Path: utzoo!utgpu!cunews!bnrgate!bigsur!bnr-rsc!mascot@bnr.ca
From: mascot@bnr.ca (Scott Mason)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: A500 HD and memory expansion questions
Summary: A501 trapdoor memory expanders only provide Slow-Fast Memory
Keywords: memory, fast, expansion
Message-ID: <4314@bnr-rsc.UUCP>
Date: 10 Apr 91 19:41:18 GMT
References: <9104082116.AA23378@lilac.berkeley.edu>
Sender: news@bnr-rsc.UUCP
Organization: Bell-Northern Research, Ottawa, Ontario, Canada
Lines: 27

In article <9104082116.AA23378@lilac.berkeley.edu> ECZ5ACK@MVS.OAC.UCLA.EDU (Andy Kohler) writes:
>
>   I'm just about to add a hard drive and 4 megs of memory to
>my A500, and I have a couple questions.  I've decided to get the
>GVP Series II controller and Quantum 80 or 105 meg drive, but
>I also want to increase memory.  Should I get 4 megs of RAM in
>the controller (rather expensive) or buy a Baseboard w/4 megs
>($299)?  What are the advantages/disadvantages of each way?
>

The Baseboard, which plugs into the trapdoor expansion, is interfaced
via the Chip Bus. In the future, it would be theoretically possible
to use memory installed on the Baseboard to expand Chip Memory. This
would likely require support on the Baseboard, and may involve an
upgrade of your Angus custom chip. A501 expanders are sometimes used
in this fashion (see other postings in this group).

Memory on the Baseboard which is not accessible to the custom chips
is allocated as Fast Memory. However, because it is interfaced with
the Chip Bus, it cannot be used by the processor whenever the custom
chips are accessing chip memory. This memory is often called Slow-
Fast memory, because it is allocated as Fast memory but cannot usually
be accessed as quickly as true Fast memory. True fast memory, such as
that installed in accessories interfaced to the expansion port, are
interfaced to the processor via the Zorro bus.

Scott.