[linux-audio-user] Newbie Questions

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Sat Mar 19 21:14:28 EST 2005


On Sat, 2005-03-19 at 03:45, bjay at SAFe-mail.net wrote:
> Hi, just spent a month getting a linux audio workstation going and I've got a load
> newbie questions I have'nt been able to solve, or find answers to; some technical, some bigger picture :
> 
> Machine Specs
> -------------
> Uniwill 340s2 (Advent 5480DVD) laptop
> 384Mb RAM
> PIII 800Mhz (8 speed steps)
> SIS 7018 Integrated sound chip
> Chipset mostly SIS I guess.
> 40Gb HD (Fujitsu, recent model)
> (Yea I know it's a piece of junk but I could write a heafty tome about my money situation at the moment)
> 
> Software
> --------
> Win2K NTFS 20Gb
> NTFS 10Gb
> Fedora Core 2 + CCRMA (everything from rpms), CCRMA Low latency kernal latest stable (2.6) ext2 10Gb
> Rosegarden4-1, built from source
> 
> Hokay,
> 1) I boot up the low latency kernal everything is fine until I run a midi app. 
> The machine has no physical ports but presents an input port and 5 output ports 
> in Qjackctl (SIS7018,trident driver). I think the first is raw, then Midi0-3. 
> The clearest repeatable falut I can give is when I run Qjackctl, with jack 
> either running or not running and try to connect to one of the SIS midi ports, 
> the machine freezes when I connect (Caps lock does nothing). 

Probably an alsa driver problem for your particular card. Check to see
(just in case) if there is anything related to the hang in
/var/log/messages. 

> 3) Should I be building all my own software for i686 ? Most of the CCRMA 
> stuff is i386 I can't remember at which point the 'big change' in intel 
> architecture happend (was it 286 got protected mode or somthing). Anyone 
> give me a ball park performace improvment percentage for rebuilding the 
> music software ? 

Probably 0% in most cases. While the binaries in Planet CCRMA are
compiled using the instruction set of the i386, the instruction
_ordering_ is optimized for the i686 architecture (same as the rest of
Fedora Core packages). In modern Intel processors the lack of the i686
instructions does not really impact performance. The ordering of
instructions, on the other hand, does have an impact on Intel
processors. AMD processors do their own instruction reordering so that
that does not matter either (in practical terms, I don't know if maybe
things would be 1% faster, which would not matter in the real world,
IMHO). 

I do build some things i386/i686 but I have never been able to measure
any significant difference in speed (not that I have tried very hard). 

This topic resurfaces every once in a while in the Fedora lists and the
answer from the gurus is always "give us feedback with performance
numbers and the improvement" (from compiling a given pacakge i686 _with
everything else the same_) and so far I have seen no numbers (that I
remember). 

-- Fernando




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