Im not saying you're wrong about the retina, but i picked one up on a lark, as my ZZ9000 won't play nice with either A3000D or A4000D - as they don't have a superbuster rev 11 doing full glitch free DMA.
That's my understanding from "Dr Chris Edwards" and he understands a lot. (LinuxJedi has a ZZ running fine w/rev 9 but he's a Jedi master
My big boxes have rev 7 and rev 9 respectively and im about to get a rev 11.
Amiga RTG really is hard to do easily. I'm also going to try out the new PicII clone, probably- on the A4K
The ZZ was great on the A3K - when it worked, usually less than an hour before freezing up every time - and my A3000 works great now without it.
But it has amazing dynamic range, ethernet, and usb so it is a pricey but full featured 21st century card.
Just wish Dave Haynie had the time/resources to get SB up to speed on all models, but he did amazing considering he was a 1 man ZII/III designer band!
