Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!UOTTAWA.BITNET!451061
From: 451061@UOTTAWA.BITNET (Valentin Pepelea)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Virtual Memory / doable 1.4 request
Message-ID: <8905180317.AA10448@jade.berkeley.edu>
Date: 18 May 89 02:52:58 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
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Darren New <new@udel.edu> in Message-ID <15706@louie.udel.EDU> writes:

> P.S., I always assumed MEMF_PUBLIC meant memory that would be shared between
> tasks, thus providing an upgrade for when memory mapping/protection is
> implemented (much like the MEMF_CHIP that most 1.1 programs failed to use).
> Are you saying that MEMF_PHYSICAL/MEMF_VIRTUAL is needed to lock pages in
> RAM or needed to allow sharing? -- Darren

Here is are the definitions of the flags as they are/will/should implemented:

MEMF_CHIP       The lower 512 or 1024 kilobytes of memory accessible by the
                graphic coprocessors.

MEMF_FAST       Memory not accessible by the custom chips.

MEMF_CLEAR      The memory gets cleared before it is allocated.

MEMF_PUBLIC     Guarantees that the memory returned is accessible for both
                read an write operations by all tasks. If not specified, the
                memory returned is accessible only for reading by other tasks.
                This flag is to be used when memory protection is implemented,
                and has nothing to do with virtual memory.

MEMF_PRIVATE    The memory returned will not be allowed to be read bor written
                to by other tasks. Useful only for multi-user systems.
                Hopefully will never be implemented on the Amiga. There are so
                neat tricks you are not allowed to do on multi-user systems.

MEMF_PHYSICAL   Or better yet, MEMF_LOCKED, guarantees that the memory returned
                will never be paged out of physical ram.

MEMF_VIRTUAL    Returns a block of memory that is probably going to be in
                the virtual memory addressing range. Hopefully you will never
                see this; intended as a compatibility feature to allow old
                and new software to coexist. Also provides CPM-80 compatibility
                under AmigaDOS.  :-) Timex-80 compatibility in the works.

Dave Haynie just reminded me the virtual machine capibility that an MMU
provides. Thus Forbid() and Disable() may turn out not to be a problem
after all.


Valentin
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"An  operating  system  without         Name:   Valentin Pepelea
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