Text File

Aucbvax.6385 fa.works utcsrgv!utzoo!decvax!ucbvax!works Fri Mar 5 10:31:05 1982 68000 system performance >From NZeck.WBST.PARC-MAXC Thu Mar 4 11:07:10 1982

---------------------------

Mail-from: Arpanet host BRL rcvd at 25-FEB-82 1040-PST Date: 25 Feb 1982 0927-PST From: BISBEY at USC-ISIB Subject: Re: Wicat Graphics To: Works at MIT-AI cc: Bisbey at USC-ISIB Via: Mit-Ai; 25 Feb 82 12:50-EDT Via: Brl-Bmd; 25 Feb 82 13:04-EDT

I too have visited Wicat's Utah offices. The graphics option for the 150-WS is 400x300. Also, the 150-WS is already multibus. We found the unit to be EXTREMELY SLOW. Wicat admitted that there were two wait states per memory access which (they said) slowed the 68000 to 63% of 8 MHZ (that's an effective speed of only 5 MHZ). Rumor has it that someone put a scope on the WICAT and found the 68000 to be running at an effective speed of only 3 MHZ. WICAT was working on a memory board that used 64K chips and a small page table for the first 2 meg. of address space. -------

While I have no bias toward a particular system, I am interested in if anyone has any info on the performance of other 68000 systems (Fortune Systems, Forward Systems etc...)

Is it Wicat's software (I assume it was their opsys that was running not a version of unix) that is slow or is it really the hardware?

It looks like from the 68k specs that for no wait state memory access, the memory access time has to be around one to one an a half clock cycles (125-185 ns) including driving any busses, decoding etc. While this is doable, it puts a on memory. Also if the design includes a memory management unit of some flavor (which would be desirable for os/user protection/dynamic binding), this will add to the required memory performance.

Also note that while the processor is slowed down for a memory access, it still implements the execution phase of the instruction at 8 Mhz.

------------------------------------------------------------

----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen <jgoerzen@complete.org> of http://communication.ucsd.edu/A-News/

This Usenet Oldnews Archive article may be copied and distributed freely, provided:

1. There is no money collected for the text(s) of the articles.

2. The following notice remains appended to each copy:

The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.