Article View: comp.sys.transputer
Article #2234Re: T800 Memory Design
From: Moshe Braner
Date: Sat, 08 Oct 1988 20:37
Date: Sat, 08 Oct 1988 20:37
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1521 bytes
[] The Inmos documentation (I forget which book, I think it's one of the little red ones) says that the number of extra machine cycles needed to access external RAM is at least 3 and more typically 5, depending on your hardware setup. They have a table of the effect of putting code, data, or both in external RAM on the execution speed of a couple of benchmark programs. The upshot is that relative to running everything inside the transputer's on-chip RAM, putting code outside slows things down by a factor of about 1.3, putting data outside slows by 1.7, and putting both outside means about a 2-fold slow-down. Note that data has a larger effect than code, perhaps because the transputer reads code 4 bytes at a time and each instruction is usually only 1 byte. So put the workspace of your most time-critical function on-chip, and use local variables in preference to globals, and you're going to get almost full speed. - Moshe Braner
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!purdue!mailrus!cornell!batcomputer!braner From: braner@batcomputer.tn.cornell.edu (Moshe Braner) Newsgroups: comp.sys.transputer Subject: Re: T800 Memory Design Summary: External RAM slows it down by a factor of 2 or so Keywords: Transputer, Memory Message-ID: <6497@batcomputer.tn.cornell.edu> Date: 8 Oct 88 20:37:49 GMT References: <502@koel.rmit.oz> Reply-To: braner@tcgould.tn.cornell.edu (Moshe Braner) Organization: Cornell Theory Center, Cornell University, Ithaca NY Lines: 18