Lifeline Z-100 User manual

2022
March 2022
#WEB
Note: This article was originally published in issue #59, October 1998.
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Z-100 MFM Hard Drives
PRELIMINARY INFORMATION:
With the proliferation of older computers at
swap meets and electronics surplus houses, now
is a good time to upgrade your Z-100 with a
second hard drive, or if you don't have any yet,
replacing one of the floppy drives in your
machine with a hard drive, though some special
circuit boards are needed.
Since the first 5, 10, or 12 meg hard drives
(called Winchester Drives by Heath/Zenith were
placed in the Z-100 in the mid-80s, there have
been several types developed - MFM, RLL, SCSI,
IDE and others. The drives usually found in the
Z-100 were the first type - MFM - and the sub-
ject of this article. For more information on
the other types of hard drives, I have attached
the article, “Driving Us Crazy, But For a
Reason”, by Alan Brenden at the end of this
article.
Another drive type - SCSI - with considerably
larger capacities, became available for the
Z-100 in the late 80s with a SCSI Controller
marketed by CDR. Paul Herman, editor and
publisher of the “Z-100 LifeLine” at the time,
tried to get a special order of boards from CDR
adapted specifically for the Z-100. However, it
soon became evident to Paul, and several
volunteers working as his staff, that they
needed to develop their own controller, and the
new Z-100 LifeLine SCSI/EEPROM board was
created.
As the MFM and newer SCSI systems became more
scarce, attention turned to the newer IDE
technology and another group of volunteers; John
Beyers, Charles Hett, and I. We researched and
developed the new Z-100 LifeLine IDE NvsRAM
board, shipped in late 2008.
You can find additional information on these
newer systems elsewhere on this site. This
article will concentrate on the use of the
initial Winchester hard drive.
The Heathkit/Zenith MFM hard drive installation
was comprised of a Z-217 Winchester Controller
Card in the card cage, a separate, unique Data
Separator Board that was normally mounted near
or over the hard drive and the MFM hard drive
itself. These pictures show the drive tower
configuration possible for the Z-120 All-In-One
Computer ==>
1

Other hard drive kits were available, but were
less popular and therefore less available now.
Note: Be sure your computer operates properly
BEFORE you begin the following modifications. If
your Monitor Rom is a version prior to 2.5,
you'll probably need to upgrade some parts on
the motherboard, including the Monitor Rom
(U190). If your motherboard is the old version,
85-2653, some circuit modifications may also be
needed. See the following text.
Note: The term 'Z-100' in this article and
others published in the "Z-100 LifeLine" refers
to the class of Heathkit/Zenith computer and may
apply to either the Low-Profile H/Z-110 model,
which used a separate monitor, or All-in-One
H/Z-120 model, where a monochrome monitor was
self-contained.
The MFM ‘Winchester’ Hard Drive:
The following instructions cover installation in
both models of the Z-100 computer. The diagrams
will carefully show which model applies, when
necessary.
Important: Early MFM hard drives are fragile and
can be damaged easily. In all hard drives, while
the drive’s platter is spinning, the read/write
heads float on a very thin layer of air, sep-
arating the heads from the platter’s surface.
However, the read/write heads on these early
drives came to rest on the surface of the disk
platter when rotation stopped. Any bumping,
knocking, or dropping may cause the heads to
bang against the surface of the platter. A
severe bump, especially while the platter is
spinning, could actually damage or gouge out a
small area in the platter and cause a “crash”,
where an important portion of a program is
unreadable and lost because the disk surface was
damaged. Further, the read/write head may also
be damaged.
For early hard drives, it is CRITICAL to run a
disk utility that parks the heads in an unused
portion of the disk - a storage or parking area
- before the heads come to rest. Such a utility
is SHIP, an external command packaged in CP/M
and MS-DOS operating systems. Later MFM drives
had an auto-park feature that placed the heads
down after the last usable sector of the drive,
in an unused area. But even then, the heads
could be damaged from a sudden drop.
