GUBBINS@RADC-TOPS20.ARPA (Gern) (12/29/87)
Zenith H/Z-100 Upgrade Series Part 2 20-NOV-87
INFO-HZ100 Gern
The Evil Blue Empire and the Darker Side of the Z-100
The Evil Blue Empire
--------------------
The competitive situation when the Z-100 was introduced in 1982 can be
summarized as follows: The IBM-PC and Apple III did ALMOST as well in
monochrome as the Z-100 did in 8 colors. The Z-100 is always in 'graphics
mode' ('text' being so much graphics) eliminating all the problems of
mixing text and graphics and different screen modes of operation of the
other microcomputer systems. As an added bonus, the Z-100's character font
and keyboard codes are both completely software redefinable. The Z-100
contains two RS-232C serial ports, a Centronics compatible parallel printer
port, light pen input, and composite and RGB video outputs. These
peripherals are built into the machine so that separate S-100 cards are not
needed. The IBM-PC/XT/AT contains no peripheral support, requiring extra
cards to provide all I/O and video at additional cost.
The Apple III did not survive very long. The IBM-PC has been modified and
enhanced many times over from the original 16K, cassette tape based,
4.77MHz, 5 slot machine in an effort to make it fast enough and usable
enough to fill the current computing demands of the present. The
IBM-PC/XT, AT, PS/2 video (or initially the lack thereof) has spawned the
MDA, Hercules, CGA, PGA, EGA, MCGA, and VGA Video - each mode mostly being
incompatible with the others and creating a software nightmare.
Every evaluation comparing the Z-100 and the IBM-PC rates the Z-100 as the
technically superior machine. This resulted in major contracts for the
Z-100 with the military, Clarkson University, and many others. The Z-100
was made the Air Force/Navy Standard Microcomputer System. Under the terms
of the contract, Zenith Data Systems, would supply a minimum of 6000 (over
10,000 were actually ordered) Z-100s over a period of three years. The
total amount of the contract was estimated at $29,276,679.
The Z-100 is disk file compatible to the IBM-PC/XT machines. That is, the
machines can both directly read and write each others disk files under the
MS-DOS based operating systems (MS-DOS for Z-100, PC-DOS for IBM-PC/XT).
Any program that is written to be MS-DOS compatible will run under both the
Z-100 and IBM-PC. Any program which bypasses the operating system software
and uses hardware particularities (Graphics, etc...) or ROM based routines
will only function correctly on the machine it was designed for. The
versatile structure of the Z-100 allows a great deal of freedom in
redefining the hardware and software making PC emulation in software very
possible (ZPC V2 is a good example).
Unfortunately, the field is now dominated by the IBM and clone designs.
IBM's influence on the market was far greater than any company realized at
the time. IBM was spending more money in advertising the IBM-PC than ZDS's
total computer sales. ZDS (as well as Tandy/Radio Shack, Texas
Instruments, and Sanyo - each with non-PC compatible MS-DOS machines)
realized from the start that it was impossible to out-advertise IBM. IBM
spent nearly $50M in advertising the PCjr. alone, the machine that failed
in the marketplace.
Z-100 Little Known Features
---------------------------
The superior design of the Z-100 includes several innovative circuits that
have never really been put to use at the present time. The Z-100 hardware
includes memory management, extended addressing, and light pen support.
The light pen is only now starting to be supported.
The Z-100 RAM system has bank switching memory management ability for use
in muti-user operating systems. This system allows for the dynamic
rearrangement of sections of the RAM addressing scheme. This system was
used by the very obscure Z-100 MP/M Operating System that never caught on.
There is extended addressing circuits which provide up to 16 Megabytes of
addressing capability, in accordance with the IEEE-696 S-100 standard. The
8088 CPU accomplishes this by latching data onto address lines A20 through
A23. The 8085 similarly can use this latch to address a location above its
64K of address space. This system can be used to provide up to a total of
16 banks of 1Megabyte of RAM and or up to 16 virtual Z-100s running on one
machine. To my knowledge this hardware feature has NEVER been used.
The light pen port permits using a light pen with the Z-100. When the
light pen is placed near the CRT and detects a pixel, it strobes the CPU
and the video board. Circuits on the video board store the location of the
detected pixel. The user must supply the software to process this
information (such as moving the pixel or drawing a picture). The program
must set up the proper interrupts, handle timing, and take care of bit
locations pointed to by the light pen. GW-BASIC V2 for the Z-100 now
contains light pen support. HUG and other vendors currently have light pen
support packages for the Z-100.
