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From: ericmcg@pnet91.UUCP (Eric Mcgillicuddy)
Newsgroups: comp.sys.apple2
Subject: ViM
Message-ID: <9010040400.aa06851@generic.UUCP>
Date: 4 Oct 90 03:53:21 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 35

System 5.0 added the Out of Memory Queue to the system structure. Whenever you
ask for a block of memory there is a chance that memory will be compacted and
purgable blocks get purged. In lieu of this I propose that the blocks be
swapped out until sufficient memory is available. Also because of this,
unless you lock the block, a deferenced block may not be where you think it
is. CheckHandle will force the swap in of a memory block if not present in
real memory. This makes sense since memory pointers are no longer guaranteed,
unless one never allocates new handles (or reuses the same ones over and
over). Various other memory manager calls will force a swapin (don't have the
list in front of me). Vim will be exactly 64k in size and this includes an LRU
queue to track the oldest handles (it is fixed in size and limited to about
1000 memory blocks). Another option would be to alter the memory manager data
structure to include the LRU, but this is guarantted to break many programs
that don't exactly follow Apple's guidelines, and would also give DTS
kniptions. There is a possibility that ViM will work with 68000 based Macs,
but I think there is a good chance that the Mac's stack could be swapped (this
is bad), Bank 0 on the GS is inviolate to ViM (I'll code it in now! :).

Even if this is not 'true' virtual memory, it will at least provide automatice
overlays for huge programs. (Who'd ever need more than 1 Meg of memory
anyway:). additionally, this is only part 1 of a proposed 3 part series. Part
2 is Multi8, interupt driven task switching of 8-bit programs (prodos only at
this time, unlike Softswitch). PArt 3 is Vigour, true multitasking of 16-bit
programs. 

I am still not satisfied with what I've done so far, but I hope to release it
locally for Beta in the next 2 or 3 weeks. Dpending on how things go, I'll see
about getting it on the net by Christmas (Of what year you ask?). 

Also depending on how things go, I will likely be the owner of a 386 clone or
a ROM04 GS, whichever comes first, by Christmas. Not much point in time
slicing 2.8MHz is there? :(

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