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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.arch
Subject: Re: The 360 was a design landmark  (360 vs vax)
Message-ID: <26610@sun.uucp>
Date: Wed, 26-Aug-87 15:56:41 EDT
Article-I.D.: sun.26610
Posted: Wed Aug 26 15:56:41 1987
Date-Received: Sat, 29-Aug-87 03:56:52 EDT
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> OK, so if you implement a VAX using the same technology as a top-of-the line
> IBM mainframe, how fast would it be?

For some further amplification: from the February 1987 issue of the Digital
Technical Journal, on the VAX 8800 family, the cycle time of that family is
45ns.  A single-processor 8550 or 8700 is claimed to have a "sustained
applications throughput" of 6.0 times an 11/780.

From Mike Taylor's article on the Amdahl 5890s, the cycle time of that family
is 15ns.  A single-processor 5890-190E is claimed to have a MIPS rate 33 times
that of an 11/780 for a typical UTS workload.

I have no idea how the workloads DEC and Amdahl used compare.  Assuming they
are comparable, and assuming that the performance difference between the two is
solely due to 1) the Amdahl having a cycle time of 3x that of the VAX and 2)
the 370 architecture permitting you to build a faster box, the performance
increase due to the 370 architecture is about 1.8x.  Not shabby, but not 20/8 =
2.5x either.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com