CPU sweetspot

[poby]

I know the conventional wisdom is that the CPU is just gonna be idling most of the time and won't make an iota of difference to hashrates and yet...

I'm building a rig with a z270, starting off with 6 1070s and later maybe adding a couple more, so have got a corsair AX1500i to power it all.  I'm gonna be running windows 10 pro and somehow the idea of having all this nifty gear together with a bottom end G3930 celeron doesn't site right.  I've decided to go with a G4620 Pentium more for emotional than rational reasons I suspect.  I know the cpu isn't involved in the mining process but it does do all the other OS housekeeping stuff, which might have an effect?

Is there anyone running windows 10 with a 6 to 8 GPU rig, and a celeron CPU?  Is the extra I'm paying for a step up from a celeron a total waste money as far as a mining rig goes?

[Elder III]

If you just have it sitting there mining one algo on all the GPUs and don't ever do anything else with the system a Celeron is fine. We have a couple of 3920s as well as a couple older gen dual cores in mining rigs.  The catch is that the if you want/need to multi-task at all you're pretty much screwed if you do much more then open a web browser. Normally that's not an issue, but we did run into the problem of having a mixed GPU system that we wanted to have automatically start mining 2 different algorithms after Windows starts up in case of a system reboot, power outage, etc... having 2 different miners start at the same time would hang the system and be frozen due to maxing out the CPU. Our next several builds are going to be Ryzen 1600s so that will most definitely not be an issue there, plus they are good CPU miners to pay for the extra cost very quickly.

[poby]

If you just have it sitting there mining one algo on all the GPUs and don't ever do anything else with the system a Celeron is fine. We have a couple of 3920s as well as a couple older gen dual cores in mining rigs.  The catch is that the if you want/need to multi-task at all you're pretty much screwed if you do much more then open a web browser. Normally that's not an issue, but we did run into the problem of having a mixed GPU system that we wanted to have automatically start mining 2 different algorithms after Windows starts up in case of a system reboot, power outage, etc... having 2 different miners start at the same time would hang the system and be frozen due to maxing out the CPU. Our next several builds are going to be Ryzen 1600s so that will most definitely not be an issue there, plus they are good CPU miners to pay for the extra cost very quickly.

I wish the forum software allowed "likes" or "thanks" because I really appreciate your input.  It's food for thought and exactly the kind of real world info I'm looking for.  Based on your experiences, I feel a little better with going with the pentium.  The rig is purely for mining but I might mine more than one algo or at least I want the option to do so without it causing problems.

[Elder III]

I should have mentioned that we also have one rig with a Haswell era i3 CPU and it does not have the issues with multi tasking that the Celeron CPUs do. If I had to do it over again for all the Celeron based rigs I'd probably spend the extra for a Pentium, esp if it was a newer model with HT enabled.

[jpouza]

I know the conventional wisdom is that the CPU is just gonna be idling most of the time and won't make an iota of difference to hashrates and yet...

I'm building a rig with a z270, starting off with 6 1070s and later maybe adding a couple more, so have got a corsair AX1500i to power it all.  I'm gonna be running windows 10 pro and somehow the idea of having all this nifty gear together with a bottom end G3930 celeron doesn't site right.  I've decided to go with a G4620 Pentium more for emotional than rational reasons I suspect.  I know the cpu isn't involved in the mining process but it does do all the other OS housekeeping stuff, which might have an effect?

Is there anyone running windows 10 with a 6 to 8 GPU rig, and a celeron CPU?  Is the extra I'm paying for a step up from a celeron a total waste money as far as a mining rig goes?

I know the feeling, I've started my rig in 2014 with a Pentium G CPU and 6 x 750Ti...nice CPU to go with mining rig, low TDP etc, but I also used that PC with normal tasks, so the CPU was a bottleneck and in the end I grab a i7 4770k at that time.

If you intend to let the rig just mining, the lowest CPU is fine, but if you intend to use the PC with other tasks, I strong recommend a better CPU.

[joblo]

If you just have it sitting there mining one algo on all the GPUs and don't ever do anything else with the system a Celeron is fine. We have a couple of 3920s as well as a couple older gen dual cores in mining rigs.  The catch is that the if you want/need to multi-task at all you're pretty much screwed if you do much more then open a web browser. Normally that's not an issue, but we did run into the problem of having a mixed GPU system that we wanted to have automatically start mining 2 different algorithms after Windows starts up in case of a system reboot, power outage, etc... having 2 different miners start at the same time would hang the system and be frozen due to maxing out the CPU. Our next several builds are going to be Ryzen 1600s so that will most definitely not be an issue there, plus they are good CPU miners to pay for the extra cost very quickly.

