How do you make them mine monero with 4 and something else with the other two?
A friend with 5 found a solution, that is working (at least for him). I am going to try it with the next restart.
After reboot - change virtual ram size. In his case he changed from 90 to 80. But I guess any change would do the trick. And then move sliders and confirm the HBCC size.
For me it worked with 5 once, when I upped the virtual ram from 64 to 80. That info I got from him have not tried yet, as I am very busy today, but will do with the next restart.
In any case, to make 6 work, it seems we need 96 or more virtual ram, and I simply don't have that much space on the SSD. Someone with bigger SSD should try it.
Isolate the two bads cards, launch Claymore with -di flag to only use those two cards.
You need ~8GB per card of virtual memory. Just launch xmr-stak-amd with 1 GPU and watch your virtual memory usage jump. It is linear with each card you add. Also the virtual memory only appears important when launching xmr-stak-amd. I will try messing with virtual memory settings and restarting my miner when I get a chance to see if that helps. With 4xVEGA 64 @ 1900H I need 32GB Virtual Memory. When I add the other two cards (that refuse HBCC settings) my virtual memory needs hit 48GB. So it appears all cards are indeed requested 8GB extra memory with our intensity settings however 2 of them are stuck at the low 'non-hbcc' hashrate of 1300H.
TLDR; I don't think we need 96GB of Virtual Mem. I believe it is 8GB per card.