[Linrad] Vista and Windows 7.

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi All,

After having found out that Windows is useless with PCI soundcards
on modern motherboards I made some tests on a not so modern computer. 
A Pentium III at 650 MHz. As it turns out, Windows Vista and Windows 7 
have a very CPU-hungry process, audiodg, that uses up nearly all 
the CPU time on this computer. The tests were without second FFT 
and without any output (no signal clicked.)
http://www.sm5bsz.com/linuxdsp/run/snd-compat/d44-cpuload.htm
(referenced from)
http://www.sm5bsz.com/linuxdsp/run/snd-compat/snd-compat.htm

The conclusion is that Vista and Windows 7 are useless for Linrad on a
Pentium III.

The sad news is that even a Pentium IV is not fast enough for use
of Linrad with the WSE converters under Vista or Windows 7. Occasional
loss of input data causes a time skew between the two RF channels that
would degrade noise blanking and make the polarisation graph non-valid.

I do not think Linrad will work well with MAP65 under Vista/7 on any
computer because occasional loss of data would bring incorrect data 
into the decoder. It seems to me that Vista has bad real-time performance.

I have tested Winrad and it seems the ASIO drivers send data directly
from the hardware to Winrad bypassing the audiodg processes. Finding
out how to incorporate the ASIO API in the mingw package and to use
it properly in Linrad seems to be a too major task. The single channel 
ASIO driver in Winrad does not work properly under Vista while the WMME 
driver works perfectly fine on my Pentium IV (but with a high CPU 
load.) I do not know whether the ASIO problem is Vista itself or something
in the Winrad code that is incorrect for Vista. (I installed Winrad
by running the installer in XP compatible mode.)

Under Windows XP both the WMME and the ASIO input routines of
Winrad run without errors at a low CPU load on the Pentium IV.
It even runs perfectly well on the Pentium III.

My conclusion is the following: Do not use Linrad with soundcards
on computers running Windows Vista or Windows 7. Errors are easily
seen if a single very strong signal is present at the input. 
Errors also manifest themselves as a somewhat too low sampling speed.

The good news is that Perseus, SDR-14 and SDR-IQ do not go through
the Vista sound system so they should work fine. They also do not
use the PCI bus so they run well on modern computers. I do not
yet know Whether Vista creates problems with the digital receivers
on slow computers, but I will have a look at it. I have a feeling
that the Vista latency might be too long to be compatible with the
USB interrupt routines on a 650 MHz processor.

  73

  Leif  /  SM5BSZ



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