MFM drives are recognized by their two ribbon
cable card edge connectors, one with 34 con-
ductors and the other with 20 conductors. RLL
drives also have these but the drive model
number includes an R. For example, an ST-138 is
an MFM drive, while an ST-138R is an RLL drive,
with different formatting, capacities, and
controller boards. ESDI drives also have similar
cable connections, but cannot be used.
MFM drives are becoming available from Ebay and
the used market, sometimes at ridiculous prices
and there is no guarantee that any of these will
work.
But let’s assume that you find one with possi-
bilities and want to try it. What is involved?
Caution: You cannot just slap an MFM drive from
another computer into your Z-100 and expect it
to work, without completely reformatting the
drive. It will require low level formatting
using the Z-100 PREP command, partitioning using
the PART command, and a high level formatting of
each partition using the FORMAT command. These
commands are unique to the Heath/Zenith CP/M and
MS-DOS (now referred to as Z-DOS) operating
systems.
There are numerous manufacturers of MFM drives,
each with different sets of programming plugs,
jumpers, and terminating resistors. If you have
a specific brand that you can not figure out,
try emailing me at the “Z-100 LifeLine”.
2

Here are views of my hard drive setup on my test
bed Z-100 (note the cabling):
The Hard drive here is the Disctron D-514.
Here are a few installation precautions:
* Try to install the new drive alone and boot
to a floppy to run the Winchester Disk Util-
ities. It can be run from another hard drive,
but you would hate to accidently PREP the wrong
drive!
* If the new drive is installed alone, insure
the terminating resistor pack is installed. If
it is the second drive, only install the term-
inator resistor on the hard drive installed last
on the 34-pin connector ribbon.
* Double check that the ribbon cables are
installed per the directions given later. Insure
all connectors are fully seated and that pin one
of each ribbon connector (the ribbon cable may
also have a red edge) is at the correct end of
the connectors on the drive, controller, and
data separator. The 20-pin cable connector can
go to either location on the Data Separator
Card.
* Before running PREP on a hard drive, you must
install the Format Enable Jumper on the Z-217
Controller Card. It is located under the power
connector in the upper left corner of the Z-217
Hard Drive Controller, and may be stored any
where along the top row of pins of the VI*
jumpers, when not in use. See the Software
Programming section for more on this.
* Check for a programming plug on the new drive
before installation and make a note of the
position of any jumpers. Try this setting first
and if unsuccessful, try the other positions
before giving up.
Hint: Drive Select (DS) pins may be labeled DS0
through DS3 or DS1 through DS4, if labeled at
all. If this is the lone drive, DS0 (or DS1)
will become drive unit 0 and after programming,
drive E:.
Hint: Before changing any positions on the
programming plug, install the hard drive
temporarily, boot up the computer, and run
ASGNPART 0:. If the drive is already setup as
drive 0: the drive LED should light. If it does
not, check ASGNPART 1: and even 2: and 3: before
giving up. If the LED will not light in any
position, check the cables for an improper
connection and finally try a different position
on the programming plug.
Note: If partition info is displayed after
running ASGNPART, do not proceed with PREP until
you have tried other options. For example:
- Try running ASGNPART X:(Partition name) E:,
where X: is the drive unit number. Then do a
directory listing on E:.
- Try running DETECT or VERIFY to see how many
bad sectors are found.
- Try reformatting the partition with FORMAT to
isolate those bad sectors.
3

MFM Hard Drive Installation
DISASSEMBLY:
Installation of a hard drive requires partial
disassembly of your computer. As disassembly and
reassembly are beyond the scope of this article,
please refer to your Z-100 Users' Manual or the
‘About Z-100 Computer’ on this website for these
procedures.
Caution: In the All-In-One Computer, high
voltages are present around the large wire
attached to the top of the picture tube.
For the Z-110 Low-Profile Computer, remove the
cover and drive assembly. For the Z-120 All-In-
One Computer, remove the cover and the CRT/drive
assembly. Set these aside.
From here down internally, both models are the
same. The card cage, with its removable vertical
boards, such as the Z-205 RAM Board or Floppy
Controller Board, is to the rear of the compu-
ter. A large motherboard fills nearly 3/4 of the
computer's bottom with a much smaller video
logic board mounted horizontally on 3 standoffs
on the motherboard.
