20170518, 01:17  #1 
May 2016
1 Posts 
Purpose Built rig?
Hi. So far through various accounts I have contributed about over14K gHz/days... over the last... 6? years.
The thought had come to mind to build a purpose built gpu? rig to crunch numbers all day long... Have any ideas / sugestions? Is there a thread I should check out / missed? Thanks! Chris 
20170518, 13:23  #2 
"/X\(‘‘)/X\"
Jan 2013
2923_{10} Posts 
For doing LL as cheaply and efficiently as possible, see the George's dream build thread. The short version is to buy i57500 with dual rank, dual dimm DDR42400 and put four of them on the cheapest Gold rated power supply using cable splitters.
For LL speed, high end Xeons are best. AMD Zen isn't bad, but due to implementation details of Zen you get only half the performance per core. For Trial Factoring on GPUs, the 1080 Ti is currently king. You can compare GPU TF rankings here. Trial Factoring is the most efficient use of GPUs. For LL on GPUs, the 1080 Ti is also the best of the new cards. You can compare GPU LL rankings here. If your electricity is free, or you use electric heat in the winter, then that changes game a little bit. Old Nvidia Fermi GPUs are very fast at TF, and you can often find GTX 580's for cheap. The original Titan is also great for LL. If you're on a budget, the RX 470 isn't bad. If you want to run multiple GPUs though, and have to pay for supporting hardware like power supplies and PCIe slots, going with 1080 or 1080 Ti will be cheapest. 
20170518, 13:40  #3 
(loop (#_fork))
Feb 2006
Cambridge, England
2·3·29·37 Posts 
LL on GPUs is strictly inferior to LL on secondhand Sandy Bridge Xeons  you can buy two whole boxes for the price of a GTX1080 card, they use only a bit more electricity and they LL significantly faster. I assure you I'm not being paid to recommend http://www.bargainhardware.co.uk/qua...guretoorder/
(OK, they are not great things to share a room with, I am lucky enough to be able to confine them to an outbuilding) 
20170519, 09:06  #4 
Romulan Interpreter
Jun 2011
Thailand
2^{4}·13·47 Posts 

20170519, 16:45  #5 
"Curtis"
Feb 2005
Riverside, CA
1001101111111_{2} Posts 

20170519, 21:18  #6 
"/X\(‘‘)/X\"
Jan 2013
37·79 Posts 

20170519, 23:14  #7 
"David"
Jul 2015
Ohio
11·47 Posts 
According to the mersenne.org benchmarks, a core of the 5650@2.67GHz is good for either 56 or 66ms/iteration at 4M FFT. I will give the benefit to the 5650 and say 56, giving 17.86 iterations/second. For ease of comparison, I will make iters/second@4M FFT my metric of performance.
Even though it isn't usually accurate, lets say we can scale all six cores perfectly and achieve 107.14 iters/s per chip. That would give your dualX5650 214.28 iters/s best case. (On a 5930K Haswell 6 core chip, going from 1 to 6 cores is about 22% slower, so 175.64 iters/s is probably more likely for the pair of X5650s) This is a 6 core chip with a 95W TDP, and the $269.99 system on eBay uses a 650W power supply. HP itself estimates your total system TDP at max load is 282W (Seems reasonable). 771408 iters/h for 282W ~= 2735.5 iterations per Watt. There is a pair of Titan Blacks on eBay right now for $500, so $250ea. Timings at 4M are 2.56ms/iter, or 390 iter/s. Power consumption is a full 250W, plus a host system of around 100W. You will probably need to spend at least $200 on that host system too, but why not buy the $269 Xeon's above and use one PCIe slot to double your throughput with a GPU. A RX480 pulls 3.657ms/iter @4M(273 iters/sec). The RX580 a bit faster (~294 iter/s) and sells for ~$290 new, looks like $200250 on eBay. This will pull about 165 watts. A Fury X achieves 2.2ms/iter @4M (454.5 iter/sec) at 250W and sells for about $630. An R9 Nano 2.7ms/iter (370 iter/sec) at about 180W and sells for $420 Dual Sandy Bridge Xeons: Initial Cost: $270 Est. cost to run for 1 year: 282W *24*365.25 = 2472 kWh @ $0.10): $247.20 Iterations (Ideal): ~6,762,000,000 ~= about 91.4 74M Exponents Cost per 74M exponent: $5.66 Incremental cost per exponent: $2.70 All GPU Host System initial cost (No cycles contributed): $250 Titan Black: Initial Cost: $250 + $250 = $500 Est. cost to run for 1 year: ((250W+100W host) * 24 * 365.25 = 3068 kWh @ $0.10): $306.80 Iterations (Real): ~12,307,464,000 ~= 166.32 74M Exponents Cost per 74M exponent: $4.85 Incremental cost per exponent: $1.84 RX580 Initial Cost: $290 + $250 = $540 Est. cost to run for 1 year: ((165W+100W host) * 24 * 365.25 = 2323 kWh @ $0.10): $232.30 Iterations (Real): ~9,277,934,400 ~= 125.38 74M Exponents Cost per 74M exponent: $6.16 Incremental cost per exponent: $1.85 Fury X: 193.8 74M exponents, $6.12/per, $1.58 incremental. Fury Nano: 157.8 74M exponents, $5.80/per, $1.55 incremental. So it all depends on how cheap your power is, and how long you plan to operate the hardware. Note that I was intentionally biased towards the Sandy Bridge (Top performance numbers, minimal power specs). In reality you could put 34 GPUs in one 100W host and drop your incremental $/exponent down to $1.14 or so. Last fiddled with by airsquirrels on 20170519 at 23:16 
20170520, 01:17  #8 
"Curtis"
Feb 2005
Riverside, CA
7×23×31 Posts 
The sort of awesomeness you posted for this comparison makes me really happy that (1) I asked, and (2) that I'm wrong.
Thank you very much! p.s. each CPU has 3 channels of DDR3, but I think it's 1333; that's not enough to feed all 6 cores, so I agree that your "ideal" production is an overestimate. I don't run mprime on it, so I don't have my own numbers. Last fiddled with by VBCurtis on 20170520 at 01:24 
20170520, 01:20  #9  
∂^{2}ω=0
Sep 2002
República de California
11658_{10} Posts 
Thanks for the detailed cost analysis, David  tiny quibble, it should 'iterations per Watthour' (or any other power*time unit.)
Quote:


20170520, 01:49  #10 
Sep 2003
5×11×47 Posts 
CPU vs GPU? There's a third contender here... I can't resist a little cloud propaganda.
More precisely phrased, it's 2735.5 iterations per watthour, or 2.73 M iterations per kWh A more realistic estimate, as you noted, would multiply by a factor of (175.64 / 214.28) to account for slowdown when scaling up from using one core to using all six cores. So 2.24 M iter / kWh for a 5650@2.67GHz doing 4M FFT. Meanwhile, a c4.large cloud instance on AWS can do 45 iters/sec for 4M FFT, or 162000 iters per hour at spot prices of around $0.013 / hour (in useast2 region), or about 12.4 M iter / dollar. All electricity costs are already indirectly included in this hourly rate and are not separated out and billed to the customer. Unlike the 5650, this scales linearly when you increase the number of instances, because each instance will surely run on a different physical server (there are millions of servers in the cloud). Doing the math, this means that if your electricity costs more than 18 cents per kWh, you are better off running six c4.large instances in the cloud instead of that 5650, based on electricity costs alone. In practice, the comparison is even less favorable since you had to shell out $260 upfront to purchase the 5650, versus $0 upfront for the cloud. You'll also incur a small cost for additional air conditioning when running your own hardware. Of course, spot prices in AWS can fluctuate, but they've held fairly steady between 1.1 cents per hour and 1.3 cents per hour for more than three months now (can't look up historical price data beyond that). This is in the useast2 region, other AWS regions are pricier, sometimes much more. To be sure, 18 cents per kWh is well above the average for the US, but according to these government figures, electricity is more expensive than that in New England, California, Alaska, and Hawaii, and very close to that in New York state. And according to these other government figures (the chart is from here), electricity is more expensive than that in many European countries, including Belgium, Denmark, Germany, Ireland, Spain, Italy, Netherlands, Austria, Portugal, Sweden, and the UK (recall that 1 EUR = about $1.12 currently). In some cases much more, for instance Denmark at €0.29, or about 32 cents (US$), per kWh. VBCurtis's info in the lefthand side indicates a location of California, where power apparently costs 18.68 cents per kWh. If so, you'd be better off reselling that 5650 on eBay and getting whatever you can for it, and applying that money to running mprime in the cloud... maybe that's what the person who sold it to you did 
20170520, 02:00  #11  
"Forget I exist"
Jul 2009
Dumbassville
2^{6}·131 Posts 
or just these:
Quote:


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