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Date:      Fri, 11 Aug 1995 10:20:36 -0700 (PDT)
From:      "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com>
To:        mrcpu@cdsnet.net (Jaye Mathisen)
Cc:        bugs@freebsd.org
Subject:   Re: Performance problem resolved.
Message-ID:  <199508111720.KAA04273@gndrsh.aac.dev.com>
In-Reply-To: <Pine.BSD/.3.91.950811082346.8849h-100000@schizo.cdsnet.net> from "Jaye Mathisen" at Aug 11, 95 08:25:48 am

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> 
> 
> 
> Hmmm, well, I'm not sure why the VGA card on a PCI slot even gets an 
> interrupt, but moving everything to IRQ 15 seemed to solve the problem.

Some VGA PCI bioses call the PCI bios and request an interrupt along with
there block of I/O ports at PCI P-n-P configure time.  This is for
video cards that support vertical retrace interrupts (usefull for doing
3D split image display with shutter glasses).

IMHO, it is a mis feature that should be disableable, but unfortenatly
there is no way to turn it off (other than blowing a new PROM for the
video card, removing the request for the interrupt, and disabling the
logic that allows it to be created).

Almost all ISA cards that could generate an IRQ2 had a way to turn it
off so you could free that interrupt up for other use.  Well, the PCI
P-n-P folks forgot all about that nice little feature of jumpers and
have taken all control of such things away from us users.

P-n-P is creating headaches for fully loaded machines running out of
interrupts due to this bit of braindamage :-(.

Design computers that even an idiot can use, and only an idiot will use
them :-(.

> Transfers are now humming along at a nice 900+Kbps, which is more what I 
> expected.

:-)

> Assuming INN compiles fine, I'll be jammin'.

You should be jamming buy now :-)

> Thanks for the help everybody.
> 


-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD



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