One or two smaller boards, such as a Gemini
PC-Emulator Board or an 8087 co-processor board,
may be sandwiched between the two.
Before attempting to install a hard drive in a
Z-100 computer, ensure that the power supply has
the proper cables for the Data Separator and the
Z-217 Winchester Controller Boards. These may be
folded up and stored to the side.
Figure 1.
Power Supply Connectors
Also ensure the proper PAL and ROM integrated
circuits are installed, using the following
procedures:
Caution: Refer to the Z-100 Users' Manual for
the proper procedures on handling integrated
circuits (ICs). Many ICs are metal oxide semi-
conductors (MOS) which can be damaged by static
electricity.
[ ] Remove the three small screws attaching
the video logic board horizontally across the
motherboard and swing it upward onto its back
edge (carefully lean it against the card cage).
Note: Read the following steps carefully. You
may already have the correct ICs installed in
your motherboard.
[ ] Locate the PAL IC (U161) on the mother-
board. If the part number on this IC is lower
than 444-129-1 (such as 444-129), the IC must be
replaced before installing a hard drive.
[ ] Locate the Monitor ROM (MTR-ROM or ZROM)
IC (U190) on the motherboard. If the part number
on this IC is lower than 444-87-5 (such as 444-
87, 444-87-1, -2, -3, or -4), the IC must be
replaced before installing a hard drive.
Note: Newer power supplies, hard drive boards,
PALs and ROM chips are available from the "Z-100
LifeLine".
[ ] If you are installing a ZROM v3.x monitor
ROM (or later) at U190, locate the programming
jumper J102 on the left edge of the motherboard,
about half way from the front to the card cage.
Unplug it from the 0 position and reinstall it
in the 1 position, if this has not already been
done. This jumper recognizes the higher capacity
of the newer ROM chip. Be careful not to disturb
the setting of programming jumper J101.
[ ] Locate switch S101 on the motherboard and
set each switch to the 0 position (toward the
card cage or rear of the computer), if this has
not already been done.
Note: Section 7 of this switch sets the refresh
rate of the display RAM and is normally set to
the zero position for 60 Hz (in the U.S.). If
you live overseas and your AC line frequency is
50 Hz, you must set this switch section to 1.
[ ] Locate the part number on the motherboard
(near U190). If this part number is 85-2653
(disregard any other number that may follow,
such as 85-2653-1), you have an older mother-
board that will require several modifications.
These modifications are available from the
"Z-100 LifeLine", but involve soldering on the
board.
Note: The "Z-100 LifeLine" has plenty of the
newer motherboards at reasonable prices (See the
pricelist on the “For Sale” page of the Website.
[ ] Reinstall the Video Logic Circuit Board on
its three standoffs and secure it with the three
screws.
PREPARING THE MFM HARD DRIVE:
Note: While the hard drive may be installed
first, I find it is best to prepare the hard
drive and ensure it is working properly BEFORE
taking the time to install it. Earlier, I showed
two pictures showing how the hard drive may be
placed temporarily on the power supply during
preparation.
4

The PREP and PART utilities were available on a
special disk entitled ‘Winchester Utilities
Disk’, distributed separately from the earlier
MS-DOS versions. The disk and instructions are
available from the “Z-100 LifeLine” Library.
Caution: Using PREP is the last resort. It will
destroy all the files that may exist on the hard
drive. If the disk is from another Z-100, you
may need to use PREP only if you consistently
encounter an unreasonable number of disk access
errors. Do NOT use PREP until you have backed up
all important files you wish to keep to floppy
disks.
PREP has been updated by John Beyers in the
Z-100's Z-DOS v4 that allows it to be much more
flexible in its operation - another reason to
upgrade.
All versions of the PREP utility enable you to:
* Initialize the surface of the hard disk.
* Test the data retention capabilities of the
hard disk.
* Isolate questionable disk sectors.
* Divide the surface of the hard disk into 2
partitions (Z-DOS and CP/M).
PREP takes a long time to run. Expect it to take
about 1.5 hours for every 10 megabytes in hard
drive size. It runs seven surface passes to
check the media and locate bad sectors. These
locations are placed in a Bad Sector Table and
can no longer be used.
