Re: DAC rates

>I'm having a little trouble parsing this..
>
>Guess I should have asked for more detail on WHAT was being
>designed :-)
>
>>From the message exchange, I'm assuming 12 bits of resolution in
>X and Y. At what rate can these X and Y values change? I was
>assuming the rate of change was fairly slow, but thinking about
>it, it is going to be the rate at which the beam will move to
>the next x,y position on the screen, which can be quite fast..
>
>I'm guessing this is the "6Mhz" in Zonn's message.

The maximum "update speed" of a DAC in something like Asteroids is 3MHz.
(the speed of the vector clock) Actually, because of the binary rate
multiplier it's:

(63 * 3MHz)/64 = 2.953MHz...

That just gives you "Asteroids" level vector performance. I was hoping for
2-4 times that for whatever design I try.

So for dual, 12-bit, serial DACs to meet Asteroids level performance...

3MHz DAC rate
minimum of twelve clocks per update
two DACs for X/Y

3MHz * 12 * 2= ~72MHz

Ugh. And like Zonn said, that's without any register-type steering
overhead for the serial link. "Hello, parallel DACs." :-)

-Clay

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
\/ Communications Division http://www.supra.com/
Received on Thu Dec 18 10:43:54 1997