Cheap EPYC Rome 7742 and 7402 for sale.

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pututu
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Cheap EPYC Rome 7742 and 7402 for sale.

Post by pututu » Sun Sep 26, 2021 10:09 am


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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sun Sep 26, 2021 11:31 am

I was just coming here to post this after seeing it. I sent them a PM asking if those EPYC 7742's are vendor locked to Dell or otherwise. The 24 core one would probably work well for my 'multiple GPU crunching machine' build even.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sun Sep 26, 2021 4:33 pm

I just sent money over for the 7742's

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by crashtech » Sun Sep 26, 2021 5:09 pm

Wow, Ice! Nice score!

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sun Sep 26, 2021 5:39 pm

crashtech wrote:
Sun Sep 26, 2021 5:09 pm
Wow, Ice! Nice score!
Thanks!

I guess now I need to figure out what to do with them. @StefanR5R any suggestions? I'd like to throw them both in one machine unless there are any major performance benefits to building 2 separate machines. This would seem to be the logical motherboard to use? - https://www.newegg.com/asrock-rack-rome ... klink=true

Noctua heatsink/fan preferably but I'm not sure what the best one is that is compatible. Any RAM suggestions?

This is definitely uncharted territory for me.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Skillz » Sun Sep 26, 2021 6:17 pm

One benefit to building two separate setups instead of 2 CPUs on one is more PCI-e lanes for GPUs when using two separate systems. Since 1 CPU should be enough to handle the PCIe lanes for maximum GPUs, adding a second CPU to the same system wont give you more GPU slots.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by crashtech » Sun Sep 26, 2021 7:41 pm

I'm always thinking about density, but it's certainly true that 2 systems would allow more GPUs.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Mon Sep 27, 2021 1:44 am

Icecold wrote:
Sun Sep 26, 2021 5:39 pm
@StefanR5R any suggestions?
Unlike most DCers, I basically have two separate types of computers: 1) Headless high-core-count computers, 2) GPU-equipped low-core-count computers. There are a few reasons for and against this approach, and I am sure you already thought about this for your own computer zoo.
Icecold wrote:
Sun Sep 26, 2021 5:39 pm
I'd like to throw them both in one machine unless there are any major performance benefits to building 2 separate machines.
Under Linux, there shouldn't be a performance impact from 2P compared to 2x 1P at least for CPU-only projects. On Windows, you may need 2 client instances (or multiples of 2) with CPU affinity enforced to one socket each.

I have no insight into GPU application performance on 2P systems.
Icecold wrote:
Sun Sep 26, 2021 5:39 pm
This would seem to be the logical motherboard to use? - https://www.newegg.com/asrock-rack-rome ... klink=true
I went with mainboards which have only 1 Gbit NICs and PCIe 3 myself because I have no need for better I/O and wanted to cut down on power consumption of the remaining (mostly idle) I/O components. The difference between idle 1GbE/10GbE and idle PCIe3/PCIe4 probably isn't much though.

If you want to use GPUs but won't use PCIe risers, some Supermicro boards are not suitable because of conflicts between onboard connectors and GPU coolers.
Icecold wrote:
Sun Sep 26, 2021 5:39 pm
Noctua heatsink/fan preferably but I'm not sure what the best one is that is compatible.
Of the mainstream DIY TR4/SP3 air coolers, only Noctua coolers are worthwhile according to the tests which I have seen. Use the 140 mm version unless you have height restrictions.

Thanks to an optional lateral offset in the mounting kits of Noctua TR4/SP3 coolers, they should fit on most 2P mainboards. I checked cooler geometry and board geometry based on vendor drawings before I bought mine.

You must provide ample air flow across or top-down the VRM section(s), and reasonable air flow at RAM, NIC, and M2 SSD. I placed a whole collection of fans of various diameters on top of such board areas for this reason. And of course I have case fans which force front-to-back air flow (even though some of my 2P computers don't have a case, just a shelf and dividers in the shelf as air guides).
Icecold wrote:
Sun Sep 26, 2021 5:39 pm
Any RAM suggestions?
IMO it's worthwhile to populate all 8 channels per CPU. If you don't want that, populate 4. (Not 2, and definitely not 6. Reasonable support for 6 channels per socket started with Epyc 7003 Milan. With Rome, 6-channel RAM performs worse than 4-channel RAM. All arbitrary 1-, 3-, 5-, 7-channel populations work too but have similar performance drawbacks.)

