Yeah, I got the Cosmic 1000 in a lot buy. I was able to dump the lower 7 bits (using R15 instead of R10), but I couldn't get the high bits out. Then when I blow-torched it the plastic stuck on the die and I had to boil it in nitric acid to clean it up. I chipped a couple of edges, but got lucky and the ROM and PLAs were OK.

It's possible that the Cosmic 3000 TMS is a different revision and all 8 bits could be dumped.