You using Win10? Which driver you are using. You can't just calculate 2x3.75.
Can you mine ETH with clkernel3? If so, then you have not enough vram for ETC and clkernel3. What driver your using.
Yes i am using Win10x64 LTSC version with "latest" 20.4.2 driver.
And yes i know that Win is using my vram if there is a display connected to it.
I am mining with my PC 1x580 8GB without iGPU and i have one rig#1 with 4x480 8GB with iGPU and a mixed rig#2 with 1x580 8GB 5x470 4GB with a iGPU
Yesterday the #1 4x480 8GB gave me problems with clkernel3 and the fix was switching to clkernel1.
Everything was fine until ETC epoch 347-348.
Simple logic if 4gb cards work clkernel1 then 8gb cards should work clkernel3 or am i wrong?
Tested on my computer (32GB RAM) with 8GB RX570, driver 19.9.1 and epoch 353. clkernel 3 works but the hashrate falls from 28.4MH/S (with clkernel 1) to 21 MH/S (with clkernel 3). I suppose you don't have enough physical or virtual memory but even if you had it you won't like the -7 MH/s fall. The problem is in the driver. It takes shared memory from your computer and the transfer with this memory leads to this -7MH/s fall (if your GPU ise not on PCI-E X 16 this fall will be at least -28 MH/S). So you can't use clkernel 3 because of the driver. There is enough VRAM for 2 X DAGs (2 X 3.77 GB for epoch 353) used from clkernel 3 but the driver decides to use your computer memory. There is no way to tell it not to do it. If you check all the drivers from 18.1.1 to 20.5.1 maybe (maybe not) you will find a driver that doesn't allocates host (computer) memory, but the chances are very small.