Note: With the version 4 PREP, you can set the
number of passes to make.
If the hard disk does not contain initialization
information (from a prior PREP operation), PREP
will prompt you to enter characteristics (in
hex) in order to identify the type of hard drive
that is being installed in the computer.
Please see the file MFMHardDriveSpecs.PDF on the
Website for a list of common drives that were
used in the Z-100. I have updated this infor-
mation for many more manufacturers.
Note: Several of the drives are too large for
normal use in the Z-100. Early hard drives and
Z-DOS versions in the Z-100 were limited to
32Mb. Later, with the addition of the PREP /k
switch (which uses 1024 byte sectors rather than
512 byte sectors), the limit was extended to
64Mb. As I understand it, Z-DOS version 4 can go
higher, though I do not recall the limit. Just
remember, larger than 64Mb will ONLY work with
Z-DOS v4. To be able to use these larger hard
drives, the fix is easy - just reduce the number
of heads being used by PREP until the number of
megabytes is where you want it.
Once PREP has completed, if you run ASGNPART 0:
you will see the two partitions created: Z-DOS
and CP/M. If you are satisfied with these two
partitions, you will not need to repartition the
disk with PART.
However, if you wish to change this partition
information, you must run the PART utility.
The PART utility is self explanatory. Just
follow the procedures as given to change the
partition names and sizes as necessary, then
choose a default boot partition and save the
configuration to the hard drive.
When complete, you may need to reboot the
computer to the floppy drive again.
Next run ASGNPART 0: to confirm the partitions
are as you required.
Before we can use the new partitions, you need
to assign drive letters to them and then run
FORMAT to do a high level format of each new
partition. Run ASGNPART 0:(partition name) E: to
assign the drive letter E: to the first
partition. Likewise, assign succeeding drive
letters (F:, G:, H:) to the remaining new
partitions (up to four at a time). Run FORMAT
X:/s/v to format and load the system files on
each new partition, where X: can be E:, F:, G:,
or H:.
If successful, you are now in business. Email me
if you have any difficulty. I hope this helps
clarify the use of Z-100 MFM hard drives.
Important: Hard drives, especially these early
MFM hard drives are fragile and can be damaged
easily.
In all hard drives, while the drive's platter is
spinning, the read/write heads float on a very
thin layer of air separating the heads from the
platter's surface. However, when stopped, the
heads come to rest gently on the surface of the
disk platter.
Any bumping, knocking, or dropping causes the
heads to bang against the surface of the plat-
ter. A severe bump, especially while the platter
is spinning, could actually damage or gouge out
a small area in the platter and cause a "crash",
where an important portion of a program is
unreadable and lost because the disk surface was
damaged.
For early hard drives, it is CRITICAL to run a
disk utility that parks the heads in an unused
portion of the disk - a storage or parking area
- before the heads come to rest. Such a utility
is SHIP, an external command packaged in CP/M
and early MS-DOS operating systems.
Later disk drives have an autopark feature that
automatically parks the heads upon power loss.
This article concentrates on MFM drives, which
used the standard hard drive boards found in
most Z-100 computers. MFM drives are recognized
by their two ribbon cable card edge connectors,
one with 34 conductors and the other with 20
conductors.
RLL drives also have these but the drive model
includes an R. For example, an ST-138 is an MFM
drive, while an ST-138R is an RLL drive, with
5

different formatting, capacities, and controller
boards.
The same number drive may even have a different
number of heads or cylinders. So, to my know-
ledge, there is no way to change a RLL drive
into an MFM drive by just swapping boards
attached to the drive.
ESDI drives also have similar cable connections
and cannot be used, but these drives are rare.
While new MFM hard drives are very rare now,
some remanufactured or repaired hard drives can
still be purchased from drive repair shops.
Also, look for older computers at garage sales,
shops, swap meets, etc.
Caution: You cannot just slap an MFM drive from
another computer into your Z-100 and expect it
to work, without completely reformatting the
drive. It will require low level formatting
using the PREP command, partitioning using the
PART command, and a high level formatting of
each partition using the FORMAT command. These
commands are unique to the Heath/Zenith CP/M and
MS-DOS operating systems.
