Path: utzoo!attcan!uunet!convex!harper
From: harper@convex.com (David Harper)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 387-20 Async vs. 387-25 Sync performance?
Message-ID: <-1773786503@convex.convex.com>
Date: 13 Feb 90 13:02:01 GMT
References: <2340002@hpldsla.HP.COM> <10643@june.cs.washington.edu> <483@sixhub.UUCP>
Sender: news@convex.com
Organization: Convex Computer Corporation; Richardson, TX
Lines: 27

In article <483@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
>In article <10643@june.cs.washington.edu> luong@grace.cs.washington.edu.cs.washington.edu (Luong La) writes:
>| Yo FLOP's guru,
>| 
>| I owned a 386-25 computer w/ option that I can either install an async 387-20
>| or 387-25 sync. math coprocessor.  My question is :) does the 387-25 sync offers
>| a good bang for my bucks?  I heard that a 387-25 sync can offer about 
>| 0.6 to 1 MFLOPs, how about 387-20 async?  
>
>  I think you mean that you can set the clock for 20 or 25MHz, since I
>never heard of async or sync versions of the 387 

I missed the original posting on this but I would be willing to bet that Luong 
La is refering to a Micronics motherboard.  This is the way that they describe
their 387 setup stuff in the documentation.  Jumpered for 'sync' operation the
387 can be the same speed as the 386 or slightly slower.  I run a 20 MHz 387
in 'sync' mode in the Micronics 25 MHz motherboard and it works fine, although
I have never benchmarked the performance.  Jumpered for 'async' mode you must
supply an external clock oscillator module to run the coprocessor.  This allows
you to put in any speed coprocessor you want.  Thus, 'asynchronous' in this
context means asynchronous to the 386 clock rather than a mode of operation for
the 387.


Dave Harper    -     Convex Computer Corp.            E-mail address:
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