Re: A couple of questions...

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Angus Dorbie (dorbie++at++sgi.com)
Fri, 17 Jul 1998 10:48:16 -0700


Angus Dorbie wrote:
>
> markc++at++io.com wrote:
> >
> > Hello,
> >
> > First off -- my configuration.
> > --
> > Onyx2, 6 195mhz r10's, 2 pipes, 6 rms.
> > IRIX 6.4
> > Performer 2.2.
> > --
> >
> > My first question regards PFCHAN_SWAPBUFFERS_HW, is there any performance
> > gain to be realized by genlocking two pipes ? I've gotten some
> > conflicting info on this, and expect that my friend was really talking
> > about PFPHASE_LOCK.
>
> The real gain is for genlocking. You must genlock for good performance,
> especially at high frame rates, and it looks better.
>

The stuff above here is OK.

> When on a single host there's a marginal benefit for genlocking the
> pipes. The real win for genlock is when you have two separate machines,
> and so the additional communications latency for the swap sync
> eliminated

Oops, the above paragraph should read as follows:

"When on a single host there's a marginal benefit for swapreadying the
pipes. The real win for swapready is when you have two separate
machines,
and so the additional communications latency for the swap sync
eliminated."

i.e. substitute genlock for swapready. Sorry for the confusion.

The stuff below this is OK.

Cheers,Angus.

>
> >
> > Also, exactly how does one cable up a two (or n) pipe machine
> > to SWBUFFERS_HW ? I've gone through the archives, Onyx hw docs,
> > etc. And despite finding some info, even a recent thread on
> > info-performer. I'm still uncertain...
>
> Once you have daisychained the genlock you can wire all pipe swapreadys
> on a single wire. Here,s a 3 pipe example:
>
> PIPE 0 PIPE 1 PIPE 2
> [ ] []GEN IN []GEN OUT []GEN IN []GEN OUT
> \ / Video / \ / \/
> \ / out / \_________/ 75 Ohm
> ||\ / terminator
> ||\\___________/
> || \ H/C wire with
> || \ Composite Sync
>
> Swapready Swapready Swapready
> [] [] []
> \ \ /
> \______________________\_____________________/
> T Junction
>
> Cheers,Angus.
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