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From: BILLW@sri-kl@sri-unix.UUCP
Newsgroups: net.micro
Subject: Re: ecs.366: DEC micro marketing strategy
Message-ID: <3520@sri-arpa.UUCP>
Date: Wed, 27-Jul-83 17:52:00 EDT
Article-I.D.: sri-arpa.3520
Posted: Wed Jul 27 17:52:00 1983
Date-Received: Sun, 31-Jul-83 20:25:30 EDT
Lines: 40

Somebody in a recent message said something like "Id rather have
a DEC 350 than an IBM PC because the 11/23 is nicer/faster than
an 8088".  I don't beleive this to be a true statement.  True
the 11/23 has a much more elegant architechture, BUT:

     a)	I overheard a conversation at the airport in St Louis
	(just before DECUS) to the effect that the 11/23 is
	actually about the same speed as a 4 MHz Z80 processor
	[with the advantages of greater memory addressing capability,
	 of course, plus the availability of a floating point chip]
     b)	I have a detailed spec sheet of the DEC T11 chip (thats
	the 11/23 on a single chip - supposed to be about the same
	speed as a /23) that includes instructin timing information:

	T11 (7.5 Mhz)
		ADD	R0,R1		1.6 uS
		ADD	R0,(R1)		2.8 uS
		ADD	#n,R1		2.4 uS

	8088 (5Mhz)
		ADD	BX,CX		0.6 uS
		ADD	(SI),BX		5.8 uS
		ADD	BX,n		1.6 uS

Notes: the 8088 suffers from its 8 bit bus.  Memory operands that are
	only 8 bits speeds things up, while it doesnt effect the T11
	times.  Also the 8088 being weird, times can depend on exactly
	which registers you use and the like.
	8088 times do not include instruction fetch times. T11 times
	do.  8088 has 4 byte instruction prefetch, 11s dont.
	8088s have no memory protection or mapping.
	11s restrict single process addressing to 64K.

All things considered, I suspect that the 8088 and the 11/23 are
actually about the same speed.  If you could really run all the
existing 11 software on the 350, it would be a clear winner.  You
can't though, and an ugly architecture with available software beats
an elegant architecture with little software.

BillW