[hpsdr] computer performance

[mikea]

On Mon, Jun 25, 2007 at 12:36:09PM -0700, FRANCIS CARCIA wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> 

> Hi All,
>   I wonder if I was fooling myself thinking I could make a USB2 PCI
>board function as a good interface for HPSDR. I wonder what kind of
>machine will be required when the next cards come on line. I'm told
>500 meg of ram isn't enough to run the XP pig with big applications.

>   Any suggestions so I only have to upgrade once? frank 

As to the USB2 interface: what leads you to believe that the PCI board
or, for that matter, a USB2 PCMCIA (or "PC") interface won't be good 
enough for HPSDR?  USB2 is _fast_; full-tilt-boogie USB2 runs 480 Mbit
per second. FireWire appears to run up to 800 Mbit/sec, which is close 
to double. Either one is going to make your CPU work hard to keep up
with the input. 

My little Windows 2000 1GHz lapdog with 1 GByte RAM has trouble
keeping up with my SDR-IQ, and it's very obviously the CPU that's the
bottleneck: I can run fine with 100 KHz bandwidth, but 150 KHz or 192
KHz bandwidths cause SpectraVue to miss updates, to produce clicks and
dropouts in the audio, and sometimes to stall or hang. Trying to run
any other application with SpectraVue also generates problems -- not
swapping, AFAICS, but just CPU shortage.

I anticipate at least the same order of problems from the HPSDR suite,
as it will need to do much the same thing. This will, I think, turn 
out to be something for which the answer really is throwing CPU -- a 
_lot_ of CPU -- at the problem. RAM will be necessary in proportion, 
and more won't hurt. 

For a good first approximation to what you'll need, max your computer
out on RAM. Keep as much data as possible in RAM; disk is terribly 
slow by comparison. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin 

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