From: dalke@uxa.cso.uiuc.edu (dalke andrew)
Subject: Re: Z-150 PC HD type?
Summary: The author discusses some old Zenith computers
Organization: University of Illinois at Urbana
Date: Mon, 25 Jan 1993 10:20:59 GMT

In the referenced article mcg2@ns1.cc.lehigh.edu (Marc Gabriel) writes
about Z-150 PCs:
>Does anyone remember what kind of hard drive the old Z-150 PCs used?  Was it
>an MFM?  RLL?  Proprietary format?  The manuals say it is called a
>"Winchester" drive, but of course this means nothing in the real world.
>
>Sorry that I have to revive ancient history.  Any help would be appreciated.

  First off, ancient?  I'm running on a H-151 PC at 4.77 MHz.  Not
only is it a Zenith computer but it was distributed by Heathkit so
you could assemble it yourself (or I could) for $200 less.  Okay, so
a memory delay line died and I wore out the original A: drive - that's
_all_ that's gone bad in terms of hardware.  How many 486-50's will say
that in ten years?

  Okay, now that that's over.  I didn't actually get the HD with the 151.
(I had to wait about three years for that - but I was happy since I had
floppies instead of tapes!)  When I did, it was a Seagate.  Hopefully
the following will be of help.

Product information, Seagate drive, (c) 1987

ST412 Interface drives using MFM encoding at 5 MB / sec
	MB	# heads		cyl.
ST125	21	4		615
ST138	32	6		615
ST225	21	4		615
ST251	42	6		820
ST251-1	42	6		820
ST4038	31	5		733
ST4051	42	5		977
ST4053	44	5		1024
ST4096	80	9		1024

ST412 Interface Drives using RLL (2.7) encoding at 7.5 MB /sec
ST138R	32	4		615
ST157R	49	6		615
ST238R	31	4		615
ST251R	43	4		820
ST277R	65	6		820
ST4144R	122	9		1024

SCSI is listed also, but I doubt that that is what you have.

   Now for my problems.  I recently traded some RS-232 cable for
a CPU/memory board and a CGA/floppy card.

   The CPU worked once and raised my Norton SI form 1.0 to 1.6 so
I assume that it is 4.77/6 MHz board (there is a switch on the back).
(The crystals are 14.31.. MHz (=3*4.77) and 24 MHz(=4*6=3*8).
After a bit, the computer started complaining about memory
problems.  The ROM debugger pointed out a bad chip at U208.  I
swapped it with U209 and the computer would not boot.  It complained
about a hardware parity error in 0000:0000.  I "un-swapped" the
chips and it still would not work.  My old CPU does boot but
when I run its ROM debugger it gives me the same error at 0000:0000.
I ran a sweep through all of RAM (on my old CPU) using RAMVIEW
and found a couple of possibly bad memory chips but they were up
in 5395:0a78 and 8392:8568.
   My concern then is this:  Could there be a memory conflict between
the old and the new boards?  In which case (and in any case) does
someone out there know what the DIP switch and jumper settings are
for this board?  Also, could the jump in speed affect the older
(and slower) RAM on my Memory board?  The chips are numbered 
MT4264-15 for the US made ones, M3764-15RS from OKI Japan, and
SN74LS368AN for the TI chips from Malaysia.  There are a lot of
them (16k chips, remember them?)
   The board is a CPU/MEMORY BOARD 85-3162-01 111485 and the BIOS
is dated (c) 1984.

   My other acquisition is a CGA/floppy disk controller card.  The
CGA works well enough for me to see the error message that something
is wrong at the F000:0000 block of RAM.  Again, there are a lot 
of DIP switches so something might be mis-switched.  The
thing that gets me is that F000 is dedicated to ROM (according to
my copy of Norton's Programmer's Guide) so the new card should
not affect RAM check in that area at all.  The guy I got it from
says he didn't have any problem with booting up.  The problem
was that the disk controller would not work.  The card is simply
labeled ZENITH DATA SYSTEMS COLOR VIDEO/FLOPPY BOARD and the
last date I see on it is 1986.  If I can get it working, I can
take out the other two boards (keeping them as backups, of course)
and have a free slot!

  If anyone can offer any suggestions or meanings behind DIP 
and jumper settings, I would love to hear from you.

					Andrew Dalke
					dalke@uxa.cso.uiuc.edu
.plan
-- 
					Andrew
					dalke@uiuc.edu