From alsa-devel-owner@alsa.jcu.cz  Thu Jul 16 22:22:22 1998
Received: from altrade.nijmegen.inter.nl.net (altrade.nijmegen.inter.nl.net [193.67.237.6])
	by marvin.jcu.cz (8.8.8/8.8.8) with ESMTP id WAA13088
	for <alsa-devel@jcu.cz>; Thu, 16 Jul 1998 22:21:22 +0200
Received: from obelix.fvdpol.inter.nl.net by altrade.nijmegen.inter.nl.net
	via bd99-26.Breda.NL.net [193.79.246.251] with ESMTP for <alsa-devel@jcu.cz>
	id WAA21801 (8.8.8/3.28); Thu, 16 Jul 1998 22:21:20 +0200 (MET DST)
Received: (from frank@localhost) by obelix.fvdpol.inter.nl.net (8.8.7/8.7.3) id VAA26734 for alsa-devel@jcu.cz; Thu, 16 Jul 1998 21:55:03 +0200
From: Frank van de Pol <F.K.W.van.de.Pol@inter.nl.net>
Message-Id: <199807161955.VAA26734@obelix.fvdpol.inter.nl.net>
Subject: SoundBlaster IRQ (was:  Re: ALSA Sequencer)
To: alsa-devel@jcu.cz
Date: Thu, 16 Jul 1998 21:55:02 +0200 (MET DST)
In-Reply-To: <199807140957.LAA00387@algorythmics.mhsg.ac.at> from "Winfried Ritsch" at Jul 14, 98 11:57:28 am
Content-Type: text
Reply-To: alsa-devel@alsa.jcu.cz
Sender: alsa-devel-owner@alsa.jcu.cz
Precedence: list

Winfried Ritsch wrote:
> 
> > 
>  > Note: I have still trouble with MPU-401 UARTs and compatible (this
>  > includes all SB16/AWE soundcards). I don't know how can solve problem
>  > with polled transmit (this means that CPU must wait if some room is in
>  > transmit FIFO and after this send MIDI byte - no transmit interrupts are
>  > generated). Looks that SB AWE 64 have only room for 2 bytes in transmit
>  > FIFO!!! This is very small value and ALSA driver is able send with current

Is that REALLY so??? I can hardly imagine... If it's true that hardware is
very much broken, and I'm wondering how this is dealt with on all those MS
windows boxes. Soundblaster is _the_ standard on the Windows platform.
Perhaps there is some 'hidden' feature.

Does this problem also show up when the internal synth of a soundblaster is
used? Eg. playing sounds on the EMU synth? I'm asking because I am
considering buying one AWE64, and if it is that broken, I'd better spend my
money on other hardware.

> 
> a) The point is the scheduling intervall, which is for pentium computers
> very conservativ, since 10ms on a i386 30MHz works ok. 1 ms on a 100MHz
> is fine and 0.5ms on a 130 MHz wworks ok. I always run
> "pd" on my computer (a 100MHz Pentium Notebook) just with 1ms, so also
> reaction time to soundprecessing is reduced to 30ms instaed of 200ms.
> 
> I think 1ms has the alpha, so with 0.5ms there is no loss anymore.

For a 31.25kbps data rate on the MIDI buss you'll have to send one MIDI byte
every 0.3ms. Polling would have to be done at the same rate (slightly slower
than MIDI data rate to prevent synchronisation problems).

This whole concept is one big workaround. I'd better take a soldering iron
and add the IRQ line myself, or scrap the whole card... (or use it only for
output).

Regards,
Frank.

+---- --- -- -  -   -    - 
|Frank van de Pol                  -o)
|F.K.W.van.de.Pol@inter.NL.net     /\\
|                                 _\_v
|Linux - Why use Windows, since there is a door?
|
|ALSA Sequencer: http://www.inter.nl.net/users/F.K.W.van.de.Pol/alsa/

