Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!tektronix!tekig5!wayneck
From: wayneck@tekig5.PEN.TEK.COM (Wayne Knapp)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Virtual Memory / doable 1.4 request / Hot links
Message-ID: <4182@tekig5.PEN.TEK.COM>
Date: 15 May 89 18:24:18 GMT
References: <8905132203.AA27784@postgres.Berkeley.EDU> <17209@usc.edu>
Organization: Tektronix Inc., Beaverton, Or.
Lines: 50

In article <17209@usc.edu>, papa@pollux.usc.edu (Marco Papa) writes:
> One of the positive effects of the Apple propaganda of System 7.0 seems to
> have been the conclusion that Virtual Memory would be a very nice addition to
> AmigaDOS and it might not be TOO difficult to add to a future version of the 
> Amiga system software.  I am claiming that 1.4 SHOULD include support for VM.
> If possible, I would suggest that one of the V1.4 sessions at the June DevCon
> include a discussion on "VM & 1.4" (of course if Dave Haynie doesn't show up
> with VM-SetCPU :-) Andy? Lauren?
> 
> -- Marco Papa 'Doc'

Well I don't agree.  There is a much more basic problem that should be
addressed before virtual memory is added to the Amiga.  This is the
problem that there are two pools of different memory in the Amiga.  VM
(virtual memory) won't buy one much more than the ability to run multitasking
programs very slowly until you run out of CHIP RAM.  The real bottleneck
in the Amiga is the CHIP RAM.  It is limited in size, speed, and location.
So why not build a system like this:
                        
Amiga 3000         +===####################
----------         +   # Page control RAM #
                   +   #################### 
 ###########    #######    ######################               ####### 
 #  CUSTOM #====# MMU #====#                    #     #######   #     #
 #   CHIPS #    #######    # Single Pool of RAM #=====# MMU #===# CPU #
 ###########               #                    #     #######   #     # 
                           ######################               #######

Now you would have a system that VM could be added to.  Programming 
would be easier and maybe we would see some real improvement in the
Amiga.  The above changes may require some changes in the custom
chips, since some things like the VIEW are global, but maybe not.
If the system was smart enough it could use the MMU to map what ever
pages RAM needed into the custom chips address space.  This way one
could even have appications that used multiple megabytes of CHIP ram
even though at any one instance the custom chips can only address one
megabyte of RAM.  Some kind of MapToChips() function and a HoldToChips()
function would have to be written, but with today's hardware this 
shouldn't be too hard. 

Things like using the blitter to move memory anywhere to anywhere would
be possible.  Or using almost a whole megabyte of RAM for a graphics 
display and being able to page flip to another whole display would be
easy.  The mind would be the only limit on what could be done, since
making memory available to the custom chips would only require setting
up the MMU.   

Also the Amiga would be much easier to improve.  So what do you all think?

                                       Wayne Knapp