system locks when running 5 gpus.

[logicminds]

version 0.6.1
linux: Ubuntu 18.04.3 LTS
driver: amd-gpupro 18.40
Mix of Vega 56 and 64
Samsung memory

When starting the miner it crashes during the dag generation and locks of the system completely.GPU 0 Starting DAG generation for epoch 303.

This seems to only happen when I use greater than 4 gpus. I can get the miner to work with 4 GPUS using the -d option.

[setuidroot]

What is your hardware setup exactly? I mean motherboard type, CPU type, RAM amount, HDD or SSD and its size. More specific information on the GPUs would also be helpful... I assume they're all 8GB cards? What do you have your GPU cards clocked at (core clock/voltage, memory clock/voltage and memory timings?) Have you tried switching cards and/or GPU risers around?

My best guess (without more information) is that your motherboard doesn't like more than 4 GPUs. This wouldn't be the first motherboard limitation on the number of GPUs. Things to try:

1: Go into BIOS and look for an option dealing with "4G encoding" try toggling that BIOS option (if you have the option) and reboot, see if that helps at all.

2: If you have an integrated GPU (iGPU, usually built into the CPU chip with newer CPUs) then try disabling the iGPU in the BIOS and use the first GPU card (GPU 0) for video feed. I've read with ETH sometimes you must plug in a monitor (or a dummy plug) into "GPU 0" or you'll experience similar errors.

3: Try setting PCIe to "Gen 2" in the BIOS.

4: Try exporting the environmental variable "export GPU_MAX_ALLOC_PERCENT=95" (it's usually set equal to 100, try it at 95; source: https://forum.ethereum.org/discussion/2493/try-out-the-new-go-gpu-miner-just-geth)

5: Make sure you have enough system RAM (and swap) to run more than 4 GPU cards. 16GB of RAM would be good and they usually recommend double your RAM in swap. This might be your problem because if your system doesn't have enough swap space then it's commom for ETH mining to crash with DAG errors. Since you're on Ubuntu 18.04 you'll have a swapfile (as opposed to the older swap partitions.) If you don't have a swapfile, you can create one easily...

Check for swap:

sudo swapon -s

This will show you the current size of your swapfile (default is 2GB I believe.) If it doesn't show you anything, then you don't have an active swapfile at all.

I'll assume you have the default 2GB swapfile, here's how to resize it to 16GB:

sudo swapoff /swapfile

sudo dd if=/dev/zero of=/swapfile bs=1M count=16384

sudo mkswap /swapfile && sudo chmod 600 /swapfile && sudo swapon /swapfile
 

To make this persistent across reboots, you may have to add the /swapfile to /etc/fstab, like so:

sudo echo "/swapfile none swap defaults 0 0" >> /etc/fstab

If you already had a /swapfile (and you used the same file name) then there's a good chance /etc/fstab already has an entry to load the swapfile. You can check first:

sudo nano /etc/fstab

If it does have an entry already, you might have to modify the string to match the one I suggested above in the echo command. But this is just a basic recommendation, you should do your own research first. Just know that for ETH, you do need a swapfile (and a large enough one at that.) 16GB should be sufficiently large for most GPU mining rigs. Make sure you have enough storage space for that large of a swapfile though. Also hopefully your Ubuntu is installed to a HDD/SSD disk and not a USB stick. USB sticks don't have the read/write transfer speeds to host a proper swapfile.