Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!apple!oliveb!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga
Subject: Re: fastmemfirst
Summary: C00000 memory is not fast and not chip ram
Message-ID: <477@tardis.Tymnet.COM>
Date: 1 Aug 89 23:47:57 GMT
References: <11353@mcdphx.phx.mcd.mot.com>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: McDonnell Douglas Field Service Co, San Jose CA
Lines: 39

In article <11353@mcdphx.phx.mcd.mot.com> stan@teroach.phx.mcd.mot.com (Stan Fisher) writes:
>   When using the Super Agnes chip, therefore elimating the C00000 RAM,
>it is no longer necessary to run fastmemfirst in the startup-sequence, in
>order to conserve Chip RAM.  Was I dreaming this?   Was it the Super Agnes
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
          ^^^^^^^^ -- This assumption is false.
>alone that changed this? or was it the use of SetCPU 1.5 too?  Seems to me
>irregardless of Super/old Agnes, a program requesting "either type of RAM"
>could be given chip, when fast is available.

A plain A2000 with a 2 megs of expansion RAM has 3 types of memory:
  512K of chip RAM, which is slow due to access by the custom chips.
  512K of non-chip RAM at C00000, which is slow due to being on the chip bus.
 2048K of expansion RAM, which is fast due to not being accessable by the 
 custom chips.

In a setup like that, the C00000 RAM would be near the head of the list
of available memory because it is detected before the autoconfigure expansion
RAM.  This is not nice, since requests for "fast" RAM would go to the slow
non-chip memory instead of the fast non-chip memory.  FastMemFirst (also
known as SlowMemLast) puts the slow-fast RAM at the end of the list where
it is less likely to get used.

FastMemFirst has no effect if you don't have any expansion memory.
FastMemFirst has no effect if you don't have any memory at C00000 (an A500).

The request for "either type of RAM" tells the system to search the fast-RAM
free list first, then search the chip-RAM free list only if the search of
the fast-RAM list failed.  The searching of the fast-RAM list first is
always done - regardless of whether FastMemFirst has been done or not.

In summary: FastMemFirst is a kludge to make systems with the old Agnus and
real expansion memory run faster.  It is not needed if you have then new
1-meg Agnus.
-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
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