System requirements - Was: Out of Space

[Gene Heskett]

On Wednesday 10 August 2016 10:13:19 Ralf Mardorf wrote:

> On Wed, 2016-08-10 at 16:08 +0200, Ralf Mardorf wrote:
> > On Wed, 10 Aug 2016 13:50:07 +0200, Oliver Grawert wrote:
> > > > enough for pro-audio, as 4 GiB of RAM are either, the frequency
> > > > scaling governor just needs to be at a fixed frequency, usually
> > > > "performance".
> > >
> > > why ? do you not trust the kernel devs ? the ondemand governor
> > > will do the right thing if needed and not waste power when not
> > > needed ...
> >
> > That's nonsense, on most machines it does cause xruns. It's a well
> > known issue. JFTR there nearly is no difference in power consumption
> > between ondemand and performance on many machines, I anyway
> > recommend to use it when not doing real-time audio work.
>
> Let alone that an rt patched kernel not necessarily provides the
> frequency scaling governor at all, regarding CPU related issues.

No it doesn't, nor does it supply PAE despite its being in the built 
images name. PAE adds quite some (20+) microseconds to the latency 
response, unsuitable for realtime control. So that is one of the 
casualties of the RTAI patch set.

OffTopic:

I do not run such a kernel on this machine as its setup to simulate only, 
and an amd phenom 9900 quad core running at 2.1GHz on this machine will 
at times have a major fraction of a second response to a scheduled IRQ 
at 1KHz rates. But since theres no machinery out there that would start 
& stop and stutter along, its a visual problem only.

But to give an idea of what CAN be done, the absolute worst case, on a 
dual core atom running at 1.6GHz has a latency of 8,449 nanoseconds, 
with a running average of 3,500 nanoseconds.  Thats 8.5 microseconds 
worst case, average of 3.5 microseconds.

In comparison, this supposed much more powerfull Asus M2N-SLI Deluxe mobo 
with an now old 4 core phenom running at 2.1 GHz, with 8Gb of ram 
machine does 10,092,890 nanoseconds worst case.  Thats 10 milliseconds!

It is not only not in the same ballpark, its not even in the same league.

That Intel D-525-MW board at about a $45 bill when it first came out, was 
the sleeper of the decade for us.  Sadly for us wannabe machinists, its 
been discoed, and the last time I looked for one on fleabay, the price 
had quadrupled. I can buy a mesa pci 5i25 card thats even better for a 
$90 bill and put it in an old used computer for less money.  So thats 
what will be moved to the bigger lathe when I am ready to exercise it 
with a computer. The monitor won't be, its too small and dimming in its 
dotage despite being an LCD.  By now it probably needs new capacitors in 
the CCFL power supply. The first failure mode by far in these modern 
flat screens. I have no clue if the LED backlit versions are any better.

Cheers, Gene Heskett
-- 
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