Path: utzoo!mnetor!uunet!steinmetz!sungoddess!oconnor
From: oconnor@sungoddess.steinmetz (Dennis M. O'Connor)
Newsgroups: comp.arch
Subject: Re: What's Significant about Harvard Architecture?
Message-ID: <9741@steinmetz.steinmetz.UUCP>
Date: 1 Mar 88 19:17:57 GMT
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Reply-To: sungoddess!oconnor@steinmetz.UUCP
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Organization: GE Corporate R&D Center
Lines: 31
Keywords: Hahvahd

An article by uuuj@vax1.UUCP (Rodney Recker) says:
] I've now seen several references to Harvard Architecture and am
] wondering what it really is that qualifies an architecture as
] "Harvard". Any explainations or references would be appreciated.
] 
] Thanks in advance!
] 
] Rod Recker

"HARVARD" architectures have seperate memory systems for instructions
and operands. Separate busses connect each memory system to the CPU.
The name is historical, I believe : one of the very early machines
that had this architecture was built at Harvard.

The idea is old, but has aquired popularity recently as
a method to method the CPU/Memory bandwidth bottleneck
in microcomputers.

A varient of it is to hae separate instruction and data
busses to seperate instruction and data memories, but 
with a shared address bus.

Most Harvard architectures need to "dual-port" the
instruction memory onto the operand memory. Often
Time-Division Multiplexing is used, at a rather course scale,
essentially by placing a DMA channel between the I and D memories,
rather than true dual-port memory or fine-grain TDM.
--
    Dennis O'Connor			      UUNET!steinmetz!sunset!oconnor
		   ARPA: OCONNORDM@ge-crd.arpa
   (-: The Few, The Proud, The Architects of the RPM40 40MIPS CMOS Micro :-)