My 2x32-core ( = 128 threads total) computers have 256 GBytes RAM which was always sufficient so far. I don't know if you can get by with 256 GB in a 2x64-core or 128 GB in a 1x64-core computer, or would eventually need 512 or 256 GB respectively; never really looked into this.

I went with DDR4-3200 for Epyc Rome myself, i.e. the top possible speed, but merely out of principle, not based on particular performance measurements.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Mon Sep 27, 2021 6:20 am

I appreciate the information. I kind of muddied the water by mentioning my multiple GPU builds but this will most likely be a CPU cruncher only. I like having high thread count machines without GPU's. It will run Linux.

I think I'm going to just order a motherboard and CPU coolers and hold off on the ram for now. I have ecc ddr4 here I can pull from another machine to test but I don't want to invest the extra money until I get the processors and confirm they're not vendor locked.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by cellarnoise2 » Mon Sep 27, 2021 10:02 pm

Best of luck Lukewarm!

Even if they are vendor locked this is a good price and even if you need to sell you should get back what you have put into them in the near future.

I think the board you are looking at is good as there are not many options and the additional external I.O. does not suck too many watts nowadays.

From what I have been reading on Serve the Home and other sites is that the dual boards work well with the 140mm Noctua coolers and additional airflow in a case over the VRMs with the OEM cpus. The ES versions you can overclock and that can really push the heat into the VRMs as we all know. These appear to be stock and hopefully not vender locked....

More power to the Team!!!! but now I need to catch up even more :)

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Skillz » Mon Sep 27, 2021 10:15 pm

cellarnoise2 wrote:
Mon Sep 27, 2021 10:02 pm
Even if they are vendor locked this is a good price
If it's vendor locked then you can only use a vendor (Dell) branded Motherboard with them and even then, they might not work. So essentially you'll have a $1000 (or however much they cost) paperweight.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by cellarnoise2 » Tue Sep 28, 2021 12:40 am

Vendor locked these are going for a $1,000+ each, the nonES versions on several reseller sites. I don't know why, but they seem to be selling for this or more. Even advertised as locked to a vendor. I have not tracked what they go for locked to a a specific vendor though.

The next round of workstation and server cpus are coming soon, so hope they work or sell them soon.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Tue Sep 28, 2021 5:28 am

The seller had posted 'I guarantee everything works for two weeks after you receive it to give you time to set it up and test.' and had also reiterated that via PM, so if they do not function in my motherboard I think he would probably let me send them back for a refund.

I should know in a few days, maybe this weekend. The main hold up will be waiting on the motherboard to arrive, but I ordered that and everything else other than RAM yesterday. I will pull RAM from another machine to test, I didn't want to drop $1500+ on RAM just to find out the CPU's aren't going to work with my motherboard.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Tue Oct 05, 2021 8:46 am

StefanR5R wrote:
Mon Sep 27, 2021 1:44 am
I went with DDR4-3200 for Epyc Rome myself, i.e. the top possible speed, but merely out of principle, not based on particular performance measurements.
Do you think it's likely DDR4-2400 would be a bottleneck for this build? My thought process being that with 8 channel memory the memory speed should matter less, but I wasn't really sure.

Edit - doesn't matter, was able to purchase DDR4-3200 at a decent price.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Thu Oct 07, 2021 2:23 am

8 channels aren't really much for 64 cores though.

Back when I routinely had 14-core and 22-core BDW-EPs running the same projects at the same times, I did of course see projects in which throughput / (core count × clock) was the same between them, and others which did not scale as well to the 22-core Xeons. Rosetta@home was one of the latter kind, but there were more. Alas I didn't pursue this topic systematically while I still had the 14-core Xeons in operation.

