Cache controllers, can Xenix use them? -- Xenix yes others no

[John S. Robinson]

In article <195 at icc.UUCP> wdm at icc.UUCP (Bill Mulert) writes:
>There are now a number of high performance 80386 motherboards in
>use in personal computers. Some of these machines have the Intel
>cache controller chip, and 32 to 64k of 30ns ram. Cacheing software
>for MsDos is available for those users. 
>
>My question is, is this cache controller usaeble by any of the
>Unix - Xenix kernels? Does'nt the kernel have to know about it
>in order to use it? Do any of Microport, SCO, Interactive
>support the chip? Would one be wasting ones money to buy a
>machine with a cache controller that would be running Xenix?
>
>-- 
>Bill Mulert                             UUCP:  ukma!spca6 \
>Intercomputer Communications Corp.           decuac!uccba  > !icc!wdm
>Cincinnati, Ohio  45236                   mit-eddie!uccba /
>(513)-745-0500


	I investigated this issue very carefully before purchasing
	a version of Unix for my DELL 310 (a 386 machine with a 82385 cache
	controller) in October of 1988. The products I researched were those 
	of Interactive,	Microport, Bell Technologies, and SCO. The only
	product which had it's processor to memory references mediated by
	the 82385 cache controller when available on a 386 machine was
	SCO(Version 2.3.1).

	Bell Technologies went on to explain that the 'generic' AT&T 386 UNIX,
	which is essentially the same code for Interactive, Microport, and Bell
	Tech., actually 'programs around' the cache controller if a machine 
	had a memory cache controller. The implication of this being that AT&T
	386 UNIX perform better in a machine without a cache controller than 
	on one with a cache controller! This implication was confimed by the
	Bell Tech. tech rep. Before you send flames my way I must reiterate 
	that this was what was told to me by a Bell Technologies tech. rep.
	Repeated calls were made to Interative and the other vendors with 
	essentially the same results. I emphasized to the various tech reps
	that my questions pertained not to the 'caching ability of the unix 
	kernel', but refered to the intel 82385 cache controller.
	In each case it	usually took several days and many call backs, but in
	the end I was able to determine that only SCO would 'claim' that they
	supported the 82385 cache controller. I suspect that this is one of the
	prime reasons that it is taking SCO so dreadfully long to get there
	upgrade to Sys V 3.2 shipped, long after everyone else is shipping 
	product.

	The real issue is though does it make a difference. If only SCO
	supports the 82385, then this would mean that the performance on
	computations that required lots of memory references should 
	be significantly better under SCO than the others. This does seem
	to be the case if one believes the results of the bench marks
	published in the February '89 issue of MIPS magazine where ICS, 
	Microport, SCO 2.3, and ENIX where compared on a DELL 310.
	Unfortunately, the benchmarking method was not done in a way
	that would eliminate other variables such as efficiency of the
	compilers used by the different systems.