There are numerous manufacturers of MFM drives,
each with different sets of programming plugs,
jumpers, and terminating resistors. If you have
a specific brand that you can not figure out,
try calling me at the "Z-100 LifeLine".
PROGRAMMING PLUGS:
The most popular drive in the Z-100 seems to be
the 10 megabyte Miniscribe model 2012 pictured
here:
Figure 2.
Programming Plug on the Miniscribe 2012.
Other popular drives were the 10 meg Seagate
model ST-412 and the 10 meg Computer Memories,
Inc. model CM 5412. These were all full height,
5-1/4" drives. Later drives were available as
half-height and/or 3.5" wide and had higher
capacities.
[ ] Locate and check the setting of any
programming plugs or pins on the hard drive.
Programming plugs may take many forms on floppy
and hard drives. On the Miniscribe 2012 and the
Seagate ST-412, it takes the form of that shown
in the picture - a flat pack of 8 shorted pairs
of pins. Although meant to simply break the
connection between pairs with a sharp pointed
object, a less permanent method is to simply
bend out one of the pins to open that pair, as
shown.
On the Miniscribe 2012, the drive configuration
is:
Pin Sect Hardware Unit
Pair Nbr: Note 1 2
1-16 1 Open Open
2-15 2 Short Short
3-14 3 Factory Set
4-13 4 Factory Set
5-12 5 DS4 Open Open
6-11 6 DS3 Open Open
7-10 7 DS2 Open Short
8- 9 8 DS1 Short Open
Note: Pin pairs 3-14 and 4-13 (section 3 and 4)
are set at the factory; the programming plug is
properly configured for the drive it is instal-
led in. If you change or move programming plugs,
you should check the following table and set
these two sections according to the phase code
of the disk drive. The phase code is printed on
a label on the disk drive case.
Pin Pair: 3-14 4-13
Section Number: 3 4
----------------------------------------
Phase Code C Open Open
Phase Code D Open Short
Phase Code E Short Open
Phase Code F Short Short
----------------------------------------
On the Seagate, the programming information is
slightly different:
Pin Sect Hardware Unit
Pair Nbr: Note 1 2
1-16 1 R Short Short
2-15 2 NC Open Open
3-14 3 NC Open Open
4-13 4 NC Open Open
5-12 5 DS4 Open Open
6-11 6 DS3 Open Open
7-10 7 DS2 Open Closed
8- 9 8 DS1 Closed Open
Where: DS1, DS2, DS3, DS4 = Drive Select
#
R = Radial Operation
6

PROGRAMMING TIPS:
How should my strange drive be
configured? How can I program a drive
if it doesn't have a programming plug?
- A great temporary programming plug
can be a dip switch with the proper
number of sections.
- The drive number may begin at one
end or the other of the plug or row of
jumper pins. Leaving the other pins
open, short one end or the other and
start the computer. If the light
flashes as the computer attempts to
boot, you have the drive select pins
identified. Odds are, the first four
pairs of pins are the drive select
sections for 4 drives, working from
the outside toward the center.
- After finding the drive select pins,
attempt to program the drive with no
other switches/pins shorted. If an
error develops, short a pair of pins
and try again.
On the Computer Memories drive, the programming
is accomplished by pairs of pins and removable
jumper plugs. DS1 is the pair of pins closest to
the front of the drive, with DS2, DS3, and DS4,
in order, toward the rear of the drive.
I have no information on the remaining two pairs
of pins.
TERMINAL RESISTOR PACK:
Looking at the Miniscribe picture again, you can
also see the location of a Terminator Pack or
Terminal Resistor Pack. This resistor pack
serves the same purpose as on the floppy drives
and needs to be installed ONLY in the drive at
the end of the 34-conductor ribbon cable.
[ ] If this is your only hard drive, leave the
resistor pack installed. If this hard drive will
be an external drive, of a pair of hard drives,
install the resistor pack only on the last hard
drive on the 34-pin connector.
