Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!dasys1!eravin
From: eravin@dasys1.UUCP (Ed Ravin)
Newsgroups: comp.sys.cbm
Subject: Re: Zmodem implementations
Summary: RS-232 and disk I/O cannot mix
Keywords: RS-232 IEEE-488 FROG BBS
Message-ID: <9012@dasys1.UUCP>
Date: 15 Mar 89 18:13:41 GMT
References: <1786.2416BB83@isishq.FIDONET.ORG> <7509@killer.Dallas.TX.US>
Reply-To: eravin@dasys1.UUCP (Ed Ravin)
Organization: Unix Police
Lines: 33

In article <7509@killer.Dallas.TX.US> elg@killer.Dallas.TX.US (Eric Green)
writes:

>I wouldn't be so saguine about the perfection of simultaneous IEEE-488
>and RS-232. I have tried out both the C-Link II and IEEE Flash and
>found that if you do not disable the RS232 NMIs before doing disk I/O,
>you will occasionally get a garbled character from the disk.
>Especially bad was the case where incoming RS232 would corrupt writes
>to the disk -- I lost several internal BBS file directories to that
>problem...

>I suspect that the situation would be a lot better with a good IEEE
>interface (e.g. the Buscard II or the original SKyles Quicksilver),
>but still wouldn't trust it. 

I wouldn't trust it either.  When me and a friend developed the FROG-BBS,
a C64 BBS program, one of the devices we supported was the Buscard II.  We
had exactly this problem: RS-232 NMI's would scramble data being read from
the disk, which would eventually cause us to crash when critical data (such
as pointers to messages) became garbled.  We ended up re-inserting the RS-232
holdoff the Kernal usually has for these situations into our own software.

Otherwise, the Buscard II was just wonderful, thought it wasn't quite as
fast as the IEEE-488 interface that MSD provided.  The MSD interface had
other problems, though, including needing a SYS call to be activated (yuk)
and taking up 2k or so of memory away from BASIC (big YUK, since our BBS
program needs all the memory it can get and then some).

-- 
Ed Ravin                  | cucard!dasys1!eravin | "A mind is a terrible thing
(BigElectricCatPublicUNIX)| eravin@dasys1.UUCP   | to waste-- boycott TV!"
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