Re: Problem w/ Matrox Millenium

[Terry Matula <tmatula@felix.TECLink.Net>]

Hello John,
I am a developer that may be experiencing this problem.  Would this
unnamed
vendor happen to be Cirrus Logic with their GD5436?

John R Pierce wrote:
> 
> While I haven't worked with the Matrox, I know that a certain other popular
> graphics chip family will generate hellaciously long retry cycles if improperly
> programmed.  The chip vendor was telling everyone that they could throw data at
> the FIFO just as fast as they wanted without worrying about fifo overruns as
> the chip could consume data faster than the CPU could generate it.  Well, thats
> just not true.  At 24 or 32bit/pixel, writing 32bit words of monochrome data
> generates 32x4bytes of internal RMW memory cycles PER dword written... If you
> did what the vendor suggested and REP MOVSD a large font glyph to the chip, you
> would generate very long abort/retry cycles which would interfere with the
> hosts interrupt latency, and even ISA dma cycles (like sound blaster audio).
> It took a fair amount of tricky tuning with a PCI bus analyzer to prevent this
> from happening without impacting performance (in graphics, speed is everything,
> products are made or broken by a few lousy winmarks...)  Earlier versions of
> this unnamed vendors chips did not implement retry correctly, so were simply
> generating WAIT states that could stretch for 100's of cycles, seriously
> violating PCI timing specifications.  This, needless to say, was even worse.
>ŒÜÌ