Low hashrate after adding one more gpu to rig

Hello everybody. I have a strange issue, may be someone can help me.

I had a two stable linux rigs with asus motherboard and four r480 gpus in each rig.
But i have a 2 r480 gpus spare.

I replace one asus motherboard with MSI z170 gaming carbon with 7 pci-x slots. With 4 gpus everything is going well (each gpu get 280-290ss) but after i added a one more gpu to the rig my hashrate is very slow. At the begining 3 gpus runs well at 280ss and 1 has a only 60 and one 150.
After a half and hour only one gpu runs full speed, other 4 has only 60-70 ss. Very strange behaviour.

Tutorial on this forum about runing 7 gpus on MSI z170 gaming carbon didn`t helped me.

I encountered the same thing after I added a Powercolor RX480 8GB to my Sapphire HD7950 Vapor-X 3GB.

The HD7950 went from 280 sol/s to 240 sol/s while the RX480 is getting 300 sol/s.

Update: Realised that the GPU clock was reset back to 850MHz instead of the overclocked 1045MHz on my HD7950. The hashrate went back to normal after I used MSI AfterBurner to set the overclock. Temperatures are really high with 2 GPUs though, reaching almost 80C.

all my GPU are the same, sapphire rx480 4gb. And all 10 runs great in a different rigs. Only when i install 5 in one rig instead of 4, hashrate goes down. Core temperature is very low, its not a reason. And there is now any overclocking things, all params are stock (i dont know the way to overclock gpus on linux, may be someone knows).

same here with Linux

Windows 10 and updated mobo (1.7) solved all my problem.

MSI Z170A GAMING PRO CARBON with 4x gtx 1070 and 2x gtx 1080

I updated bios to last version but cant start 5 gpu in windows, only 4! On the MSI PRO CARBON. May be i need clean windows install and connect gpu one by one... What bios settings you are using to run 6 gpu?

Settings bios > Advanced > PCI subsystem Setting
PEG 0 and PEG 1 > Gen1
Above 4G Decoding > Enabled
that's all

Well. Today i was trying to start some gpus on my second rig on this mainboard and win 10. If i drop bios to default settings i can run 4 gpus. When i insert the 5th - i have a errors in windows device manager.
When i set bios settings PEG0, PEG1 and 4G i cant start rig at all. Black screen after POST information and in the integrated video output and on GPU video output.
May be its a riser fails and i have to buy a different ones?
Tomorrow will try to run rig with PEG0 and PEG1 right settings without a risers, just insert 1-3 GPUs into mobo...
8(

Is the card on a riser? If so, that's likely to be the problem.

i think so too. will try to start the rig without risers at all just to make a test.

I meant the riser the card is connected to is probably bad, just to be clear.

thanx to all you guys.
The problem was in chipset drivers. To make new rig with this card you need to following steps:
1) update mobo bios
2) drop it to default settings
3) install win 10 64but
4) install all chipset drivers and only after that
5) change advanced PCI settings in bios.
6) check if rig can be booted in windows.

If you change advanced PCI settigns in bios without installed chipset drivers your windows will never start again and drop in black screen after bios POST. Restring default bios params will not repair you OS, it will not start.
Tested on my 2 rigs with this mobos (gaming pro carbon).

Today i found the time and tested all variants of install. now all 2 my rigs runs with 5 r480 each. finally )

1 Like

Did you start all 7 gpus?

good question :slight_smile:

no, have only 10 GPUs for 2 mobos. The main problem was the black screen after enabling advanced PCI params in bios. Without it mobo can start only 4 gpu. Now i have 5 GPU rx480 in each rig. I cant install more because of power issue. I have 2 thermaltake 750w PS in each rig, but dont like it. Some of them are switched off itself from time to time ))) Or rig cant drop to BSOD because of low power i think )