On Thu, Jul 16, 2020 at 4:42 PM Josh Dersch via cctalk <cctalk@classiccmp.org> wrote: > On Thu, Jul 16, 2020 at 1:34 PM Josh Dersch <dersc...@gmail.com> wrote: > > Picked up a board advertised as a "4mb memory board" for a VAX-11/750... > > I think I may have answered my own question here; looks like it's for a VAX > 8000 series:
That makes more sense than a board that replaces the memory controller. IIRC, the 11/750 has an architectural limit of 14MB of RAM, but that might just be because of 8 memory slots (individual select lines), the implementation of the L0016 memory controller, and that's what you can hit with 2X 4MB boards + 6X 1MB boards. I _think_ if you could have gone to 16MB of RAM, DEC might have made a memory controller that could control 3X 4MB boards + 4x 1MB boards or 4X 4MB boards, but they did not. I installed the extra memory line wire on the backplane of our 2MB 11/750 (and installed the L0011), but we never made that final jump from L0011 -> L0016. By the time that was available, we weren't going to spend that kind of money on that machine. It still has 8MB to this day. -ethan