Apparently, PrimeGrid LLR projects are a counter example which are not dependent on RAM bandwidth once you dialed in the right combination of simultaneously running LLR instances and thread count. Here is my most recent PrimeGrid LLR offline test (321-LLR) with results for both types of Xeons, each with 2×4 channels of DDR4-2400c17:
…dual 14-core Xeons: 215 kPPD / (56 used threads × 2.9 GHz) = 1.32 kPPD/thread/GHz
…dual 22-core Xeons: 299 kPPD / (84 used threads × 2.6 GHz) = 1.37 kPPD/thread/GHz
…dual 22-core Xeons: 299 kPPD / (88 available threads × 2.6 GHz) = 1.31 kPPD/thread/GHz
The "available threads" figure is the more significant one, because the use of SMT in LLR has the only purpose to help saturate the FMA units. I.e. the calculation should actually be kPPD / (available FMA units × clock).
But of course the further you are off of the optimum configuration for a given PrimeGrid LLR subproject, the more dependent on RAM performance it becomes.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Thu Oct 07, 2021 8:33 am

I'm glad I went with the DDR4-3200 then. I would have always been wondering if my RAM was hindering performance.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Sat Oct 09, 2021 4:04 am

BTW, most EPYC models have a configurable TDP: Rome SKUs overview at servethehome

In the AMI BIOS which Supermicro uses, it's in "Advanced" -> "NB Configuration". I have no idea if and where it can be found in ASRock's BIOS; perhaps somewhere in "Advanced" -> "AMD CBS". AMD recommends to set TDP and PPT to the same value.

AMD has got a few guides about a variety of more BIOS parameters: Performance Tuning Guides
Particularly, see "Workload Tuning Guide for AMD EPYC™ 7002 Series Processor Based Servers" at the bottom of this list.

And one other thing: Fan speed control — that's of course different between motherboard vendors. But I think the vendors have in common that they can't be bothered to document it. Here is some good info on Supermicro's implementation. I haven't looked for ASRock specific info.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sat Oct 09, 2021 4:17 am

I will definitely read through that - thanks! I posted this other places in the forum, but in case you hadn't read those - I initially thought either the processor or motherboard might have an issue since it would always error on Ram slot B1. I was going to flip flop the processors to determine if it would follow the processor or socket, but decided just to try to reseat the processor. I cleaned the contacts and reseated it and everything seems good now. I rebooted it a few times when installing the OS and it always detects all 16 sticks of RAM. I ran Yoyo overnight and so far no issues. It was quite a relief when it started detecting that RAM slot.

I have 120MM fans pointed at the VRM's currently but they're not super high airflow. 'Vcore1 MOS Temp' in the BMC shows 65 degrees - that seems maybe somewhat high to me. Any thoughts on if that's too high?

I'm pretty sure the RAM is running correctly in 8 channel, I run sudo dmidecode --type memory in linux and it goes up to "bank locator P0 Channel H' and 'bank locator P1 Channel H' which I think means it's running in 8 channel.

I appreciate all the info you provided on how the BMC works.. I'm kicking myself for never using that before. I have a few Xeons that have a BMC and never bothered with it because I never realized how incredibly useful it is. I doubt I'll buy a motherboard without one moving forward unless it's my main workstation PC.

On that fan control doc - I somewhat assumed that fan 0 and 1 would be the CPU fans so that is how I plugged mine in. It would be logical that the first fans would be CPU fans so that's what I went with.

Any suggestions on what to set the PPT to? I have most of my 16 core/32 thread AMD processors set to 95 watts.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Sat Oct 09, 2021 4:46 am

Icecold wrote:
Sat Oct 09, 2021 4:17 am
I have 120MM fans pointed at the VRM's currently but they're not super high airflow. 'Vcore1 MOS Temp' in the BMC shows 65 degrees - that seems maybe somewhat high to me. Any thoughts on if that's too high?
I don't actually know, but I believe that's OK for continuous operation.

On my H11DSi board, I have one Noctua NF-A4x20 sitting on the VRM heatsink which covers the VRM area of both CPUs. Another 80 mm fan which sits on some of the RAM banks also reaches a little bit over that heatsink.

When I ran PrimeGrid (at IIRC 2x 180 W PPT/TDP), CPU VRM temperature was 70…72 °C at 3900 RPM of the 40 mm fan and I don't know which ambient temperature. It was with open windows, making for different temperature zones and layers within the living room. :-)

Now with SiDock at 2x 155 W PPT/TDP but actual consumption only 335 W at the wall, CPU VRM temps are 60…61 °C, with 2600 RPM of the 40 mm fan and maybe 24 °C room temperature where this computer sits.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sat Oct 09, 2021 4:55 am

I'll probably try to refine this setup a bit. I just threw a couple random extra 120mm fans I had sitting around, and don't even currently have them cable tied or anything they're just sitting in there.

