Doug Webb <
doug....@btinternet.com> wrote:
> In message <snfsk7$bsf$
1...@dont-email.me>
> druck <
ne...@druck.org.uk> wrote:
>
>
> > I think the VIDC might be failing. Does the pointer corruption occur in
> > any particular modes?
>
> The issue occurs in any mode with a StrongARM or Kinetic installed but not
> when a 710 card is installed.
This:
>> I have an issue with a spare RiscPC which exhibits a corrupted Pointer and
>> also a loud buzzing sound from the speaker on initial starting.
points to problems with Cursor and Sound DMA. In other words what's being
fetched from memory for the pointer and the sound is corrupted in some way.
The sound has a separate DMA channel (Sndrq*, Sndak*) from VIDC into IOMD,
but the pointer doesn't. It's separate inside the VIDC but not separate
wiring on the motherboard. So a problem with the Snd wires could cause
glitchy sound, but there aren't any pointer-specific wires that I can see.
If it was all VIDC memory accesses, I would have expected screen corruption
as well (especially when no VRAM).
So either the pointer and cursor DMA parts of the VIDC are failing, or
there's something timing related that affects all memory access and it's
only noticeable during cursor/sound DMA.
The Kinetic doesn't use motherboard DRAM for most things, only for that
needed by DMA (the screen etc). But the SA110 card may exercise the DRAM
more than the 710 does.
A couple of other things to try (separately):
Try switching to a very conservative mode - perhaps mode 27 (16 colour VGA).
That will drop the video bandwidth requirements and make demands on the
memory system 'easier'
Try *Cache Off Things will go slower, but that will push the DRAM harder.
I'm wondering if the behaviour changes.
I'd try these with one SIMM alone, and with one SIMM and one VRAM stick.
If you are able to check them a working RPC that will tell you if they are
known-good.
> Might have to tap out RP16 pack but that is for another day as my old test
> meter has given up the ghost as well.
I wouldn't be tinkering like that without a plausible reason why it might
help. The experiments above might provide information as to what's
happening.
Theo