[ ] If the hard drive is replacing one of the
floppy drives, ensure the remaining floppy drive
has a terminal resistor pack and the drive
select is properly set, DS0 or DS1, as needed.
As with the floppy drives, it is the drive
select position on the programming plug that
determines the drive number or letter and it
doesn't matter if the first drive letter is
first or last on the cable. Therefore, drive 0
(E:) of a two drive system can be first or last
on the ribbon cable. It is always the last drive
on the ribbon cable that has the terminator
resistor installed.
MOTHERBOARD DIP SWITCH:
After the initial testing and programming of the
hard drive, the computer can be set to auto boot
from the hard drive by changing the positions of
switch S101, Figure 3.
Note: The positions 1 and 0 are not labeled on
all motherboards. The position 1 is always
toward the front of the computer, 0 is toward
the card cage.
Switch sections 0, 1, and 2 select the type of
drive that the system will boot from:
Section: Device
0 1 2 Type:
0 0 0 5-1/4" Floppy Drive
1 0 0 8" Floppy Disk Drive
0 1 0 Winchester Hard Drive
1 1 0 SCSI/EEPROM Board
And Switch section 3 selects Auto or Manual
Boot, where:
1 = Auto boot
0 = Manual boot
Figure 3.
Switch S101 on the Motherboard
INSTALLING THE HARDWARE:
[ ] Both computer models require the Z-217
Winchester Controller Board be inserted in any
free slot of the Card Cage at the rear of the
computer. See Figure 4. Note the position of the
large connector for the 4-pin power supply cable
on the left.
[ ] Installation of the hard drive in the All-
In-One Z-100 is shown in Figure 5. It involves
mounting the hard drive in the upper or lower
bay of the drive chassis, depending upon the
type of faceplate you have available.
If your hard drive has its own faceplate, you
may be able to cut a large opening in your
existing faceplate.
7

Figure 4.
Inserting Z-217 Controller Card
[ ] The Data Separator Circuit Board is
mounted on the top of the drive chassis with two
brackets.
Figure 5.
Data Separator Board
All-In-One Computer
[ ] Installation of the hard drive in the Low-
Profile Z-100 is shown in Figure 6. The hard
drive is mounted in the left bay of the drive
chassis. The drive will need a pair of mounting
brackets for the full height drives, but if you
already use half height floppy drives, the same
brackets could be used to mount a half height
hard drive. The Data Separator Board is mounted
over the drive.
If your hard drive has its own faceplate, you
may be able to cut a large opening in your
existing faceplate.
Figure 6.
Data Separator Board
Low-Profile Computer
CABLE CONNECTIONS:
Figure 7 shows the various cable connections on
the rear of an MFM hard drive.
Figure 7.
Hard Drive Cables
8

Figures 8 and 9 show the cable positioning in
the All-In-One Computer.
Figure 8.
Ribbon Cables
All-In-One Computer
Figure 9.
Power Supply Connectors
All-In-One Computer
9

Figures 10 and 11 show the cable positioning for
the Low-Profile Computer.
Figure 10.
Figure 11.
10

[ ] A 34-conductor cable goes from the Data
Separator Board to the right 34-pin connector on
the Z-217 Controller Board in the card cage. At
both ends, the marked edge of the cable is
positioned toward the power supply connector.
[ ] A 20-conductor cable goes from either 20-
pin connector on the Data Separator Board to the
20-pin edge connector at the rear of the hard
drive. At both ends, the marked edge of the
cable is positioned toward the power supply.
[ ] The last 34-conductor cable goes from the
left 34-pin connector on the Z-217 Controller
Board in the Card Cage to the 34-pin edge
connector at the rear of the hard drive. At both
ends, the marked edge of the cable is positioned
toward the power supply.
[ ] Connect the large 4-pin power supply
connector to the Z-217 Winchester Controller
Board.
[ ] Connect the 3-pin power supply connector
to the Data Separator Board.
[ ] Connect the smaller 4-pin power supply
drive connector to the hard drive. The Mini-
scribe Model 2012 is perfect for the Z-100
because of the extended pigtail drive connector.
