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Re: Damon, Why CF ?


PERILLE (05:27 AM 08.06.2000) wrote:

 >Example : 8 playback + 1 recording stereo channels @ 48khz/16bit
 >
 >SmartMedia :
 >- 32 READ bytes*70nsec + 4 RECORD bytes*660nsec = 4.9µsec*48khz = 24% =>
 >PASS
 >
 >CompactFlash :
 >- 36 bytes*660nsec = 23.8µsec*48khz = 114% => CRASH !

Am I correct in seeing you outline a total of 9 stereo tracks here?

Repeater is obviously laid out as a 4 track machine which we're _assuming_ 
to be 4 stereo tracks. I don't think that Damon has said anything about 
sample rate, but I would be more likely to assume 44.1khz over 48khz.


I personally have an easier time looking at the situation by defining the 
data quantity first and then looking at the bandwidth required. In doing 
so, I come up with:

   1 sample * 16bits/sample    = 2 bytes/sample
   2 channels/track            = 4 bytes/sample/track
   4 stereo tracks             = 16 bytes/sample total

     16 bytes/sample *
       44100 samples per second  = 705600 bytes/second
   - or -
     16 bytes/sample *
       48000 samples per second  = 768000 bytes/second

Then, working from your numbers of:

   - typ. rate : 250nsec/word + PCMCIA/ATA bottle necks = 1.5MB/sec
     (660nsec/byte)

It seems that at "full load" Repeater would be running the media at less 
than 1/2 of it's potential throughput. I fully admit that I may be missing 
something... Please correct me if I'm wrong.


Do you happen to have a URL for a CF or SM manufacturer with these 
throughput numbers published?

Mark