Re: Virtual Memory on the Apple II

[cschroed@hercii.lasc.lockheed.com (Curt Schroeder)]

At the risk of this being vaporware, there has been enough discussion about
virtual memory on the Apple II that I can not keep silent.

I have prototyped a software virtual memory library that would allow an
_application_ to have a virtual dynamic memory space (i.e. a virtual heap).  I
have prototyped it under Apple CP/M using Turbo Pascal 3.0 and completed initial
testing.  The initial test results look promising, but I have not had time of
late to get back to the project and do my exhaustive testing of it (moving tends
to dissrupt one's projects :-/

The library provides paged virtual memory with a "manual transmission" interface
(as opposed to having a MMU, which would be an "automatic transmission" 
interface).  It is somewhat invisible to the programmer, but not totally (some 
care and discipline must be used).  Since this is being developed in an 8-bit, 
64K memory, CP/M environment, let me assure you that can address _more_ than 64K 
of virtual memory space.

I don't wish to divulge much more, because I plan to submit the Turbo Pascal
source and an article about it to "The Computer Journal," a small press journal 
that deals mostly with CP/M (and ZCPR) based and FORTH based applications.  After 
completion of the article for TCJ, I then plan to port the library to Hyper-C 
for use on the native Apple II hardware.  In both cases, the source will be 
made available as freeware.

I have cross-posted this to comp.os.cpm, since that is the OS where I am doing my
initial development.  All followups should go to comp.os.cpm (which I read every
weekday via the CPM-L mailing list).  Encourgement is welcome!

Curt

-- 

Curt Schroeder                        | cschroed@hercii.lasc.lockheed.com
Lockheed Aeronautical Systems Company | marylynn@netcom.com (1st prefered)
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These opinions are mine, mine, mine!  |    --- Apple II Forever! ---