the time to certified the z620 for ECC as "SDH" pointed out and left the z420 with ECC enabled but not officially certified as working by HP
this is not unique to HP, i can confirm personally that several Asus systems based on the X99 chipset which supports both the consumer cpu's and the xeons will run registered ECC (when using a xeon cpu)
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