# Cromemco Z-1 replica

# Overview

Cromemco was a notably more successful microcomputer manufacturer than IMSAI, despite the iconic status of the IMSAI 8080.

Initially producing add-on cards and peripherals for other S-100 computers, notably the Cyclops Camera, Dazzler graphics interface and D+7A digital & analog I/O interface, Cromemco went on to produce a family of related microcomputers initially powered by the Zilog Z80 microprocessor and then later incorporating both the Z80 and the Motorola 680x0 series of microprocessors.

Their first complete microcomputer was the Cromemco Z-1

From its appearance you might think it is just a rebadged IMSAI 8080, but that is not the case (no pun intended).

Cromemco OEM'ed the front panel, chassis & lid for the Z-1 from IMSAI but the internals were all produced by Cromemco, and at its heart was the Cromemco ZPU CPU board powered by the Zilog Z80 microprocessor.

Although this computer could run CP/M, Cromemco produced their own CP/M (v1.33) like operating system, Cromemco DOS, CDOS.

Cromemco then followed their own path producing the Cromix operating system. A multitasking, multi-user, UNIX-like operating system running on the Z80 with banked memory. The last release of Cromix (version 11.27) for the Z80 was in 1984. Cromix continued to be developed but only for the 680x0 series of microprocessor based Cromemco computers.

What you see in the photo above is the Cromemco Z-1 replica kit produced by TheHighNibble. Identical to the IMSAI 8080 replica kit except for the text and logos on the front facia (see: the Bill-of-Materials.

Also powered by Udo Munk's z80pack, specifically the cromemcosim machine, running on the ESP32 micro-controller targeting the ESP32-PICO-KIT.

# Features

The Cromemco Z-1 replica can run:

• CP/M
• Cromemco DOS (CDOS)
• Cromemco Cromix (up to version 11.27)

on a simulated Z80 microprocessor at 2 or 4 MHz (or "unlimited" at approximately 5MHz), with up to 8 banks of 64KB of RAM.

There is support for up to three (3) UARTs (physical or virtual), so Cromix is configured with three (3) TTY devices and can support up to three (3) simultaneous users since it is a multitasking, multi-user, UNIX-like operating system.

The Cromemco Z-1 machine emulation (Z80PACK, cromemcosim) includes the following emulated hardware configuration, following standard Cromemco memory and I/O port mapping:

• ZPU - Z80 CPU @ 2MHz, 4MHz or Unlimited (~5MHz)
• 64KB of RAM in Bank 0
• seven (7) additional banks of 64KB of RAM as Banks 1 to 6
• 16FDC/64FDC hybrid floppy disk controller
  • with 4 floppy disk drives (typically A: to D:)
  • that can behave as 5 1/4" or 8" drives SS/DS, SD/DD
  • based on the *.dsk floppy disk image that is mounted
  • banked ROM support for RDOS ROMs
  • the console serial interface (TU-ART) as the TTY: device
  • Real Time Clock (RTC) (512ms timer)
• WDI-II winchester (hard) disk interface
  • with up to 3 hard disk drives (typically hd0:, hd1: & hd2:)
  • each emulating a 10MB capacity 8" IMI-7710
  • the WDI-II will work with the CPU set to any speed as it reflects all timing relative to a 4MHz CPU
• additional TU-ART communications interface with
  • two (2) additional serial interfaces as the TTY2: and TTY3: devices
  • two (2) parallel printers as lpt1 (LPT:) and lpt2 devices
• Dazzler graphics
• D+7A I/O with joystick input support

Like the IMSAI 8080 replica, the Cromemco Z-1 replica also comes with a web based desktop user interface that provides access to a range of virtual devices including:

• 3 simulated TTY terminals (VT100 &/or Cromemco 3102 Video Terminal compatible)
• 1 line printer, 80/132 column selectable
• 4 simulated 8" floppy disks
• Cromemco Dazzler graphics interface
• Cromemco D+7A I/O including JS-1 joystick emulation (from connected USB joystick)
• Paper tape punch/reader
• Manuals library
• Disks library
• Paper tapes library

# Availability

The Cromemco Z-1 replica has been available to order and in production since October 2022.

# Expression of interest

I am accepting expressions of interest via email. If you send email to info@thehighnibble.com I will add you to the list.

Please specify that you are interested in the Cromemco Z-1 replica.

Once a kit is available for you within the month, I will contact you to confirm your order.

The price for the kit is USD$300 and in addition you also pay for postage and any PayPal transaction fees.

# News & Updates

You can stay up-to-date with news about additions to this site, or new YouTube videos demonstrating the features of the kits by following on Twitter @TheHighNibble and subscribing to TheHighNibble YouTube Channel

# Forum

TheHighNibble forum has been set up on GitHub. The forum is public and readable by anyone but if you wish to post you need to become a member.

Membership requires you to have GitHub account. Email to info@thehighnibble.com with your GitHub name and I will send you an invite to join the discussion forum.

# Specifications

# Dimensions (built)

17 1/8" x 7" x 2 11/16"

435mm x 178mm x 68mm

(width x height x depth)

# Weight (built)

4.22 lbs

1.915 kg

# Power

5VDC @ 500 mA (max., < 100mA typical) - USB micro-B plug required

# Dimensions (boxed/shipped)

18 1/3" x 7 1/2" x 3"

465mm x 190mm x 75mm

(width x height x depth)

# Weight (boxed/shipped)

less than 5.1 lbs

less than 2.3 kg

# Bill-of-Materials

The Bill-of-Materials for the Cromemco Z-1 replica is the same as for the IMSAI8080 replica Bill-of-Materials with the exception of the front panel facia.

Here is a side-by-side image of the two facias so that you can see the differences.

# Recommended tools for assembly

# Step-by-step assembly guide

# Configuration

# Updating Software

The ESP32 can be reflashed (using Over The Air updates) with the Cromemco Z-1 firmware.

# Troubleshooting (draft)

# Enhancements and Add-ons

# Planned

• emulated Cromemco SDI - Super Dazzler Interface (hi-res graphics adapter)