Ok then case closed . . .

Click to expand...

Case re-opened! From the bottom side. }

Continue discussion here if you would: Memory Addressing Questions

I'm already hip deep into the memory addressing issues of the IIsi, so I may as well head toward the deeper end of the pool and take on the Quadras 605 & 630 while I'm at it.

Yeah jt the q605/475 boots and runs great with the 4 Meg's on board removed.
Iisi works with onboard ram gone too, just on board video stops , works fine with video card.

Click to expand...

Great news, it turns out that only the Data lines are buffered by the 74LS245 quartet in order to buffer the Vampire VRAM/DRAM in Bank A.

We're getting there . . .