Server CPU Sockets

I am always looking for ways of increasing the compute power I have at a reasonable price. I am very happy with my HP z840 dual CPU workstation [1] that I’m using as a server and my HP z640 single CPU workstation [2]. Both of them were available second hand at quite reasonable prices and could be cheaply upgraded to faster CPUs. But if I can get something a lot faster for a reasonable price then I’ll definitely get it.

Socket LGA2011-v3

The home server and home workstation I currently use have socket LGA2011-v3 [3] which supports the E5-2699A v4 CPU which gives a rating of 26,939 according to Passmark [4]. That Passmark score is quite decent, you can get CPUs using DDR4 RAM that go up to almost double that but it’s a reasonable speed and it works in systems that are readily available at low prices. The z640 is regularly on sale for less than $400AU and the z840 is occasionally below $600.

The Dell PowerEdge T430 is an ok dual-CPU tower server using the same socket. One thing that’s not well known is that is it limited to something like 135W per CPU when run with two CPUs. So it will work correctly with a single E5-2697A v4 with 145W TDP (I’ve tested that) but will refuse to boot with two of them. In my test system I tried replacing the 495W PSUs with 750W PSUs and it made no difference, the motherboard has the limit. With only a single CPU you only get 8/12 DIMM sockets and not all PCIe slots work. There are many second hand T430s on sale with only a single CPU presumably because the T330 sucks. My T430 works fine with a pair of E5-2683 v4 CPUs.

The Dell PowerEdge T630 also takes the same CPUs but supports higher TDP than the T430. They also support 18*3.5″ disks or 32*2.5″ but they are noisy. I wouldn’t buy one for home use.

AMD

There are some nice AMD CPUs manufactured around the same time and AMD has done a better job of making multiple CPUs that fit the same socket. The reason I don’t generally use AMD CPUs is that they are used in a minority of the server grade systems so as I want ECC RAM and other server features I generally can’t find AMD systems at a reasonable price on ebay etc. There are people who really want second hand server grade systems with AMD CPUs and outbid me. This is probably a region dependent issue, maybe if I was buying in the US I could get some nice workstations with AMD CPUs at low prices.

Socket LGA1151

Socket LGA1151 [5] is used in the Dell PowerEdge T330. It only supports 2 memory channels and 4 DIMMs compared to the 4 channels and 8 DIMMs in LGA2011, and it also has a limit of 64G total RAM for most systems and 128G for some systems. By today’s standards even 128G is a real limit for server use, DDR4 RDIMMs are about $1/GB and when spending $600+ on system and CPU upgrade you wouldn’t want to spend less than $130 on RAM. The CPUs with decent performance for that socket like the i9-9900K aren’t supported by the T330 (possibly they don’t support ECC RAM). The CPUs that Dell supports perform very poorly. I suspect that Dell deliberately nerfed the T330 to drive sales of the T430.

The Lenovo P330 uses socket LGA1151-2 but has the same issues of taking slow CPUs in addition to using UDIMMs which are significantly more expensive on the second hand market.

Socket LGA2066

The next Intel socket after LGA2011-v3 is LGA2066 [6]. That is in The Dell Precision 5820 and HP Z4 G4. It takes an i9-10980XE for 32,404 on Passmark or a W-2295 for 30,906. The variant of the Dell 5820 that supports the i9 CPUs doesn’t seem to support ECC RAM so it’s not a proper workstation. The single thread performance difference between the W-2295 and the E5-2699A v4 is 2640 to 2055, a 28% increase for the W-2295. There are “High Frequency Optimized” cpus for socket LGA2011-v3 but they all deliver less than 2,300 on the Passmark single-thread tests which is much less than what you can get from socket LGA2066. The W-2295 costs $1000 on ebay and the E5-2699A v4 is readily available for under $400 and a few months ago I got a matched pair for a bit over $400. Note that getting a matched pair of Intel CPUs is a major pain [7].

