[SOLVED] HP z840 possible downgrade from dual-CPU v3 to single-CPU v4

[Mycelium]

Hi,

Quick summary: I have a dual CPU HP z840 which is too powerful. I would like to downgrade to save power. Wonder about the compatibility of the CPUs I plan to replace.

Longer introduction:

• HP z840, 2x E5-2678 v3 (2x12 cores = 24 cores, 48 threads), rated 120W per CPU
• 128 GB ram (8x16GB DDR4 ECC)
• 1 NVMe 1TB using an after market adaptor NVMe-PCIe
• low end video card

Bought that machine on eBay 3 years ago for learning Kubernetes, mostly to experiment with a local cluster with VMs using KVM. I no longer need that much power as I can use cloud provider or working directly with the Kubernetes clusters at work.

Now I basically use that machine as my workstation (Debian 12, KDE) for work. I could repurpose it to become a home server. The problem is that this HP z840 is too power hungry. Measuring with a watt meter at the wall, it idles at 60W. When working it fluctuates between 125 - 170W. I have modest needs for home server, for which I currently use a more power efficient machine.

I like that HP z840 and would like to continue to use it as workstation. But I would like to reduce the power consumption. The main usage is programing, scripting. I rarely use more than 16GB of ram, the CPUs are mostly idle most of the time. The most intensive tasks is when I run temporarily a linux VM or two with KVM.

QUESTIONS

Q1. Is it OK to replace the two E5-2678 v3 by one E6-2620 v4 (8 phys cores) or one E6-2630 v4 (10 phys cores). Please note, there is a jump in generation v3 -> v4.

For some reasons, in spite of the 8 vs 10 cores both of these CPUs are rated for a 85W TDP. In this case it would make more sense to go with 10 cores. I am aware that the lack of a 2nd CPU would disable half of the RAM banks and some PCI slots would no longer work.

This is OK, reducing 128 to 64GB ram is plentiful enough for my usage. I use only 2 PCI slots (the adapter for NVMe, video card).

Q2. on eBay, I could find the E5-2620v4 or E5-2630v4 for about $10 from sellers from China, free shipping. Is it legit? Not sure why the price is so low.

Thanks very much for any help

EDIT (answers)

Ordered from eBay 2x E5-2630 v4, stepping SR2R7, $13 for both, free shipping, delivered in a week. Maybe it was on sale, b/c the price is now doubled of what I had ordered.

Replaced the existing 2x E5-2678 v3. Rebooted the HP z840 (bios 2.61, up-to-date as of Aug 2023). The new CPUs are recognized by the BIOS. The BIOS has a hardware diagnostic utility. I ran the 30 minutes CPU test which was successful. Then ran Memtest86+ for 4 hours which also passed.

Overall the computer was working as before. But the goal of hoping to see a significant power consumption reduction is not really there. Luckily for me, it was not a very expensive experiment. The average power consumption is lowered by around 10W. Was 125W now 115W. The usage is typical programming work (no intensive workload), web browsing, Debian 12, KDE.

Looking forward to reducing the power consumption by half when I will run in single CPU mode.

 

[nexox]

I don't know anything about that particular HP, but most machines that run E5 v3 can do v4 with a BIOS update, and those v4 CPUs (really any of them other than the top SKUs) are quite cheap. If you're in the US I would suggest getting the CPU used from a US seller, ships faster and if there are any issues it'll be easier to resolve them (edit: and I just checked, they're under $5 from reputable ebay sellers.)

 

[RolloZ170]

I could find the E5-2620v4 or E5-2630v4 for about $10 from sellers from China, free shipping. Is it legit?

yes.

Not sure why the price is so low.

if it is too low for you i can sell you one for much more.

update the BIOS with the V3s first.

 

[Mycelium]

Thanks gentlemen. If the cheap price of those Xeon v4 on eBay are legit, let me give a try.

Still wonder why a Xeon could cost that low. On local ads, I see people selling old Intel Core i3, i5, i7 for way more than $10.

 

[nexox]

Enterprise stuff is like that, big organizations are now retiring systems one or two generations newer than the v4 Xeons, which have been phased out in huge quantities, so there are a whole lot of used CPUs and most potential buyers for used server parts want something newer, or at least with more cores/GHz.

I forgot to mention, but TDP is not going to tell you much about idle power consumption, the 8 core part will almost certainly use a bit less at idle.

 

[RolloZ170]

On local ads, I see people selling old Intel Core i3, i5, i7 for way more than $10.

there is a difference between offer and sell.

 

[rtech]

HPE has quite extensive documentation about its workstations so you should check that first.

 

[Mycelium]

Hi,

Experiment successful, 2x E5-2678 v3 replaced by 2x E5-2630 v4. Total cost $13 USD. Original post updated with the answer.