Path: utzoo!utgpu!watmath!isishq!f171.n221.z1.FIDONET.ORG!izot
From: izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh)
Newsgroups: comp.sys.cbm
Subject: Bursting C64 (WAS: Simultaneous disk & RS-232 access)
Message-ID: <1576.23F37833@isishq.FIDONET.ORG>
Date: 7 Feb 89 23:06:25 GMT
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 > From: eravin@dasys1.UUCP (Ed Ravin)
 > Message-ID: <8611@dasys1.UUCP>
 >
 > Hmmm.  Now I really should go home and read my 128 PRG again before putting
 > my electronic foot in my mouth, but the 128 doesn't have an external CIA or
 > any extra hardware for burst mode, does it?
 
   The C128's internal serial port hardware is actually very different from 
the C64's. As you say later in the message, various CIA lines are connected to 
the serial port but that meant that the C128 firmware had to do various extra 
data direction register settings to prevent conflict whenever it used the 
serial port. Since the C64 ROMs in the C128 are untouched, the MMU actually 
physically disconnects these when in C64 mode!
 
   Bottom line: even if you added the hardware connections to a C64 and did 
the software to avoid conflicts, it wouldn't work in C64 mode on a C128.
 
   Interestingly enough, there was one prototype BusCard III built by Jim Law 
& Steve Douglas (the same ones who did the BusCard II for Batteries 
Included)... it included IEEE-488 AND fast (burst) serial ports, plus most of 
BASIC 4.0 (not quite as complete as the version in the BC II, but including 
many useful disk commands). Unfortunately, by the time the prototype was done, 
there weren't any companies interested in producing the product and Steve & 
Jim didn't want to waste any time on it if it wasn't going to go anywhere.
 
   Geoff ( watmath!isishq!izot )
 


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