Path: utzoo!dciem!nrcaer!julie!mcr
From: mcr@julie.UUCP (Michael Richardson)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Virtual Memory
Message-ID: <0520.AA0520@julie>
Date: 23 Feb 89 22:05:05 GMT
Article-I.D.: julie.0520.AA0520
References: <666@microsoft.UUCP>
Followup-To: comp.sys.amiga.tech
Distribution: world
Organization: Sandleman Software Works' Debugging Department, Ottawa, ON
Lines: 35

Bradford Christian writes:
>Is anyone out there in net-land with a 2500 (or some expansion card with
>an MMU) working on virtual memory?  The rom to ram thing sounds fun, but
  Thinking about it. I don't have 68020 on my Amiga to play with either.

>I think we should beat them with a public domain virtual memory handler
>for properly equipped Amigas.  I would be working on this right away,
  It would be nice...

>So, once again, is there anybody out there woking on something like this?
>Does anyone know of any problems one might encounter doing this?
  The biggest problem that will occur is that Exec/AmigaDOS/Intuition
seems to have these chains of pointers which tasks must access. What has
occured to me is that one might be able to have Virtual Memory in the address
space above 0xffffff (the highest 24 bit address) and leave the bottom
16meg that the standard 68000 can access unmapped.  I'd like to put user
stacks up there (where they can be expanded by page faults) and maybe
resident commands too. (Copy on write would get rid of the problem with
self modifying code and statically intialised variables.)

>Are supposed to access the mmu directly, or does C/A have some sort of
>software interface we should use?  Am I babbling?  Where did I learn
  I'd like to know that too. I suspect that standard 68020 MMU instructions
would work.

>        BradCh


--

  :!mcr!:
  Michael Richardson                     Amiga
                                  v--------+
 UUCP: uunet!attcan!lsuc!nrcaer!julie!mcr  | INTERNET mcr@doe.carleton.ca
 Fido: Michael Richardson @ 1:163/109.10<--+ Alter @ 7:483/109.10