I wish the forum software allowed "likes" or "thanks" because I really appreciate your input.  It's food for thought and exactly the kind of real world info I'm looking for.  Based on your experiences, I feel a little better with going with the pentium.  The rig is purely for mining but I might mine more than one algo or at least I want the option to do so without it causing problems.

That's what the BTC address in his sig is for.

The key CPU feature for GPU mining is the number of threads it can run simultaneously. Clock speed is mostly irrelevant.
Each GPU card has a corresponding CPU thread so more CPU cores provides better thread distribution and less latency.
Latency occurs when a process must wait for an available core to run because all cores are busy.
More cores become more important of you intend to do anything else on that system.

If you want a minimalist system a Celeron is fine, otherwise jump to a CPU with more threads.

[Elder III]

Joblo is the man when you need details about CPUs ^^^ he's got one of the better CPU Miners out there imo.  

[Rockett0]

Really unscientific here but I anecdotally.

System 1.  z270 with Celeron
System 2.  z170 with I5

Both have identical RX 580's. MB are different brands, I'm sure bios settings could be way different, etc. But. . .


System 2 always finds more shares than system 1. Not at any order of magnitude, just more.

I suppose I could swap the processors from one board to another.

[poby]

The key CPU feature for GPU mining is the number of threads it can run simultaneously. Clock speed is mostly irrelevant.
Each GPU card has a corresponding CPU thread so more CPU cores provides better thread distribution and less latency.
Latency occurs when a process must wait for an available core to run because all cores are busy.
More cores become more important of you intend to do anything else on that system.

If you want a minimalist system a Celeron is fine, otherwise jump to a CPU with more threads.

I assume on a dedicated 8 GPU mining rig not doing anything else, the difference between a quad core with 8 threads and a dual core with 4 threads would be in the cents per day?

I won't be using it for anything else but I'm more comfortable with a little extra headroom just in case so I'm thinking a G4620 Pentium will do fine.  But then I have wondered if it would be worthwhile getting an i7-7700 (non k).  This would only be viable if I could make enough from CPU mining.  From what I can see from various online calculators, the i7 mining monero at best would make close to $1 a day.  So almost a year to pay for the extra i7 expense compared to the pentium, not considering likely increase in difficulty.

Also, I suspect if the cpu was busy mining, it might have a latency effect on the GPU mining, possibly enough to negate the extra buck a day.

Am I right in my assumptions? 

[grape_tectonics]

You underestimate how little anything other than the GPU's really mean. One of my rigs is a decade old pentium 4 with pci-e 1.0 and it hashes just as good as my desktop with a 5930k. The only time it goes over 5% load is when remoting in with teamviewer which almost kills it 

[KougarLOB]

Mining a bit of BURST from a CPU is easy.  Anyone who is running a GPU rig without also mining BURST is leaving money on the table.
I recently re-built a rig now using a Z170 board and Pentium G4620.  I wish I had spent another $20 for an i3 7300 or 7320.  Pentiums do not have AVX and AVX2, which is faster than SSE when processing BURST deadlines.  Would be noticeable on larger farms of 40+TB.  I was going to move my 75TB farm to that rig but will keep it on an X58 Xeon rig for now.

[KougarLOB]

Someone with a history of GPU mining private messaged me asking about recommendations for BURST mining.  Below is my reply as others may find it useful.

-----------

Q: ...I want to ask you something about mining, in the past I use to have rigs for LTC mining (on the good times ;-) And now I have the idea to start mining again using GPU ether or ZEC and Burst using HDD.
I have seen that you were able to mine GPU (Ether or ZEC) and HDD (Burst) at the same time using the same rig.
Can you give me an idea of what kind of rig are you using or what can I build to do that?

A: Any combination will work.  You are aware of what does into a good GPU rig - there's a half-dozen threads about exactly that at the top of the alt-mining forum.  Next step is to shove as many hard drives into that rig as possible.  Open air frames will require a cage of some sort to protect the drives their PCBs.  Start with spare drives you already have.  If you want more consider used 4TB or larger drives.  Open PCI-E slots on the motherboard can be used to add additional SATA ports via expansion cards.

GPUs can read back plots faster than CPUs but it's more profitable to have the video cards running ETH/DCR or ZEC.  The under-utilized CPU can write and read the plots quickly enough unless you are running a 100+TB farm.  My farm is about 75TB.