Comparing sockets LGA2011-v3 and LGA2066 for a single-CPU system is a $300 system (HP x640) + $400 CPU (E5-2699A v4) vs $500 system (Dell Precision 5820) + $1000 CPU (W-2295), so more than twice the price for a 30% performance benefit on some tasks. The LGA2011-v3 and USB-C both launched in 2014 so LGA2011-v3 systems don’t have USB-C sockets, a $20 USB-C PCIe card doesn’t change the economics.

Socket LGA3647

Socket LGA3647 [8] is used in the Dell PowerEdge T440. It supports 6 channels of DDR4 RAM which is a very nice feature for bigger systems. According to one Dell web page the best CPU Dell officially supports for this is the Xeon Gold 5120 which gives performance only slightly better than the E5-2683 v4 which has a low enough TDP that a T430 can run two of them. But according to another Dell web page they support 16 core CPUs which means performance better than a T430 but less than a HP z840. The T440 doesn’t seem like a great system, if I got one cheap I could find a use for it but I wouldn’t pay the prices that they go for on ebay. The Dell PowerEdge T640 has the same socket and is described as supporting up to 28 core CPUs. But I anticipate that it would be as loud as the T630 and it’s also expensive.

This socket is also used in the HP Z6 G4 which takes a W-3265 or Xeon Gold 6258R CPU for the high end options. The HP Z6 G4 systems on ebay are all above $1500 and the Xeon Gold 6258R is also over $1000 so while the Xeon Gold 6258R in a Z6 G4 will give 50% better performance on multithreaded operations than the systems I currently have it’s costing almost 3* as much. It has 6 DIMM sockets which is a nice improvement over the 4 in the z640. The Z6 G4 takes a maximum of 768G of RAM with the optional extra CPU board (which is very expensive both new and on ebay) compared to my z840 which has 512G and half it’s DIMM slots empty. The HP Z8 G4 has the same socket and takes up to 3TB of RAM if used with CPUs that support it (most CPUs only support 768G and you need a “M” variant to support more). The higher performance CPUs supported in the Z6 G4 and Z8 G4 don’t have enough entries in the Passmark database to be accurate, but going from 22 cores in the E5-2699A v4 to 28 in the Xeon Platinum 8180 when using the same RAM technology doesn’t seem like a huge benefit. The Z6 and Z8 G4 systems run DDR4 RAM at up to 2666 speed while the z640 and z840 only to 2400, a 10% increase in RAM speed is nice but not a huge difference.

I don’t think that any socket LGA3647 systems will ever be ones I want to buy. They don’t offer much over LGA2011-v3 but are in newer and fancier systems that will go for significantly higher prices.

DDR5

I think that DDR5 systems will be my next step up in tower server and workstation performance after the socket LGA2011-v3 systems. I don’t think anything less will offer me enough of a benefit to justify a change. I also don’t think that they will be in the price range I am willing to pay until well after DDR6 is released, some people are hoping for DDR6 to be released late this year but next year seems more likely. So maybe in 2027 there will be some nice DDR5 systems going cheap.

CPU Benchmark Results

Here are the benchmark results of CPUs I mentioned in this post according to passmark.com [9]. I didn’t reference results of CPUs that only had 1 or 2 results posted as they aren’t likely to be accurate.

• [1] https://etbe.coker.com.au/2025/04/05/hp-z840/
• [2] https://etbe.coker.com.au/2025/04/05/hp-ml110-gen9-z640/
• [3] https://en.wikipedia.org/wiki/LGA_2011
• [4] https://tinyurl.com/2ddumsfe
• [5] https://en.wikipedia.org/wiki/LGA_1151
• [6] https://en.wikipedia.org/wiki/LGA_2066
• [7] https://etbe.coker.com.au/2025/06/19/matching-intel-cpus/
• [8] https://en.wikipedia.org/wiki/LGA_3647
• [9] https://www.passmark.com/