Does CPU matter when mining?

[davemanet]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

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[DarrenJC]

Nope, it'll be your OS not liking more than 7 cards from a single brand? Nvidia or AMD...

[davemanet]

Weird I'm using simplemining which is linux, usually people report 8 cards working fine on here

[Mattthev]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

Not really, cheapest Celeron is fine. Only maybe if you run 10 or more NVIDIA cards some miners need better CPU. AMD miners need a lot less CPU power. But top CPU you might need is some cheap Pentium with HT

[leowonderful]

More likely the BIOS or OS itself not liking what's happening. Dual-core processors can handle 8 just fine, Intel or AMD. AMD quad core Phenom processors can be found quite cheap, and for newer sockets the G3930 is around $40, and the new Athlon X4 950 has 4 (Excavator?) cores on a budget.

[rdluffy]

I prefer to use a good cpu to have a better stability, for me is better

[UnknownX]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

I most of the cases it's OS or bios issues, so try to update your bios first.
But CPU also have big value to rig stability, so it's better not to buy the cheapest one, try something middle priced if you built new rig.

[DrG]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

I most of the cases it's OS or bios issues, so try to update your bios first.
But CPU also have big value to rig stability, so it's better not to buy the cheapest one, try something middle priced if you built new rig.

Short of going for a single core ancient Pentium, the money would be better spent on a higher end power supply. Better ripple control and consistent power keeps cards mining reliably.

[UnknownX]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

I most of the cases it's OS or bios issues, so try to update your bios first.
But CPU also have big value to rig stability, so it's better not to buy the cheapest one, try something middle priced if you built new rig.

Short of going for a single core ancient Pentium, the money would be better spent on a higher end power supply. Better ripple control and consistent power keeps cards mining reliably.

I think nobody will argue that high end power supply is musthave for good rig, but also it is obvious that building rig at 1080ti with cheap CPU is also very silly idea, it's better to spend additional 20-30 usd to buy normal CPU to get stable hashrate and not to receive CPU errors or miner's crashes every few hours.

[davemanet]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

I most of the cases it's OS or bios issues, so try to update your bios first.
But CPU also have big value to rig stability, so it's better not to buy the cheapest one, try something middle priced if you built new rig.

Short of going for a single core ancient Pentium, the money would be better spent on a higher end power supply. Better ripple control and consistent power keeps cards mining reliably.

I think nobody will argue that high end power supply is musthave for good rig, but also it is obvious that building rig at 1080ti with cheap CPU is also very silly idea, it's better to spend additional 20-30 usd to buy normal CPU to get stable hashrate and not to receive CPU errors or miner's crashes every few hours.

Thanks so the cpu can be a cause of unprecitable behaviour? I went with the cheapest g3900 she just couldn't understand why i got it working with 7 but when i put in the 8th it acted up. I'm going to order a g4400 now. I'm using Evga g2 so i don't think it's the psu.

[DrG]

I have 7gpu rig that works.  When I put in an 8th gpu, all the other cards start to act up.  Could it be the CPU?

I most of the cases it's OS or bios issues, so try to update your bios first.
But CPU also have big value to rig stability, so it's better not to buy the cheapest one, try something middle priced if you built new rig.

Short of going for a single core ancient Pentium, the money would be better spent on a higher end power supply. Better ripple control and consistent power keeps cards mining reliably.

I think nobody will argue that high end power supply is musthave for good rig, but also it is obvious that building rig at 1080ti with cheap CPU is also very silly idea, it's better to spend additional 20-30 usd to buy normal CPU to get stable hashrate and not to receive CPU errors or miner's crashes every few hours.

Thanks so the cpu can be a cause of unprecitable behaviour? I went with the cheapest g3900 she just couldn't understand why i got it working with 7 but when i put in the 8th it acted up. I'm going to order a g4400 now. I'm using Evga g2 so i don't think it's the psu.

