Re: ISA Vector card already done...

On Wed, 25 Mar 1998 18:02:42 -0500, Joel Rosenzweig <joel-r@an.hp.com> wrote:

>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.

Scopes use charged plates to move the beam around, monitors use a yoke.

Charged plates are much nicer, yokes are much cheaper.

>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?

Don't confuse bandwidth with slew rate, the slew rate is much slower and not
rate as a frequency. Usually as inches per microsecond.

Bandwidth is high fast it can turn off and on a beam (or change from one color
to another.)

-Zonn

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Received on Wed Mar 25 15:41:04 1998