6 Nov
2012
6 Nov
'12
9:34 a.m.
On Tue, Nov 6, 2012 at 12:18 PM, Allison <ajp166 at verizon.net> wrote:
On 11/06/2012 10:53 AM, Ethan Dicks wrote:
OK. That's what I thought from my limited understanding of CP/M, but
I do appreciate the well-educated response.
...what CP/M software is out
there (except maybe a RAM disk) that can *use* 1MB?
Essentially none at the applcation level. It does make a super fast ramdisk though. For aps
that did overlays
like multiplan or multipass assemblers or compilers that is a huge speedup.
Sure. I've done that with a KT8A, 128K and a PDP-8... Lots of
address-constrained systems have benefited from falling RAM prices by
loading up 4x (or more) on the amount of RAM that user programs can
see but that is still usable behind system calls/device driver access.
...Things like tassk switching are possible
Makes sense especially if you might want to, say, keep an editor
session alive and switch over to something else (like a compiler) and
back.
The Z180 MMU is near identical to the PDP11
MMU save for the bits for page protection and memory exception traps.
Interesting. I had no idea. I've done some very minor fiddling with
the PDP-11 MMU under RT-11 (IIRC it involved some odd mapping twiddles
with a 512x512 framebuffer card and a scatter-gather DMA engine).
At the extreme there is Uziunix that uses 32K of ram
and maps applications
to 32k pages up to whats available. Since unix (even uzi) is a multitasking
system tasks loaded in remote pages get their timeslice and can communicate
with other tasks or applications.
Sure. I get how someone might use 1MB on an 8-bitter with a
pre-emptive multitasking system, but that's not what I think of when I
think of CP/M 2.2 on a Z-80.
In short anything a PDP-11 with MMU can do. (its a
16bit address machine
too).
If one is developing code, I do see numerous possibilities. I was
more curious about being strictly a user and soaking up that much RAM
outside of turning it into a RAM disk. It's not that I would never
develop any code on CP/M, but it's far more likely I'd be grabbing
stuff off the Walnut Creek CD-ROM or downloading things to run on it.
Thanks for the excellent reply.
-ethan