[hpsdr] VMs and USB2

[Bill Tracey]

Hi Bob -- disappointed to hear of your VMWare issue -- I was hoping 
to bring up a big quad core box with VMWare running different OS's to 
play HPSDR on.

As to what may be the cause of the problem -- latency and  perhaps 
turnaround time.  For 192khz our inbound data rate is about 12.4 
Mbits/sec (192ksamp/sec * 64 bits/sample) + 1.6% overheard for sync 
and command and control (8/512).  Outbound the data rate is about 3.1 
Mbits/sec, so it would appear we should have plenty of bandwidth.

There is another possibility -- if you're using the 4 Feb PowerSDR 
code I've got a thread reading the spectrum data from EP4.  At the 
moment that thread is reading data from EP4 as fast as it can be 
delivered.  I don't think there's all that much data coming up the 
EP4 pipe, but I've not measured it yet.  If you did have the 4 Feb 
drop I can build one with the EP4 stuff turned off and see if that 
makes any difference.

Regards,

Bill (kd5tfd)


At 04:23 PM 2/5/2009, Bob Cowdery wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>I should have done these very simple tests before I started but
>hindsight is a wonderful thing.
>
>I copied a 288MB file from a USB stick to my hard drive. All systems are
>reporting a USB device at 480Mbps (although it's hard to get info out of
>XP).
>
>On my host Ubuntu system this takes 12 seconds.
>On the VM's both Ubuntu and XP it took 45 seconds.
>
>This is 4 x slower so it should equate to about 120Mbps. In practise we
>seem to be going about 1/2 speed anyway accounting for protocol, the
>stick itself and disc write times I suppose that's reasonable.
>
>Why would this not be way more than is needed to transfer 48k at 24 bits
>and 48k back at 16 bits. What am I missing here?
>
>73
>Bob
>G3UKB



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