Date   : Fri, 29 Jul 1988 01:24:32 GMT
From   : eve.usc.edu!mlinar@oberon.usc.edu (Mitch Mlinar)
Subject: Need help with brain-damaged bdos.

In article <187@lakart.UUCP> dg@lakart.UUCP (David Goodenough) writes:
#From article <9936@e.ms.uky.edu#, by simon@ms.uky.edu (George Simon):
##     The version of cpm that it is running seems to be < 2.2, and 
##     the bdos seem to be brain-damaged.
##
##     (2) Bdos function 6 (direct console i/o) does not exist, but 
##             the corresponding bios calls work ok.  Other bdos calls 
##             may be ok, but I trust the bios much more.  The bdos also
##             refuses to return the version#.
#              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
#
#This may be part of your problem: function 12 (0xc) in V2.0 and higher
#gives back the version number - V1.X does not: it appears that you have

True, but still usable as is.  In CP/M 1.3 and 1.4, it was not *intended* to
return the version number, but rather some obscure disk function like "unload
heads" or something like that.  The function *is* supposed to return A=00,
which lets you know it is earlier than CP/M 2.x or MP/M.

# ##   Anyone got any other ideas?  I'd love to be able to do double-density,
# ##   but I don't know if the WD1771 can do this.  I have heard that
#Sadly the 1771 only talks single density, and Idon't know if the 1791 /
#1793 would be a dropin replacement.

David is correct about the single-density 1771; also, the 1791/1793 is NOT a
drop in replacement.  You need a bit of external clock/data separation
circuitry to run double density as well as a higher clock rate to the chip
itself (2 MHz instead of 1 MHz).  Potentially some major board work here...

I missed out on the earlier conversation, so don't know what system you have
and if there is some adapter kit sold for your machine.

-Mitch


End of INFO-CPM Digest
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