Best work choice for these machines

[paulunderwood]

Originally Posted by kruoli

If you would be going solely after that, you should fix your preferenced work type beforehand and select the processor after that. Yes, not what garo asked for.

I know. Taking electricity costs into account is a must. One could replace the components of some older boxen, Keeping the box, PSU, mains cable, graphics and disk, and replace the CPU, board and RAM. However if these are non-standard layouts such as some boxen from Dell etc it may present some problems attaching cables.

Once my 9100f is is set up, I can remove the cheap nvidia 710 and have ssh access only.

[garo]

Happy to take any and all suggestions. So fire away regardless of what I asked. So we got solar panels installed last year and on sunny days I end up exporting a good bit for free. So electricity is effectively free during the day from April to September.

I did a recce of the hardware in the house and this is what I have apart from a couple of old - like really old - laptops where it's not worth running anything:
1) Core2 6400 - Almost permanently off. Not worth running. Has a GTX580 and a good Corsair PSU that I may migrate to another computer but tbh at this point don't see this computer doing anything.The 580 is also plenty noisy and power hungry.
2) Core i3-2350M laptop - rarely on and will be used even less in the future. I've left two TFs on it to finish up and then NoMoreWork.
3) Core2 6600 - HTPC so is on for a few hours every day. I've now changed it to do DCs using both cores for a single worker moving a 79% complete DC to a faster machine.
4) Pentium E2200 on occasionally - 1 P-1/1 TF
5) Core i5-750 on most of the time: 3 DC/1 P-1 (Best candidate for an upgrade. New PSU, CPU, RAM, mobo and a Radeon VII)
6) Core i7-4770 on all the time: 3 DC/1 P-1 (Dell so non-upgradeable)
7) Core i5-7500U laptop - SO's main work machine. Not gonna risk it.
8) Core i7-8365U laptop so on sometimes - 1 DC on 4 cores.

PS: I priced a 9100F and yes it is a mouth-watering prospect. But as you can see from the list above I have so much old hardware lying around.

[Prime95]

Originally Posted by garo

Happy to take any and all suggestions.

The Radeon VII is so fast that it is the *only* upgrade worth considering. You will find it is more than 10 times faster than any quad core processor you are considering.

So, I'd recommend 1) Sell off as much of the existing hardware as you can. 2) Keep one non-laptop with a PCIE 3.0 slot. 3) Upgrade the power supply if needed to power a 250 watt card with two 8-pin connectors. 4) Buy a new or used Radeon VII. 5) Install Linux.
6) Optionally run something on the CPU, or pocket the energy savings for future purchases.

To get an idea of Radeon VII output. I have just started putting my GPUs into Summer power-saving mode (even though it is snowing right now :). A 5M FFT (exponents to about 97M) runs at 0.615ms / iteration using about 200 watts. In Winter mode, it is about 0.567ms / iteration at about 240 watts.

For comparison, my "dream machine" KabyLake quad core cpus are about 7.4 ms/iter. This is a setup optimized for minimal energy usage -- about 60 watts.

[garo]

Thanks for that George. Unfortunately I don't see myself getting any money for selling the existing hardware. But will buy a RadeonVII next. The Dell Mobo has PCIe 3.0 but the PSU is not any good with custom connectors etc. Might go the whole hog with a PSU, 9100F, mobo and RAM with a Radeon VII.

[Mark Rose]

Originally Posted by garo

@Mark Rose: That's a good suggestion. These machines are somewhat bandwidth limited with only DDR2-666/800. I assume using two cores for a single worker will more or less halve the iteration time?

That's the idea.

[garo]

Thanks. Maybe the really old stick two cores together without sharing cache - was Conroe doing this? - may not be twice as fast but hopefully the sandybridge laptop
will be close.

[garo]

So ran benchmarks across a number of a machines with different memory speeds and CPUs and this is what I am going with.

Core2 6600: 1 worker - there was almost no difference between 1 and 2 workers.
Nehalem - 4 workers - significantly better throughput.
Haswell - 1 worker on 4 non-hyperthreaded CPUs.
KabyLake/Coffee Lake laptops - 1 worker on 4 processors

[henryzz]

Originally Posted by garo

Core2 6600: 1 worker - there was almost no difference between 1 and 2 workers.

Probably due to memory bandwidth being the issue. Bet you don't get any meaningful improvement between 3 and 4 cores either.

[garo]

Its a dual core on DDR2 so yes memory bandwidth is a big issue. Didn;'t try with 3 or 4 workers obviously.

[henryzz]

Originally Posted by garo

Its a dual core on DDR2 so yes memory bandwidth is a big issue. Didn;'t try with 3 or 4 workers obviously.

Silly me. I assumed Q6600 not E6600. I seem to remember 1066mhz ddr2 being enough for 2 cores(and nearly 3).

[S485122]

Originally Posted by henryzz

Silly me. I assumed Q6600 not E6600. I seem to remember 1066mhz ddr2 being enough for 2 cores(and nearly 3).

And degrading over time : all my Q6x00 machines started to give errors in Prime95 after a few years. I have not had that problem with DDR3 or DDR4. If memory serves all memory speeds above 800 MHz (*) were overclocked and my experience is that they didn't stay stable over time.

Jacob