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From: dyer@spdcc.UUCP
Newsgroups: net.music.synth,net.micro.pc
Subject: Roland MPU 401 MIDI i/f, PC/AT and INT 2
Message-ID: <352@spdcc.UUCP>
Date: Sun, 13-Jul-86 18:32:14 EDT
Article-I.D.: spdcc.352
Posted: Sun Jul 13 18:32:14 1986
Date-Received: Sun, 13-Jul-86 22:24:12 EDT
Organization: S.P. Dyer Computer Consulting, Cambridge MA
Lines: 17
Xref: utcs net.music.synth:1375 net.micro.pc:8999

The issue of hardware interrupts on the PC/AT and compatibility with
boards originally designed for the PC reads its ugly head once again.
The MPU401 generates an interrupt on INT 2, which is used in the AT
as a cascade for a second interrupt controller.  Actually, it *seems*
to work in my AT, perhaps because the software might do some interrupt
shuffling (this is only a guess.)

My question is: is there any harm in having two devices share the same 
hardware interrupt level, provided that the interrupt routine manages
to disambiguate between the originating devices?  How about INT 2, which
I believe is used for hard disk interrupts? 

P.S.: anyone know the IO port addresses of the Roland?
-- 
Steve Dyer
dyer@harvard.HARVARD.EDU
{linus,wanginst,bbncca,bbnccv,harvard,ima,ihnp4}!spdcc!dyer