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Re: [Discuss-gnuradio] interfacing a DSP array card to USRP2

From: Jeff Brower
Subject: Re: [Discuss-gnuradio] interfacing a DSP array card to USRP2
Date: Wed, 31 Mar 2010 15:32:44 -0600 (CST)
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>> From: Jeff Brower <address@hidden>
>> Firas-
>> A couple of brief comments:
>> 1) Sounds like this was a
>> high-speed data acq card, optimized for streaming, not an accelerator
>> card.  How big was the
>> FIFO?
> The FIFO was 64MByte.

That's huge... and you mentioned a 64k block transfer, much smaller, but still 
more than 40 times a large Ethernet
packet.  It sounds to me like this particular card mfg was focused on very high 
rate streaming (without gaps or drops)
and not on low-latency, small transfers.  I would guess they didn't set up 
their driver to optimize small transfer
sizes.  Maybe even the board didn't support a small size, for example if the 
FIFO had to contain a minimum number of
channels and/or data length before it could assert "not empty".


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