Perhaps you had a Buster 9 or 11 in your other A3000. 7 doesn't do DMA. Also, does the HC+ have RAM on it like the A2091 cards are capable of?
Zorro II DMA works with all Super Buster revs. Zorro III DMA is the issue, but doesn't count here.
If the GVP uses DMA it'll make a big difference whether expansion RAM is present on it and how the buffer mask is set on the partition (Z2 DMA won't work with 32 bit RAM, so would go to chip RAM otherwise).
