Thread View: comp.sys.transputer
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Started by David Abramson
Wed, 05 Oct 1988 01:12
T800 Memory Design
Author: David Abramson
Date: Wed, 05 Oct 1988 01:12
Date: Wed, 05 Oct 1988 01:12
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I have been searching the T800 documentations for information on the effect of external memory speed on processor speed. Does anyone have this information? The only reference I can find is that an internal memory operation takes 1 cycle. Is it possible to have the T800 runnning at full speed with external memory? What is the effect of slower memories. Dr David Abramson ACSnet: rcoda@koel.co UUCP: ...!uunet!munnari!koel.co.rmit.oz!rcoda CSNET: rcoda@koel.co.rmit.oz ARPA: rcoda%koel.co.rmit.oz@uunet.uu.net BITNET: rcoda%koel.co.rmit.oz@CSNET-RELAY PHONE: + 61 3 660 2095 Commonwealth Scientific and Research Organisation, Division of Information Technology, c/o Department of Communication & Electronic Engineering, Royal Melbourne Institute of Technology, P.O. Box 2476V, Latrobe St, Melbourne, 3000, Australia
Re: T800 Memory Design
Author: Moshe Braner
Date: Sat, 08 Oct 1988 20:37
Date: Sat, 08 Oct 1988 20:37
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[] 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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