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Re: [Discuss-gnuradio] Good laptop for GR/USRP

From: Martin Dvh
Subject: Re: [Discuss-gnuradio] Good laptop for GR/USRP
Date: Tue, 20 Mar 2007 22:59:48 +0100
User-agent: Debian Thunderbird 1.0.2 (X11/20070113)

Bahn William L Civ USAFA/DFCS wrote:
> We will (hopefully) be purchasing some new laptops specifically for use
> with the USRP and wanted to get any recommendations on particularly good
> machines to purchase or, failing that, what specs to focus on.
> This is my present thinking - please correct any misconceptions I have:
> 1) Dual core is probably a very good way to go, especially since our
> applications are going to involve a signal processing thread and a
> control thread.
> 2) We want to get as much processor speed as we can get.
> 3) Memory probably isn't a huge concern. We will probably be getting 1GB
> of ram.
It is, if you want to use a ramdisk. See note below.
Also memory speed and cache size is important to gnuradio. Between each 
gnuradio block, data is put in small memory buffers.
A too slow memory or too small cache will probably have a big impact on 
processing speed. I haven' t benchmarked this though.
> 4) In order to capture long data sequences, it would be nice to have a
> speedy throughput to the hard drive. What is a good solution here - as
> in what is a reasonable set up that is considerably faster than the
> run-of-the-mill hard drive and controller? (When all is said and done,
> we'll live with what we get, this isn't super important to us).
If you can, get something with a real-world sequential read and write speed of 
over 32 MB/sec.
32 MB/sec is the maximum datarate to and from the USRP.

If you can't find a disk with this throughput, put in a whole lot of ram. I 
regurlarly use big ramdisks when working with gnuradio.
They are allways fast enough and have allmost no processor load. After use, you 
can then store the files permanently to disk.

Another option is using a notebook which supports an extra disk in a bay. This 
way you can make a raid stripe-array.

Any way, get a big disk. You will get a lot of data.

> 5) What processors should I consider and/or avoid? My understanding is
> that GR leverages the advanced floating point capabilities of modern
> processors, but I have no idea which ones are particularly good or
> particularly bad.
I have good experience with athlon64. But I don't know about core-duo. It is 
probably faster.
> 6) How much does the video card affect things? Does it affect non-GUI
> applications very much (as in, does GR use the processing capabilities
> of today's video cards in any significant way for non-video
> processing?).
At the moment, the videocard does not play a big role. It is only used for 
displaying the GUI, which does not need any special videocard.

I have been working on a gpgpu version of gnuradio which WILL use the 
processing power of the videocard.
For some gnuradio blocks, the performance is very promising (FIR filters) but 
for a lot of others the implementation is very difficult or
impossible or just doesn't perform well (PLL, IIR, blocks with integer and 
boolean code).
The problem is that combining gpgpu and non-gpgpu blocks gives a performance 
penalty due to the copying of data back and fourth between the
host-memory and the videocard memory through the PCIe or AGP bus.
As videocards get more and more capabilities, and the API to the videocard is 
expanded (nvidia CUDA and ATI CTM) I suspect that at some point it
will be possible to develop a gnuradio version whcih would run for the most 
part in the videocard.
But this will not be in the near future, so I wouldn't spend a lot of money on 
a videocard in a notebook for gnuradio now.

7) Test the usb throughput of the notebook. Not all chipsets, even from modern 
computers, will sustain 32 MB/sec in real-world applications.
Benchmarks are hard to find about this on the internet. The best way to know is 
to test it yourself or ask people here on the list on their

I hope this helps.

Martin Dudok van Heel
> Thanks a lot!
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