Unless somebody is willing to give exact models of mobo and cpu having issues I call BS. I've used everything from a Sempron 140 to a I7-2600K for GPU mining since 2011. The only time I did see any bottleneck was when I used the Sempron because it was single core and creation of DAG is CPU instensive. When you use single core CPUs any operations other than mining (like a Teamviewer connection) does slow down hashrate.  I have frequently swapped back and forth between Celeron 530 and I5-3470 and not had any difference in share submission rate with Bitcoin, Monero, or Ethash (yes I mined Bitcoin back i the day). The caveat being I was not CPU mining as well.

If you plan on CPU mining as well it makes sense to go with an I5 or I7 or Ryzen equivalent. Just make sure you leave a core free to handle the OS and share submission for the miner.

CPU choice does effect the system memory speed utilized and could possibly alter the PCIe lanes if the board manufacturer does something wonky so there's always that, but a Celeron 3930 should be more than sufficient for a 8 card rig that's only GPU mining. You might see a small boost going from HD to SSD since disk i/o does slow down mining especially if running on low memory. Unfortunately DDR4 and flash memory prices are double what they were last year.

[Johny101010]

The CPU does not matter much. The PSU on the other hand does. I'd check the power draw if I was you.

[davemanet]

My power draw is within 80% of the psu's limits.  Is it possible that it's the bios on the GPU?  What's odd is that the cards work fine mining on their own but get weird when pairing with other cards.

[Johny101010]

What type of PSU do you have.

[jyakulis]

Yes it can matter with higher #'s of GPUs. I think it's something with the cache.

I could only get 2/4 1070's to run in windows with a sempron processor. I put a FX 6 core in and everything magically worked.

I'd spend an extra 50-100 bucks for a processor if I was doing a high GPU build personally.

[davemanet]

What type of PSU do you have.

EVGA G2.

I'm using a GPU bios that i found online.  I'm going to try reverting to stock bios for all 8 GPU's, this is going to take a while but I guess it's the only option I have left.

[Johny101010]

I'd hold of on doing all that. If you have 8gpu x 150 each is much higher than your 1200 PSU.
It is not your CPU your the bios it is more than likely the PSU.
Try to turn on the computer with 8 cards and just do normal stuff, not mining. It shouldn't act wired, once you start mining the rig will either drop hash like s rock, freeze or reboot.

[fanatic26]

All the people saying the CPU could be to blame are just plain wrong and dont understand how PC architecture works. Even on my 12 card rigs the G3930 Celeron is only at 25-30% usage at max. Could you be a bit more concise in your problem description? Cards 'acting up' could be anything. If you give some specifics it would help the troubleshooting process quite a bit.

[davemanet]

All the people saying the CPU could be to blame are just plain wrong and dont understand how PC architecture works. Even on my 12 card rigs the G3930 Celeron is only at 25-30% usage at max. Could you be a bit more concise in your problem description? Cards 'acting up' could be anything. If you give some specifics it would help the troubleshooting process quite a bit.

Ok this makes me realize that it's not the CPU at fault, thank you.

If the GPU is stable on it's own, that means it should be stable in a rig.  Is that correct?

The problem I'm having is that I tested gpu's and it's fine, but then when I add more I get odd behaviour, for example some cards going from 28 to 14 hash, and inbetween.

I think I've narrowed it down to the fact that when I add more GPU's, the usb cables get angled to fit into the position of my rig.  So, bent usb cables = abnormal behaviour.  Is this possible?  I'm testing it now.

[DrG]

First thing is to identify what motherboard is being used. The OP PMed me and said the addition of the 8th card causes variation of rate from 28 to 14 and back. Knowing the motherboard and bios revision would help.

Make sure to have virtual memory high enough. I would do at least 24576 for 6 card, some multiple of 4096 thereafter if using 8 like 8 x 4096.

The Power supply make be adequate, but if not cabled properly to the risers that can be an issue as well. Make sure no more than 2 cards per Molex or Sata chain. Splitting a 6 or pin cable is usually safer than using those two thinner cables.

Opening up task manager will usually help prove CPU is not pegged at 100% on a core or something is not stuck in the background. Using Afterburner helps show if the GPU core clocks are throttling and why they might be throttling.

Most important is to know the mobo model though.... else we're all just guessing.