Re: ISA Vector card already done...

Al Kossow wrote:
>
> "I certainly look forward to hearing the explanation."
>
> There must have been a low pass filter on the output
> of your DACs..
>
> If you take the output of a voltage output DAC and
> hook it to the input of a scope (which has electrostatic
> deflection and has a very fast beam rate) you should
> see only the initial value and the new value.. two
> dots.
>
> Audio DACs on sound cards always have anti-aliasing
> low pass filters on them, which slowed down the
> slew rate of the DAC output to where you could see
> it on your scope.

Yes, the sound card has the built in filtering. I'm not familiar with
"electrostatic deflection circuitry" but my scope circuitry looks pretty
similar to that of a vector monitor.

Anyway, if that's all it takes, then why not do the exact same to this
project in order to eliminate the high MIPS requirement (add low pass
filtering on the output stage)? Yes, it adds harware, but it seems to
make the whole idea more realistic since the price and availability of
these candidate high power DSP chips was at question earlier.

So, what else am I missing? :-)

Above, you mention that we'd see only the two endpoints on a very fast
display. Isn't this project for a WG or Sega monitor with bandwidths in
the 3-6mhz range? I.e., is it relevant that a very fast display like
that described would be too fast for the project, since the hardware
this is designed for would slew at the right speeds? If we wanted to
make the project work with a faster display, then we would just need to
tweak a parameter that caused it to increase the frame rate
accordingly. (Assuming the DSP can handle the rate ... and we ever
build a faster display. :-) )

Now that you have this vector generator that outputs 1/512 the data as
the original(for a full width line), don't you have all this time to
redraw the line some more in order to make it more visible? That's how
I varied the intensity of my vectors, i.e, how often I redrew them in
relation to how often I drew the others.

So, where to from there? I do appreciate the lesson. Thanks for taking
the time to reply!

Thanks!
Joel-
Received on Wed Mar 25 15:02:38 1998