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Old 2019-12-13, 15:29   #1
Xyzzy
 
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What is the current situation for "enthusiast" computers with lots of memory?

Is 128GB or 256GB of memory "affordable" yet?

Edit: We have decided to build a "big memory" computer to use for "scientific" computing.

We are using this thread to determine the appropriate parts to buy and for assistance in building and operating the computer.

We have chosen to buy new parts and to build it ourself rather than buy retired server-grade hardware. We have done this because we like to build and tinker. We also intend to create a "recipe" for others to follow if they want to duplicate.

Overall cost is always a factor but it will not be the only criteria we use to choose parts.

Reliability is the most important attribute we are looking for.

After the box is built, we will run various suggested workloads to benchmark its performance.

We welcome your input!
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Old 2019-12-13, 15:39   #2
kriesel
 
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Depends on what you consider affordable, on the one hand, or acceptable hardware tech on the other. One of the old used systems I bought came with 128GB. Another came with 32 and I subsequently filled another 1/4 of the DIMM slots very economically; 32GB of registered ECC DDR3 was $35. Lots o ram is good for P-1 in prime95/mprime.
Getting an AVX512 system with that much, I've not priced.
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Old 2019-12-13, 17:10   #3
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DDR4 is roughly $4/GB, while DDR3 is less than half that.

DDR3 is used in the Sandy-Bridge and Ivy-Bridge era Xeons, which are pretty old for prime searching purposes (but still okay for NFS factorization projects and ECM).

Whether you want a bunch of memory depends pretty strongly on what you do with the machine. For daily use and prime searching, 16GB is still plenty. As Kriesel says, P-1 and ECM, and NFS post-processing, benefit from more.
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Old 2019-12-13, 17:12   #4
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Not many "enthusiast" chipsets support more than 32GB, right?
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Old 2019-12-13, 17:21   #5
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It looks like a lot of recent mobos support 128 GB, but that much ram is expensive (at least imo).

Here's a cpu/mobo/ram combo, with 128 GB of RAM. The memory is over $500, while the cpu/mobo combo is less than $250.
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Old 2019-12-13, 18:05   #6
chalsall
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Quote:
Originally Posted by VBCurtis View Post
DDR4 is roughly $4/GB, while DDR3 is less than half that.
Just yesterday I bought two sticks of 16GB DDR4 2666Mhz RAM for $189 BDS each, or about $94 USD.

On the other hand, I'm currently typing this in shorts and a light tee-shirt, and I never wear anything but sandals except for running shoes when hashing, or dress shoes for formal meetings...
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Old 2019-12-13, 18:09   #7
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Quote:
Originally Posted by masser View Post
It looks like a lot of recent mobos support 128 GB, but that much ram is expensive (at least imo).

Here's a cpu/mobo/ram combo, with 128 GB of RAM. The memory is over $500, while the cpu/mobo combo is less than $250.
Plus cost of case, power supply, boot drive etc. and integration time.

I can get a used 32-128Gb os-loaded ready to use used system for less than that, with refurb warranty and multiple slots to support fast new gpus. Consider it recycling of the base system. These are not consumer grade, they're vintage very serviceable / maintainable professionals'-workstation towers. Documentation including service manuals tends to be quite good. The new gpus will generally outdo the best of cpus on cost/performance (Radeon VII anyone?). Even non-FMA3 cpus have plenty to do, up to nearly 600M in prime95/mprime. The savings on hardware compared to new pay for the electricity for quite a while (years). Especially when the heat is a winter benefit and more. I do have some oldest hardware that I turn off for the summer (Core 2). Do the economic analysis for your situation, including electrical rate, multiple scenarios of hardware, and winter heating, spring/fall venting waste heat, summer air conditioning additional cost.
I've found that 32GB per prime95/mprime P-1 worker is good to have for bigger exponents. OS, 2 PRPs, 2 P-1s, multiple gpu support, plus user activity fit nicely in 128GB and Windows 10, so are likely to fit well in linux. Not that 64 or less is unworkable; some of mine have 12GB or 8GB and are productive.

Last fiddled with by kriesel on 2019-12-13 at 19:03
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Old 2019-12-13, 18:52   #8
Xyzzy
 
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"Big Memory" Build Guide

Goals:

ECM, P-1 & NFS PP

Requirements:

Reliable
Low maintenance
Bang-for-the-buck
Parts are available through retail channels

Assume the individual would use Linux and run the system headless.

