PDP 11 RL11/01 Address confusion.
ard at p850ug1.demon.co.uk
Tue Apr 1 14:23:14 CDT 2008
> I have used an RL11 in my 11/24 w/KT24 (to load real 2BSD from real magtape),
> so I'm pretty sure it works fine in a 22-bit environment (but I can't say
> if the KT24 just smooths over DMA buffer address issues or what). Dunno if
I believe that's exactly what the KT24 does. The F11 chipset (used on the
11/24 CPU board) has a full 22 bit MMU which addresses the 4Mbytes of
memory, but of course the Unibus only has 18 address lines, so DMA
addresses from peripherals (like the RL11) are only 18 bits wide. The
KT24 is the 'Unibus Map' -- a little MMU to extend those DMA addresses to
> you can stuff an RL11 in an 11/70 or not, but I would hope so (since there
> really aren't any Unibus peripherals that "know" about 22 bits).
AFAIk the 11/70 has a Unibus Map as part of the CPU. The 11/44 certainly
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