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Date:      Fri, 11 Oct 1996 12:04:07 -0500 (CDT)
From:      Robert J Fowler <rjf@cs.rice.edu>
To:        hardware@freebsd.org
Subject:   AMD 586 runs FreeBSD just FINE (fwd)
Message-ID:  <199610111704.MAA20346@una.cs.rice.edu>

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Matthew Gessner announced --
> 
> Hello, all,
> 
>   A little status report for y'all.
> 
>   I just bought one of those them there fancy shmancy CPU upgrades.  I
> had an Intel 486/DX266 and upgraded to a AMD 586/133 from Ganberry via
> Micro Warehouse.  For $140 I have a machine that runs about 2.5 x
> faster!
> 
>   And no problems with BSD!  Yeah!
> 
>   I was a little worried having read reports of problems with Cyrix
> chips, but so far, so good!  If I notice anything, I'll report it.
> 
>   Matt
> --

Just to add another data point...

I've got a 486 box at home that I also upgraded to an AMD 586/133 from
an AMD DX/2 at 80 MHz.  Since my motherboard could provide 3.3V and it
has a not too ancient BIOS, the packaged upgrades from Gainberry and
Evergreen really don't offer any added value over just getting just
the 586/133 chip. I paid $60+tax from Electrotex here in Houston. 

The 586/133 is essentially just a 486 with clock tripling/quadrupling
and a bigger writeback cache.  My no-name VESA motherboard/BIOS
doesn't have documented support for writeback nor clock quadrupling.
Despite suggestions from helpful hardware hackers that I dike off the
appropriate pin on the CPU package (See the datasheet.) to get it to
quadruple, I decided to take a more conservative approach.  Therefore
I'm running the system in writethrough mode and clock tripled mode
over a 40 MHz local bus, i.e.  the CPU core is running at 120.  I am
paying a penalty for using writethrough vs. writeback, but I've been
insufficiently motivated to try to uncover an undocumented writeback
mode.  As expected, performance on CPU intensive stuff is therefore a
bit over 50% better (Remember the bigger cache than it was before.
See the AMD web page for documentation, including the datasheet. 

The system has been rock solid for about 3 months running FreeBSD or
Windows. 

-- Rob



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