On 2024-03-07 22:14, Paul Koning wrote:
On Mar 7, 2024, at 3:43 PM, Johnny Billquist <bqt%softjar.se@localhost> wrote: Physically, one could never get 128M in an 11/780. However, architecturally VAX supports up to 512M. So it shouldn't really be a problem.There's also the question of what the memory bus on each VAX implementation can handle. I forgot the 780 answer but chances are its address bus width is not nearly enough to support 512 MB.
True. Which is part of the "physically not possible". But I haven't looked at how many address lines go to the SBI. But it got to be a fair number anyway, and it also manages the space for the I/O part.
But for a simulator that's less of a problem anyway. And I know atleast with VMS on an emulated 8650, I can go all the way to 512M. But there I know that it's at least theoretically possible to do in real hardware as well. Just that with the memory cards that were available, the maximum possible was 260M.
But with simh, you just fake memory cards that don't actually exist in real life. Not a problem for the OS.
Johnny
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