Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site chronon.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!gamma!epsilon!zeta!sabre!petrus!bellcore!decvax!decwrl!pyramid!chronon!eric
From: eric@chronon.UUCP (Eric Black)
Newsgroups: net.micro.amiga
Subject: Re: Loading external RAM from disk
Message-ID: <168@chronon.UUCP>
Date: Thu, 6-Mar-86 14:58:09 EST
Article-I.D.: chronon.168
Posted: Thu Mar  6 14:58:09 1986
Date-Received: Sat, 8-Mar-86 21:47:38 EST
References: <282@cernvax.UUCP>
Organization: Chronon Computer Corp., Mtn. View, CA
Lines: 29


> Thorsten von Eicken         tve@cernvax.UUCP writes in <282@cernvax.UUCP>:
>   The other day I wondered how a program could be efficiently loaded into
>expansion RAM. Remember the custom chips can only access the internal 512K
>and disk DMA is handled by one of these chips.
>
>   If I interpret this correctly, to load a program or data into  external
>memory  requires  it  to be first put into internal RAM and then copied by
>the 68000 (!) into external RAM.
>
>   Should this be correct, a 68010 would really be worth  it  as  soon  as
>external RAM is added.
>
>   Did I overlook anything ?

What you overlooked is that the expansion bus is a full 68K bus, and that
any expansion device plugged onto it can become the bus master (assuming
that it asks nicely).  An external disk controller hopefully will include
a DMA controller of its own.  Using the DMA provided by the internal custom
chips is probably not possible, and is not desirable.  Note that DMA from
the external disk to "fast RAM", e.g. for program loading, can go on
completely in parallel to internal access to "chip mem", e.g. video.
-- 
Eric Black   "Garbage In, Gospel Out"
UUCP:        {sun,pyramid,hplabs,amdcad}!chronon!eric
VOICE:       (415) 941-0403
US SNAIL:    Chronon Computer Corp.
	     2570 El Camino Real W.   Suite 206
	     Mountain View, CA   94040