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Date:      Tue, 26 Mar 1996 08:39:52 +1030 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        rgrimes@GndRsh.aac.dev.com (Rodney W. Grimes)
Cc:        msmith@atrad.adelaide.edu.au, hardware@FreeBSD.ORG
Subject:   Re: Intel P-Overdrive and Opti chipsets?
Message-ID:  <199603252209.IAA01095@genesis.atrad.adelaide.edu.au>
In-Reply-To: <199603251723.JAA04977@GndRsh.aac.dev.com> from "Rodney W. Grimes" at Mar 25, 96 09:23:41 am

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Rodney W. Grimes stands accused of saying:
> 
> > 
> > Just wondering if anyone out there is using an Intel PODP5V
> > (83MHz P Overdrive) in a 486 board based on the Opti 82C895.
> > 
> > I've got one here that won't work unless the internal cache is
> > disabled, however that yields performance around 1/5 that 
> > achieved with a 486DX2/66.
> > 
> > Any ideas?  (Anyone got one of these bastards working at _all_?)
> 
> I have an idea, it is called WB cache coherency, and it probably
> was not implemented correctly on your motherboard.  Does your bios
> only allow yot to disable the internal cache, or can you set it
> to write through mode (like the 486 was).  Several motherboards
> have this as a jumper on the board.

The board supports WB mode, and was previously running with it enabled.
I'm fairly sure that the cache on the board works OK; it's been running
FBSD for over 12mo. with a VLB busmaster SCSI controller.

It wouldn't surprise me if the board is wrong, but I tried all of 
the possible combinations of internal and external cache and WB/WT
modes, and the only significant factor was whether the PODP internal
cache was on.

> This is a common problem with the PODP processors :-(

Think I'm resigned to hunting a new MB for this box.  *sigh*
Thanks for the suggestions.

> Rod Grimes                                      rgrimes@gndrsh.aac.dev.com

-- 
]] Mike Smith, Software Engineer        msmith@atrad.adelaide.edu.au    [[
]] Genesis Software                     genesis@atrad.adelaide.edu.au   [[
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