The Darker Side Of The Z-100
----------------------------
Barry Watzman did the architectural design of the Z-100. In a Sextant
interview, Watzman states that the Z-100 design goal was to provide the
best combination of display, memory, and disk I/O. The 8085 was included
to as a bridge to existing CP/M software. When the Z-100 was introduced
there was very little 8088/8086 software available. The Intel 8087 Math
Co-processor was not included in the original design because the chip was
very expensive at the time, lack of PC board room, and lack of software to
utilize it. Running at faster than 5MHz was planned from design start.
During development, a Z-100 was running at 11MHz. Barry Watzman left ZDS
mostly because ZDS management did not believe in the Z-100, and abandoned
it in favor of higher profits as a PC clone maker. ZDS never did all that
was possible to make the Z-100 run PC software. The Z-100 could easily be
make to include IBM ROM BIOS support in the IO.SYS module making it very PC
compatible (Hint for software developers!).
The Z-100 design is not perfect and has its drawbacks. It (like the
IBM-PC/XT) is not a true 16-bit machine. The Intel 8088 is a hybrid 8-bit
CPU with the functional capabilities of the Intel 8086 (a true 16-bit CPU).
The Z-100, with its IEEE-696/S-100 bus, will accept other CPUs as slave
processors which must be able to utilize the Z-100's fixed 5MHz or 8MHz
system clock. The Z-100 does not have a detachable keyboard, which may be
an undesirable feature to some persons. The machine has a high capacity
cooling fan which makes it rather noisy in quite environments. The Z-100
has a FCC RF emission classification of a type B machine - for use in a
commercial environment. Use of a Z-100 in a residential area may cause
some interference to radio and television reception. The Heathkit version
(H-100) has a metallic coating sprayed on the inside of the case and the
FCC classifies it as a type C machine - for use in a residential
environment. The terminal characteristics are that of an H-19 (enhanced
DEC VT-52) and not ANSI, but the Z-100 can be made to emulate the ANSI (DEC
VT-100) terminal with the proper software or the ZANSI Driver. MS-DOS
caught on unexpectedly quickly and caused the rapid demise of the CP/M
Operating System 8-bit world. The Z-100's 8085 CPU quickly became a wasted
effort which PC board space would have been better used on an 8087 Math
Coprocessor. The 8087 support baby board add-on is a kludge, but it works.
The Z-100 with its single motherboard and piggy-backed video board makes
system functions difficult to replace or upgrade. If the completely carded
designs of the S-100 machines and the ZDS PC compatible machines had been
used in the Z-100 design, it would have greatly increased the flexibility
and lifetime of the machine.
The ZUpGrade Series
-------------------
Z-100 is now over 5 years old but its advanced features still allow it to
be easily enhanced and remain technologically current with some effort on
the part of the user. The Z-100 can already be enhanced and expanded by:
converting it into a portable, making a detached keyboard, up to two 65MB
harddisks, 1 MByte RAM, almost unlimited RAMdrive space, music & sound
effects, advanced speech, analog and digital joysticks (tracballs),
real-time clocks, mice, high resolution non-interlaced multisynched video,
and can run quite a lot of IBM-PC software with only a software driver.
The Z-100 can continue to be enhanced beyond its original design by:
10.7MHz operation, 64 or more colors per pixel, video output lookup tables,
10MBit/sec Ethernet LAN with TCP/IP, and more. In the software realm,
MIMIX (a PC version of UNIX) should be very easy to port to the Z-100 with
a little effort by good programmers. I am slowing working on these future
upgrades.
I do not have all the answers, just most of them. The Z-100 is a
wonderfully complex machine and I do not, as yet, understand all of its
operation. This Z-100 Upgrade Series that I am attempting to crank out is
my effort to help other Z-100 users get the most out of the Z-100. The
INFO-HZ100 email group of which this is a part is a FORUM for discussion, I
can't come up with all the wonders on my own (especially software). The
only programming language I am really good at is Solder. If WE are going
to get the most out of our Z-100s, then everyone must help me out, ask
questions (I make mistakes on rare occasions), add to the discussions, and
experiment! Let US continue to keep the Z-100 alive and powerful!
Cheers,
Gern
P.S. - Next: The beginning of the stuff you really want to know.
All about the Z-100 Switching Power Supply
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