My main BURST rig has two video cards and 16 hard drives jammed inside a full tower case.  I installed a two cages that convert three 5.25" bays into five 3.5" slots with a fan.  Board had 6 SATA ports and two SAS ports (running SATA).  Also have three PCI-to-SATA expansion cards.  In the end I have two RX-480s and 16 hard drives (~75TB) shoehorned into a single steel shell and powered by an EVGA 1000W Titanium PSU.  Not a lot of hand room, mind you, with all the cables.  And heavy as heck.  Just moved it to our new house and mothersucker must weigh at least 70LBs.  Had enough room between the motherboard and PSU to mount a riser on the back wall and utilize the normal expansion slot openings in the case.

3x 5.25" to 5x 3.5" bay cage
https://www.amazon.com/gp/product/B0094KUAY8

Example of PCI-E to SATA
https://www.amazon.com/IO-Crest-Controller-Non-Raid-SI-PEX40064/dp/B00AZ9T3OU

Rosewill full-tower case
http://www.ebay.com/itm/Rosewill-Thor-V2-Gaming-ATX-Full-Tower-Computer-Case-Black-/262306052899
(Used one listed for $70 OBO)

[klondike_bar]

a celeron can handle a miner with identical cards (eg all 480s), but is under more load if mixing algorithms (such as zcash on 3xx cards simultaneous to eth on 4xx cards) and shows a bit of delay. works fine, but you might consider $20 more for an i3 on mixed rigs

[Elder III]

a celeron can handle a miner with identical cards (eg all 480s), but is under more load if mixing algorithms (such as zcash on 3xx cards simultaneous to eth on 4xx cards) and shows a bit of delay. works fine, but you might consider $20 more for an i3 on mixed rigs

Yep, this is what we found with our mining rigs as well. If all the GPUs mine the same algorithm in the same miner it seems to work pretty well... try to mix anything up between different GPUs and it's more laggy then I can tolerate personally.

[poby]

a celeron can handle a miner with identical cards (eg all 480s), but is under more load if mixing algorithms (such as zcash on 3xx cards simultaneous to eth on 4xx cards) and shows a bit of delay. works fine, but you might consider $20 more for an i3 on mixed rigs

Very good to know.  I feel good about going with the pentium (G4620).  Incidentally the performance difference between the kaby lake pentium and the kaby lake i3 is negligable.  Both are dual core with 4 threads.  The main difference seems to be the i3 has the avx extensions, which won't make the slightest bit of difference if I'm not cpu mining.

[posternat]

a celeron can handle a miner with identical cards (eg all 480s), but is under more load if mixing algorithms (such as zcash on 3xx cards simultaneous to eth on 4xx cards) and shows a bit of delay. works fine, but you might consider $20 more for an i3 on mixed rigs

Very good to know.  I feel good about going with the pentium (G4620).  Incidentally the performance difference between the kaby lake pentium and the kaby lake i3 is negligable.  Both are dual core with 4 threads.  The main difference seems to be the i3 has the avx extensions, which won't make the slightest bit of difference if I'm not cpu mining.

The only difference points would be a hugely mis-built system.  The data does have to travel through the CPU RAM and could bottleneck some if the numbers would ridiculous.  A mid-range 32 GB GPU card, flowing into a PC with 1 GB of RAM might see the data slow some upon entering the FSB.

[virasog]

a celeron can handle a miner with identical cards (eg all 480s), but is under more load if mixing algorithms (such as zcash on 3xx cards simultaneous to eth on 4xx cards) and shows a bit of delay. works fine, but you might consider $20 more for an i3 on mixed rigs

Very good to know.  I feel good about going with the pentium (G4620).  Incidentally the performance difference between the kaby lake pentium and the kaby lake i3 is negligable.  Both are dual core with 4 threads.  The main difference seems to be the i3 has the avx extensions, which won't make the slightest bit of difference if I'm not cpu mining.

The only difference points would be a hugely mis-built system.  The data does have to travel through the CPU RAM and could bottleneck some if the numbers would ridiculous.  A mid-range 32 GB GPU card, flowing into a PC with 1 GB of RAM might see the data slow some upon entering the FSB.

User built systems might get this jacked up, but the big culprit are the PC companies flooding places like Wal-mart with PC's that are widely different and built off a small base of motherboards.
This might put a system on the sales floor with lower PC specs, but nothing stopping a user from dropping two video cards in the box.  Too many generic stock boards used to built a wide set of spec'd PC's.