I can't get over how great being able to access the BMC is. Any time anybody posted PPT figures here such as "tested at ____ PPT" I thought "man I can't imagine having to haul a physical keyboard/mouse/monitor over to _____ machine to get in the bios to test that". Being able to do that across the LAN is game changing for me. I have no idea why I was ignorant about that for so long(while purchasing machines advertising IPMI here and there, seeing posts here about it, etc.) but it's fantastic.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Sat Oct 09, 2021 6:13 am

Icecold wrote:
Sat Oct 09, 2021 4:17 am
Any suggestions on what to set the PPT to? I have most of my 16 core/32 thread AMD processors set to 95 watts.
7742's possible range of 225…240 W isn't as "wide" as the 155…180 W range of my 7452s, let alone the ranges of PPTs within which you can drive Ryzens. I suspect the efficiency loss when you go from the minimum and default 225 W to the maximum of 240 W is negligible. So if the VRM temps are OK for you at the latter (when you put a load on it which really utilizes it, e.g. a "small FFT" load like maybe PrimeGrid Sophie Germain singlethreaded on all physical cores), then I'd say you might as well set-and-forget it to 240 W PPT and TDP.

Added in 4 minutes 34 seconds:
PS, AMD tell us in their "Workload Tuning Guide for… 7002 series" to switch cTDP and package power limit to "OPN Max" when we run HPC type workloads.

Added in 14 minutes 25 seconds:
Icecold wrote:
Tue Oct 05, 2021 8:46 am
Do you think it's likely DDR4-2400 would be a bottleneck for this build? My thought process being that with 8 channel memory the memory speed should matter less, but I wasn't really sure.

Edit - doesn't matter, was able to purchase DDR4-3200 at a decent price.
Here is what the "Workload Tuning Guide" says on the matter:
AMD wrote:2.2.3 Memory Clock Speed
Benefit: By default, the BIOS for EPYC 7002 Series processors will run at the maximum allowable clock frequency by the platform. This configuration results in the maximum memory bandwidth for the processor, but in some cases, it may not be the lowest latency. The Infinity Fabric will have a maximum speed of 1467 MHz (lower in some platforms), resulting in a single clock penalty to transfer data from the memory channels onto the Infinity Fabric to progress through the SoC. To achieve the lowest latency, you can set the memory frequency to be equal to the Infinity Fabric speed. Lowering the memory clock speed also results in power savings in the memory controller, thus allowing the rest of the SoC to consume more power potentially resulting in a performance boost elsewhere, depending on the workload.

[...]
3.4 HPC and Telco Settings
[NUMA and MemorySettings/ Memory Clock Speed]
CFD & Other Memory Bound: Auto
Chem, Physics & Other SIMD Bound: Try 1467

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by pututu » Sat Oct 09, 2021 10:32 am

@Icecold , time to post your monster rig. Here is someone else build with dual 7742 and four RTX 3080 in servethehome forum https://forums.servethehome.com/index.p ... ost-294380

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Icecold » Sat Oct 09, 2021 11:24 am

It's about as generic as they come. Cheapest Coolermaster case that supported EEB motherboards. No video card. Superflower 850w power supply. Noctua Heatsink/fans. Cheap SK Hynix NVMe 1TB SSD. Crappy cheap 120mm fans propped up wherever to keep the VRM's with air flowing over them. That's the last step is get better fans and secure them somehow near the VRM's. Servethehome is another forum I need to register for :lol: I look at it occasionally but never registered.
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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by StefanR5R » Sat Oct 09, 2021 2:50 pm

My dual-processor computers either sit on a piece of cardboard, or are crammed into a compact (midi) ATX tower case. The selection of compact ATX cases with a flat back plate (required to accommodate larger than ATX boards) is small though. I even thought of using µATX cases for this purpose, and mounting the PSU rotated over the unused PCIe slot area, but never found a suitable µATX case.

I also looked for rackmount cases but never found one which isn't very deep but, importantly, is high enough to fit the 140/150mm class tower coolers.

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Re: Cheap EPYC Rome 7742 and 7402 for sale.

Post by Skillz » Sat Oct 09, 2021 3:09 pm

StefanR5R wrote:
Sat Oct 09, 2021 2:50 pm
I also looked for rackmount cases but never found one which isn't very deep but, importantly, is high enough to fit the 140/150mm class tower coolers.
They used to make some cheap 4U cases that you could use the server boards in. Then just take a dremel (or whatever similar tool they have in Germany) and cut out holes for the tower coolers to stick out of.

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