Needed:

Case
MB
PSU
CPU & HSF
Memory
SSD

Questions:

How much $ is "reasonable" to spend?
How much memory?
Is making the build "futureproof/upgradeble" worth considering?
How many cores?
AMD or Intel?
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Old 2019-12-13, 19:27   #9
VBCurtis
 
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Your use interests match well the used workstations that kriesel and I favor. While a used machine would seem to be less reliable than new, the design and resources used in the creation of a $3000+ workstation far exceed the quality and durability of typical build-your-own options.

If I were selecting a machine now for NFS matrices, ECM, and P-1, I would be deciding among HP workstations Z620, Z820, Z640. The main difference between Z620 and Z820 is the 820 has 16 DDR3 slots and a bit larger case- I don't use multiple GPUs, so I can't say for sure if the Z820 has extra slots/space for a multi-GPU setup.
The Z640 is the Haswell-E / DDR4 generation, while Z620 is Ivy Bridge/DDR3. All of these are dual-socket dual-Xeon ECC-memory devices (again, higher reliability).

Cost: Check Ebay. I bought a Z620 a year ago with 64GB (8x8GB with 4 slots open), 750GB disk, dual 10-core 2.6ghz Ivy Bridge Xeons for $900 or so. The Z640 generation will be notably faster because Haswell generation instruction-per-clock is markedly better than any DDR3-era chip; I imagine a dual-8-core Z640 would get more work done per month than my dual-10-core Z620.

Quite a lot of the used listings are for configurations that confuse me; I don't know why a dual-4-core Xeon was a popular choice, nor why someone would lease this level of workstation but put just one 4- or 6- core CPU in it. Lots of the listings are for 4-core ~2.1 ghz 16GB memory configs, while the high-powered ones are pretty rare. When I was shopping, I'd just type the processor name listed into a search page to find out core count/Ghz. Note that on the Z620 in particular, the second CPU socket is on a riser card, and that card is NOT usually included in single-CPU configurations.

For NFS matrices and ECM work, total raw ghz is the best comparison between CPUs; some of the higher-core-count devices run lower Ghz, so aren't meaningfully faster than, say, an 8-core device. Older DDR4-era xeons get ~20% more work done per Ghz than DDR3-era, but are a fair bit more expensive on the used market. These machines are 4 memory channels per socket, from either era.

If I were to stick to new builds only, I'd be looking at 12 core Ryzen, but I'd be asking lots of forum questions and hoping someone else built one and has answers / benchmarks.

Last fiddled with by VBCurtis on 2019-12-13 at 19:39 Reason: word choice & clarity
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Old 2019-12-13, 19:35   #10
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As always, you can trade off specs for price; I don't think there is a magic CPU spec necessary for your desired tasks. 32GB is enough memory for most NFS matrices; only the very biggest need more, such as helping with Greg's 16e queue. Kriesel has written extensively about memory needs for mprime's ECM and P-1. For ECM pretesting related to NFS factorizations, a large B1 like 850M use on the order of 1-1.5GB per thread; again, 32GB is satisfactory even though you might not use every hyperthread for the large bounds all at once.

If I wanted to help with the biggest jobs, I'd go 64GB. Disk is so cheap that I don't care what spec the system comes with; e.g. a 1TB M.2 SSD is under $100.
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Old 2019-12-13, 20:05   #11
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Thanks for the endorsement VBCurtis, although I have little experience with ECM recently and have had little to say about ECM (unlike a lot of other things...) ECM is neither suitable for the GIMPS wavefront nor supported on multimillion-bit lengths with gpu code.

My first forays into gpu computing were mostly on HP Z600s I picked up used, for about $250 each, with dual Xeon X5650 (12 core total), HD, PSU, case, 12GB ram, Win7 Pro, keyboard and mouse included.

Where the HP Z6x0 fall short is in power supply rating, PS efficiency, odd PS shape, and few gpu-side power cables. They're still running years later, although there's been a bit of fade of what the odd special power supply will support, such that boxes that ran 3 or 4 gpus well initially have all been reduced to two gpus each over time.

The Z820 I have came with two dual-width gpus included.

The Thinkstation line uses a standard rectangular brick PSU, so seems more maintainable through multiple motherboard generations if one wants to go the kit building approach later.

Another route that I think George has adopted lately is the cryptocoin miner frame approach. Gpus are becoming dominant, and need lots of cooling air. It doesn't take much of a motherboard or cpu to keep a gpu or several well fed.
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