Drives from other manufacturers just have a
connector on the rear of the drive. Still
usable, but less convenient.
Figure 12.
Exterior Hard Drive Cabling
Figure 12 shows the suggested cabling for adding
a second, external hard drive. Note the position
of the backplane connectors allows the addition
of the drive without disturbing the internal
drive's position as last on the cable. This
interior drive therefore keeps the terminal
resistor whether the external drive is connected
or not! Do not use a terminal resistor in the
external hard drive.
[ ] Reassemble the computer using the assembly
instructions in the Users' Manual. Do not yet
install the cover, as some low level programming
of the hard drive is required and discussed
next.
SOFTWARE PROGRAMMING:
As mentioned earlier, before you can use your
newly installed hard drive, the drive must be
low-level formatted using the PREP utility, then
partitioned using the PART utility, and then
each partition formatted using FORMAT.
The PREP and PART utilities were available on a
disk entitled 'Winchester Utilities Disk',
distributed separately from the earlier MS-DOS
versions. Instructions are available on disk
from the Z-100 LifeLine Library.
The actual procedures to run PREP are beyond the
scope of this article. However, before running
PREP, a Format Enable Jumper must be reposi-
tioned on the Z-217 Winchester Controller Board.
Note: The Format Enable Jumper provides protec-
tion against the complete, unintentional erasure
of your hard drive, so once you have completed
PREP, make sure you reposition the jumper to its
harmless storage position.
Figure 13.
Format Enable Jumper
11

Perform the following:
[ ] Referring to Figure 13, remove the Z-217
Winchester Controller Board from the card cage
far enough to remove the Format Enable Jumper
from its storage position between pins 3-4 at
the lower left corner of the card and install it
just below the power supply connector. You may
have to disconnect some cables to do this.
[ ] Replace the board in the card cage and
reconnect any cables that had to be disconnected
to remove the board. Make sure that all cables
and boards are fully seated in their respective
connectors.
[ ] If the computer is a Low-Profile model, be
sure to connect the monitor to the computer and
turn it on.
[ ] Connect the line cord and apply power to
the Computer.
Caution: High voltages are present at locations
around the CRT in the All-In-One computer (See
Figure 8). Avoid touching the picture tube at
the large, single cable attached to the top
surface of the tube!
[ ] Insert the Winchester (Hard Drive)
Utilities Disk in floppy drive A and Boot the
computer. Proceed with PREP.
Note: I have created a paper listing the PREP
specifications for nearly every hard drive that
could be used in the Z-100. Please see the file,
MFMHardDriveSpecs.PDF, that accompanies this
article.
Once PREP has been completed, you must turn off
the computer, disconnect the line cord, and
reposition the Format Enable Jumper back to its
storage position on the Winchester Controller
Board. Proceed with the following:
[ ] Referring to Figure 13, remove the Z-217
Winchester Controller Board from the card cage
far enough to remove the Format Enable Jumper
from its programming position just below the
power supply connector and install it in its
storage location between pins 3-4 at the lower
left corner of the card. Again, you may have to
disconnect some cables to do this.
[ ] Replace the board in the card cage and
reconnect any cables that had to be disconnected
to remove the board. Make sure that all cables
and boards are fully seated in their respective
connectors.
[ ] Install the cover on the computer.
[ ] Connect the line cord and apply power to
the Computer.
[ ] Reboot and proceed with the PART and
FORMAT utilities.
[ ] Copy the desired operating systems onto
the hard drive.
DRIVING US CRAZY, BUT FOR A REASON
by (C) Alan Brenden, 7/09/92
In the early days of the PC, there wasn't much
involved in deciding when a new hard disk was to
be bought or repaired. The first hard disks used
Seagate's ST506 technology and that was your
choice.
Times and technology have changed and today's
high-performance systems make it necessary to
match the needs of the system to the storage
technology. This article will try to explain
what's behind these drives that drive us crazy -
MFM, RLL, ESDI, IDE, and SCSI.
ST506/412 (MFM & RLL) Interface:
Originally, the ST506 drives used an encoding
method know as Modified Frequency Modulation
(MFM).
