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Path: utzoo!watmath!clyde!cbosgd!ihnp4!qantel!hplabs!hp-pcd!grant
From: grant@hp-pcd.UUCP (grant)
Newsgroups: net.micro
Subject: Re: Amiga
Message-ID: <7100019@hpcvrd.UUCP>
Date: Sat, 14-Sep-85 02:40:00 EDT
Article-I.D.: hpcvrd.7100019
Posted: Sat Sep 14 02:40:00 1985
Date-Received: Thu, 19-Sep-85 07:28:09 EDT
References: <1146@brl-tgr.UUCP>
Organization: Hewlett-Packard - Corvallis, OR
Lines: 17
Nf-ID: #R:brl-tgr:-114600:hpcvrd:7100019:000:819
Nf-From: hpcvrd!grant    Sep 13 22:40:00 1985

{}
>... external memory can run half speed ...

It's easy to assume this if you look at the busing architecture in BYTE.
The custom chips are positioned on a separate 19-bit address bus, which
can only address 512KB.  The external RAM is to be added in a separate 7+
MB chunk according to the memory map.

The conclusion I draw is that the base machine has the 68000 encroach upon
the memory actually allotted to the custom chips.  The custom chips cannot
access more than the 1/2 Meg internal RAM (internally expanded that is).
This means that the external ram completely belongs to the 68000.  Note
that this also means that the internal disk DMA is only good to the
internal RAM; the 68000 has to move it outside.  This last point could be
wrong--I can't find my BYTE right now to check.

Grant Garner  hp-pcd!grant


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