Re: [Xpert] Re: [rtl] Re: Virge DX and accel. introduced latency? (was Re: [Xpert]XFree86in realtime applications)

[Mark Vojkovich]

On Sat, 25 Nov 2000 [EMAIL PROTECTED] wrote:

> 
> Andrew Morton reports that the S3 and Matrox cards are known to 
> have problems giving up the PCI bus.

   On many cards, Matrox for sure, it's virtually impossible
to prevent PCI disconnects from happening.  Matrox discusses
this in their documentation, for instance, the G400 docs,
section 4.1.2

 "PCI Retry Handling

   In certian situations the chip may not be able to repond
to a PCI access immediately, therefore, a number of retry 
cycles will be generated.  A retry will be asserted when:" ... 

  [ a whole mess of cases including direct framebuffer accesses ]

  For real-time platforms you folks probably need to be using
old ISA cards or something.  Some PCI chipsets make the retry
problem worse.  LX chipset is infamous.


                        Mark.

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