The H/Z-100 Series Computer

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The first computers were kits from Heathkit Co.
The Low-Profile, H-110 series computer required
a separate RGB or composite monitor. Zenith
offered the fully assembled version as the
Z-110. When first shipped, it featured:
- 64 to 192k RAM
- Green (std), red and blue video
  planes of 32k or 64k video RAM
  for monochrome or 8 color video
  for a separate monitor
- 5 MHz 8085 8-bit CPU for CP/M
- 5 MHz 8088 16-bit CPU for DOS
- Dual full-height floppy drives, or
  one floppy & one full-height 5Mb
  "Winchester" hard drive
- Two serial ports (DTE & DCE)
- One parallel port
- Light pen port

The first computers were kits from Heathkit Co.
Again, the Zenith version of the H-120 All-In-
One was the Z-120 series. When first shipped,
these computers featured:
- Internal yellow or green display w/25x80
  text or graphics characters
- 64 to 192k RAM
- Green (std), red, and blue video planes
  of 32k or 64k video RAM for
  internal monochrome display or
  8 color video for a separate monitor
- 5 MHz 8085 8-bit CPU for CP/M
- 5 MHz 8088 16-bit CPU for DOS
- Dual full-height floppy drives, or
  one floppy & one full-height 5 Mb
  "Winchester" hard drive
- Two serial ports (DTE & DCE)
- One parallel port
- Light pen port

The back of both computers is very similar,
except that J14 in the Z-110 is a composite
video phono jack. In the Z-120, it is a
brightness control. Other features are:
- Power switch in lower right corner
- A 110v - 220v line switch
- Standard power cord
- A 3" box fan
- J1 - RS-232 DCE serial connector
- J2 - RS-232 DTE serial connector
- J3 - Female DB-25 parallel connector
- J4 - Light Pen connector
- J9 - RGB 9-pin video out connector
- J14 - Composite video or brightness
- Other connector positions are unused
  and covered.

While the only physical external change was to
the front panel to accommodate half-height
drives, by the end of production, Zenith had made
several enhancements to the standard Z-100:
- Half-height, double-density 5-1/2"
  floppy drives
- New 8 MHz motherboard
- 768k RAM maximum
- ROM versions 2.5, 2.8, & 2.9
- Optional Z-204 multi-port board
- Optional Z-205 256k RAM board
- Optional full-height 10 Mb hard drive
- Optional 8087 co-processor board
- Optional ZClock

Other vendors, suppliers, users, and clubs
developed their own enhancements for the
Z-100:
- 768k RAM kit for old motherboard
- Selectable 5-7.5 MHz speedup
- Commercial speedup kits to 10 MHz
- At least one unit operated @ 14 MHz!
- 8087 co-processor board
- MFM hard drives > 32 Mb
- SCSI hard drives >64 Mb
- Smartwatch internal clock
- 1 meg memory board
- Z-205 memory board RAM drive
- LifeLine SCSI/EEPROM board giving
  SCSI hard drive capability
  and fast EEPROM bootup!
- MTR-ROM v3.x and v4.x for support of
  modified Z-DOS v4.x
- LifeLine IDE/NVsRAM board giving
  fast NVsRAM bootup
  Real Time Clock, and
  IDE device capability, including:
    IDE Hard Drives
    Compact Flash Memory
    DiskOnModule(DOM) Memory
- Separate keyboard for computer

Of critical importance was the need to run the up
and coming IBM-PC software. People wanted PC
compatibility. Several vendors engineered solutions
with reasonable success:
- Patrick Swayne of the National HUG (Heath
  Users' Group) developed a software solution
  called ZPC with limited success. The biggest
  problem being the differences in handling
  screen graphics and interrupts.
- He then developed a ZHS board as a hardware
  solution to improve the success of ZPC.
- The ZHS concept was expanded and enhanced
  by Scottie Systems into the Scottie Board, but
  still required the use of ZPC.
- Shortly after, GEMINI & EASYPC became available:
  -- The GEMINI Board, from D.E.L. Professional
      Systems was a daughter board that attached
      directly to the motherboard via the 8088 CPU.
      It had a socket to add an 8087 co-processor
      chip. It also had an additional, optional sound
      board.
  -- The EASYPC from UCI Corporation was
      comprised of a daughter board, new floppy
      controller board, and another S-100 video
      board. It had sound included.
- Both the GEMINI Board and EASYPC System
  provided excellent PC emulation - about 90%
  success. The only main downside was that
  each required the installation of a separate
  Zenith version of PC-DOS in a separate
  partition of the hard drive.

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