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From: mconway@hpcuhc.cup.hp.com (Michael Conway)
Newsgroups: comp.sys.hp
Subject: Re: Software TLB : a PA performance enhancement ?
Message-ID: <530038@hpcuhc.cup.hp.com>
Date: 21 Jun 91 17:44:48 GMT
References: <1991Jun20.151803.170@and.cs.liv.ac.uk>
Organization: Hewlett Packard, Cupertino
Lines: 22

>From djn@cs.liv.ac.uk 

>According to the manual Software Lookaside Buffers may help the
>performance of Precision Architecture Machines with small 
>Hardware TLBs. Perhaps someone from HP would give an assessment
>of the adequacy of the TLB on the HP-635. Suggested values for 
>the 'nstlbe' kernel config parameter would also be welcolmed.

The software TLB is intended for use on systems with very small hardware
TLBs such as the 808 and 815 which only have 64 entries.  It is not supported
on any other processors.

I assume you are referring to an HP 9000 Model 635; if so the TLB has 4096
entries.  This should be sufficient and the software TLB (even if it could 
be used) would not add any value since it uses (expensive) memory 
references to maintain the table.


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