Path: chuka.playstation.co.uk!news
From: Andrew Partington <andrew.partington@harbinger.com>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: negative scrolling on homebrew map routine - need help!!
Date: Wed, 21 Mar 2001 13:06:25 +0000
Organization: PlayStation Net Yaroze (SCEE)
Lines: 67
Message-ID: <3AB8A751.A5D36CCF@harbinger.com>
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Thanks Peter, that worked 100%!  But now I can't see how many HSyncs/frame I am
getting - is there any way I can get my VSync(0) value back using callbacks
without causing another wait for vertical retrace?  (calling VSync with values
greater than 0 doesn't seem to return anything useful)

I also tried setting the stack to point at the DCache, as in the the NY FAQ.
The given asm wouldn't work for CW though, so I tried to come up with something
I thought was equivalent...

volatile asm void SetStackToDCache()
{
    sw $29,0(sp)                        // Put R3000 register 29 (stack pointer)
onto stack
    lw $29,0x1f8003f0               // Point at the upper bound of DCache (since
the stack grows downwards)
}

volatile asm void SetStackToR29()
{
    lw $29,0(sp)                        // Restore stack pointer
}

Trying this out, (not surprisingly perhaps, since the first item of the stack
might have had some useful value in it) I got the black screen of death!  I know
the DCache is only 1K but I don't think I was putting enough params on the stack
to overflow it (unless setting the project to build with maximum optimisation
has reorganised the code somewhat, or I may need a delay slot to be filled with
nop after the load).

Can anyone see what I am doing wrong?  Also, do I set the stack to point at the
DCache as the very first thing in the initialiation code, or only before a
time-critical procedure call (resetting it afterwards)?  Or would a better
approach be to just dump structures into the DCache as needed without touching
the stack pointer?

Cheers everyone! [crikey, this thread's getting hefty innit!  Not that i'm
complaining :)]

Andy

Peter Armstrong wrote:

> "Andrew Partington" <andrew.partington@harbinger.com> wrote
> >
> > Last night I attempted using VSyncCallback() for the first time to attempt
> to
> > get more raster time (as explained in the Net Yaroze FAQ), but I couldn't
> get it
> > working [so I went away and had a look at some other optimisation measures
> > instead, none of which seemed to have much effect :( ]
> >
> > I had something like:
> >
> > (in my globals section of my code)
> > volatile int waitVSync = 0;
>
> There are problems accessing global variables from within the callback
> function. Try declaring your variable as
>
> __declspec(bss) volatile int waitVSync = 0;
>
> This should work.  There's also another method, which involves restoring the
> gp register value, check out the CW doc Targeting Net Yaroze, page 66/67 for
> more info.
>
> Peter