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From: andrews%cpsc.calgary.CDN@ean.ubc.ca (Keith Andrews)
Newsgroups: comp.sys.zenith.z100
Subject: Re:  Memory and RamDisks on the Z100
Message-ID: <569*andrews@cpsc.calgary.cdn>
Date: 24 Mar 88 17:41:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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Gern's assessment on the problems with using the high order address latch
to get at the upper 15Mbytes addressable on a Z100 is quite correct.
However, if you have a Z217 board (hard disk controller) or equivalent
in your system, you can use it to simply DMA (sorry TMA) the initial
code into high memory. (whoever designed the Z217 should be commended:
it does everything just like the ones in "real" [:-)] computers - which
is more than you can say about the glorified floppy disk controller in
IBM PCs.)

Speaking of the Z217,  the technical manual that comes with it gives some of
the controller command and reply codes. However, there seems to be a few
missing command codes.  As evidence, the command and reply codes are grouped
according to function: (this is from memory, the details are probably wrong)
the 0X functions have to do with head motion (seek/restore), 1X are read
functions, 2X are write functions and 3X are format functions.  The manual
also lists some 4X reply codes which have to do with diagnostics but there
aren't any 4X command codes.  Furthermore, there are holes within each
fuction group (e.g. there'd be a 31 and 33 command code, but no 32).  Does
anybody know if there really are undocumented commands and what they might
be?

						Keith Andrews
				     andrews%cpsc.calgary.cdn@ean.ubc.ca