Re: PET / cbm2 timing questions...

From: André Fachat <>
Date: Mon, 20 Dec 2010 22:36:43 +0100
Message-ID: <>
>What I have observed though is that the "high level" disk commands on the
>CBM-II machines freezes the IEEE chain. That means CATALOG D0 fails while
>LOAD"0:$",8 is OK. On the PET machines, both work equally well.

The internal code is actually indeed different between the DOS4 and
the DOS2 commands.

LOAD"0:$",8 actually reads a file in one go, i.e. 
send: TALK
receive: all file data until EOF
send: UNTALK
(not sure about the close though)

CATALOG or DIRECTORY on the other hand reads the $ file in parts.
I.e. IIRC after each line the computer sends an UNTALK, and then,
after processing (displaying) the line, sends another TALK to continue.
I had to work around this on my IEEE drive emulations...

But that is for the PET. My assumption is that it is the same for the
CBM-II though.

In the PET I had to patch the IEEE routines to work on higher CPU speeds
(when using the PET ROMs in my CS/A computer at 2MHz). The symptom IIRC was
that between sending the file name and sending the TALK to receive
the data the computer became too fast. But it would give an error message
on LOAD"$",8 but would not hang.

What other commands have this problem? Can you patch the IEEE code? Then 
you could problem try to port the patch here
to the CBM-II and try it.


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Received on 2010-12-20 22:00:46

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