As the need for bigger drives evolved, a new
encoding method was developed to pack data
tighter together. Known as Run Length Limited
(RLL), this method involved looking at groups of
16 bits rather than each individual bit. This
achieved a kind of compression of the data that
allowed roughly 50% more on a disk than MFM. The
trade off was that you needed a higher grade of
media and timing was more critical.
As prices for media dropped, RLL drives have
just about wiped MFM drives from the market
place. ESDI, SCSI, and IDE also use a type of
RLL encoding.
ST506/412 drives have 2 cables, a 34 pin control
cable and a 20 pin data cable.
ST506 MFM has a data transfer rate of 625K bytes
per second and a storage capacity of 5 - 100 MB.
ST506 RLL has a data transfer rate of 937K bytes
per second and a storage capacity of 30 - 200
MB.
ESDI:
ESDI (Enhanced Small-Device Interface) was
developed to allow faster transfer rates and
high disk capacities. Greater intelligence
reduced the amount of communication between the
drive and the controller. The transfer of data
between the drive and the controller used a
pulse code that wasn't required to return to
zero between pulses, as did ST506. This was
therefore known as Non Return to Zero (NRZ) and
increased data transfer.
ESDI uses the same cables as the ST506 but the
two can not be mixed. ESDI is CPU controlled and
is suitable for single tasking environments.
ESDI has a data transfer rate of 1-3M bytes per
second and a storage capacity of 80 MB - 2 GB.
One controller can handle up to 2 drives with
multiple controllers possible.
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IDE:
As the name implies, IDE (Integrated Drive
Electronics) combines both the disk and the
controller on the same unit. Only a simple
interface is needed and typically it is built
directly into the motherboard. If the interface
is not built into the motherboard, a simple
paddle-board is used and, because so little
electronics are needed, an additional serial and
parallel port is sometimes included.
The IDE drive transfers only data and doesn't
need to send format and sector information as
does ESDI. Therefore, the data transfer rate can
be 3-4 times faster then ESDI.
The IDE drive is not a device level interface
and has the ability to lie to the BIOS and give
the logical appearance of a known device type,
while physically it may be totally different.
You won't see bad tracks on an IDE drive,
because the drive hides them. Because of this,
you can not low level format an IDE drive
without specific utilities for that drive.
IDE uses a single 40 pin cable. Limited to a 2
foot cable length and 2 addresses, no termina-
tion is needed. The first drive is configured as
the master and the second as the slave.
IDE has a transfer rate of .625 - 2M bytes per
second and a storage capacity of 20 - 500 MB.
SCSI:
SCSI (Small Computer Systems Interface),
pronounced "scuzzy", is a more general version
of the IDE interface. SCSI hard disks boast the
fastest transfer rates of all the discussed
technologies, with SCSI 2 having a transfer rate
up to 40M bytes per second.
SCSI implements 2 ways of boosting transfer
rates, fast and wide. FAST SCSI doubles the
clock speed, and WIDE SCSI increases the bus
width.
SCSI also implements other performance features,
including controller based RAM caching and tag
command queuing. By queuing commands, the SCSI
controller can free up the CPU to do other tasks
while it finishes its task. SCSI also has the
ability to transfer data to another SCSI device
without CPU involvement.
SCSI uses a single 50 pin cable with devices
daisy chained together and terminated on both
ends. Seven devices can be installed per
controller with up to four controllers.
SCSI 1 has a data transfer rate of 1-5M bytes
per second and a storage capacity of 20 MB - 1.5
GB.
SCSI 2 has a data transfer rate of 1-40M bytes
per second and a storage capacity of 40 MB - 3
GB.
WHICH IS BEST?
Performance isn't without price. Many applica-
tions don't need the performance of SCSI, which
is, by far, the most expensive. IDE or ESDI will
usually suffice for most applications. IDE is
presently the cheapest of the three. SCSI, how-
ever, has the added advantage of the greatest
expandability. So, if you need SCSI, the money
is well spent.
Thanks Alan.
Well, good luck with your Z-100 MFM Hard Drive
installation. If you have questions or comments,
I can be reached at [email protected].
Cheers,
S.W. Vagts
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