Article View: net.micro.atari16
Article #1468Re: 68000 Memory Managment
From: Jeff Lee
Date: Sun, 31 Aug 1986 03:48
Date: Sun, 31 Aug 1986 03:48
23 lines
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1989 bytes
In article <937@cit-vax.Caltech.Edu> wen-king@cit-vlsi.UUCP (Wen-King Su) writes:
> The high speed CAS only block transfer
>operation available in many DRAMs is rendered useless since contiguous
>column addresses in a DRAM chip are no longer contiguous in 68K's
>address space.
If you are talking about nibble-accessible rams, the ones that I saw
operate only on mod-4 boundaries and each time you strobe the CAS they
return the next bit circularly (mod-4). Since the memory management
schemes that I am familiar with use 2^N boundaries (N > 2), this should
be no problem. But then, you might be talking about another (even newer)
type of ram that I'm not familiar with.
Speaking of which, does anyone know of a REAL (ie - available off the
shelf, now) system that actually uses the nibble mode of some of the
newer rams. It looks like a great way to load your cache quickly with
some of the bus-hog multiprocessors that are becoming available now
(Encore, Sequent, etc...). They already load 64 bits of memory at a time
onto the separate processor cards when they need to hit main memory.
--
Jeff Lee
CSNet: Jeff @ GATech ARPA: Jeff%GATech.CSNet @ CSNet-Relay.ARPA
uucp: ...!{akgua,allegra,hplabs,ihnp4,linus,seismo,ulysses}!gatech!jeff
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!seismo!gatech!jeff From: jeff@gatech.CSNET (Jeff Lee) Newsgroups: net.micro.atari16,net.micro.amiga,net.micro.68k Subject: Re: 68000 Memory Managment Message-ID: <4422@gatech.CSNET> Date: Sat, 30-Aug-86 23:48:29 EDT Article-I.D.: gatech.4422 Posted: Sat Aug 30 23:48:29 1986 Date-Received: Sun, 31-Aug-86 05:07:51 EDT References: <508@elmgate.UUCP> <64@mit-prep.ARPA> <510@elmgate.UUCP> <417@atari.UUcp> <271@dmsd.UUCP> <937@cit-vax.Caltech.Edu> Reply-To: jeff@gatech.UUCP (Jeff Lee) Organization: School of Information and Computer Science, Georgia Tech, Atlanta Lines: 23 Keywords: 68000 atari amiga 68k mmu