Cromemco System One CS-1

CS-1

The Cromemco CS-1, or System One, computer was introduced in 1981 and the base model retailed for around $3995. Cromemco had previously released the Z-1, Z-2, and System Zero computers. The basic CS-1 is powered by a 4-Mhz Zilog Z80 CPU. It comes with an 8 slot cage so users can expand the system. There are dual quad-density 5 1/4″ floppy disks for a total of 780K of storage.

CS-1H

A key is required to unlock and power on the unit. The early Cromemco CS-1H has a single 5 1/4″ floppy drive as well as an internal 5″ Winchester 5 Megabyte hard drive.

By 1984 Cromemco had eight versions of the System One.

  • CS-1 : Z-80 with ZPU, 64K RAM, 2 390K 5 1/4″ floppy disks, $3995.
  • CS-1H : Z-80 with ZPU, 64K RAM, 21 MB hard disk, WDI-II Controller, 1 390K 5 1/4″ floppy disk, $6995.
  • CS-1D5 : 68000/Z-80 with DPU, 512K RAM, 2 390K 5 1/4″ floppy disks, $5495.
  • CS-1D5E : 68000/Z-80 with DPU, 512K ECC RAM, 2 390K 5 1/4″ floppy disks, $6495.
  • CS-1H21D5 : 68000/Z-80 with DPU, 512K RAM, 21 MB hard disk, STDC controller, 1 390K 5 1/4″ floppy disk, $8495.
  • CS-1H21D5E : 68000/Z-80 with DPU, 512K ECC RAM, 21 MB hard disk, STDC controller, 1 390K 5 1/4″ floppy disk, $9495.
  • CS-1H50D5 : 68000/Z-80 with DPU, 512K RAM, 52 MB hard disk, STDC controller, 1 390K 5 1/4″ floppy disk, $9495.
  • CS-1H50D5E : 68000/Z-80 with DPU, 512K ECC RAM, 52 MB hard disk, STDC controller, 1 390K 5 1/4″ floppy disk, $10495.

The S-100 bus cards are mounted horizontally in a steel box inside the back of the unit.

Here is Cromemco’s 64KZ board.

Here are the two floppy disks mounted inside the chassis.

The CS-1 has 64K of RAM which allows it to easily run Cromemco’s proprietary RDOS operating system. User’s could buy the Writemaster software to add word processing capabilities as well as database software and software to interface with a light tablet and pen.

Above is the DPU (Dual Processor Unit) board used in the CS-1D5 and up. It has both a Z80 and 68000 CPU chip! The chips are under software control so the programmer can choose which chip to use for any particular application.

Above is the Memory Storage Unit (MSU) board. This is the 512K version.

The CS-1 can support a number of languages including Structured BASIC, FROTRAN, COBOL, C, RatFor and LISP. It is also capable of running Cromix (like Unix) for a multi-user environment.

Notably, the Cromemco CS-1 made a brief appearance in the 1984 movie Ghostbusters.

A parallel port on the back allows the CS-1 to interface with a printer. There is also a serial port for a CRT monitor.

Here you can see the CS-1 with Cromemco’s high-capability terminal and printer.

The Cromemco System One doesn’t come on the market very often. The most recent sale was for a completely untested unit without the key which sold for $1600 in February of 2020.

Available on eBay

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