Carton Label (26 Mar 1991).

Cromemco model: CS 250 ~ MANUALS for the factory installed, S-100 boards.

DIAG (Diagnostic PROMS)

Not available.

64FDX (Floppy controller)

Not available.

GPIB (General Purpose Instrument Bus)

Cromemco GPIB Instruction Manual.pdf

OCTART (Serial I/O)

Cromemco OCTART Communications Processor 023-2028 198402.pdf

ESDC (SCSI interface and controller)

Not available.

STDX (ST-506 MFM hard disk controller)

Not available.

XXU (Motorola 68020 CPU)

Not available.

XMU (Paged Memory Manager)

Not available.

MCUX (Memory Control Unit)

Not available.

MSU (1M RAM memory)

Not available.

oards & hardware that came with this Cromemco CS-250 system (circa, March 1991)

DIAG (On-board Diagnostics, in EPROM's.)

64FDX (Double-density floppy disk controller for 5.25" & 8" diskettes)

GPIB (IEEE-488, General Purpose Instrument Bus.)

OCT (The OCTART board is an optional unit for expanding the number of users or adding serial devices to either the System 250 (or System 100,
System /300. 
The OCTART has its own processor and memory for minimum system overhead. Each OCTART has 8 serial channels, and up to 16
users can be accommodated by adding two OCTART boards to a system.)

ESDC (SCSI controller)

STDX (The STDX is a high performance, intelligent ST506 Winchester disk controller (MFM formatted) that includes a dedicated microprocessor and a
4-track cache
memory for high speed operation. It automatically verifies information written to the disk with a read-after-write cycle to assure data integrity.) 

XXU (The XXU is a high performance 32-bit processor board - Motorola 68020 - 20mHz.)

(The XMU board provides demand-paging memory management, and many advanced features, such as scatter loading, that increase processing
and optimizes memory utilization. Context switching is done in a single instruction time for fast response when switching from user to user, or
task to task. The result is that multiple users can be added to the system with minimum degradation of system performance.)

MCUX (Memory control unit)

2MSU (2 each) (The 2MSU board is a 2 megabyte RAM board that is incorporated into the System 250. In addition, 2MSU boards may be added to
incrementally increase the RAM in the system to as much as 16 megabytes.


(click on photo to view Hi-Res photos)

Maxtor XT2190 (The CS-250 includes one, 190-Megabyte, ST-506, MFM, 5.25" full-height, hard disk drive.)

Cromemco CS-250 (With "MegaSafe" removable hard disk drive.)

Slot Card Installation Locations (CS-250's IEEE-696, S-100 boards):


























Board Capacity

20 boards

Open Board Slots




Operating System Installed

UNIX System V and Cromix


100/115/130/220/240/260 volts 50/60-cycle

Power Consumption**

550 watts

Power Supply

+8 volts @ 30A, + 18 volts @15A, -18 volts @15A


12 1/4"H x 19"W x 20 3/4"D  31.1 x 48.2 x 52.7cm


92lbs.  41.8Kg


For 19" rack-mounting

Operating Environment

10-40 C


"Historical Notes on the CS-250 Super-Microcomputer"

In its day, the System CS250 computer offered new and exciting capabilities in a microcomputer.  Those capabilities were achieved within the context of industry standards, such as the UNIX System V operating system, Ethernet, IEEE-696 bus, and a generic 32-bit processor, so that the user had both flexibility and performance. Consequently, these systems could accomplish tasks that once required much larger systems and can gave that performance much more efficiently than in the past.

Cromemco offered many S-100 boards that could simply be plugged into the CS-250 to extend the capabilities of the system, and to meet growing needs. Those extended capabilities options were available to meet most applications and requirements: Graphics, Communications, Memory expansion, Multi-user environments, Computation, Networking, Instrumentation, and to vontrol magnetic storage.

Cromemco's reputation for equipment reliability was earned through the performance of over 50,000 systems (circa 1990) installed around the world. Cromemco was one of the few companies to offer error-correcting memory in microcomputer systems as a further commitment to equipment reliability. They also built-in features such as read-after-write (for checking the integrity of data during write-to-disk operations) The reliability of Cromemco systems was assured on an on-going basis (by a factory quality program which fully met military quality standard 9858A).

The System 250 included the UNIX System V operating system and the CROMIX operating system (Cromemco's proprietary operating system) Those operating systems were pre-installed on the hard disk, so that the end-user didn't have any complicated installation or setup procedures to perform prior to use.

UNIX System V became the standard for this generation of high-performance microcomputers and was installed on all CS-250 systems.  Included with UNIX V were the highly-acclaimed Berkeley enhancements, including CSHELL, TERMCAP, UUCP, and VI. Versatile and powerful, UNIX V provided the multi-user, multi-tasking features required by the day's most advanced applications and opened the door to a very large library of software for your system.

Cromemco's proprietary operating system, CROMIX, was also included on all CS-250 systems (for those users with dedicated application programs and to enable system users to transport their existing software to the newer systems).

Cromemco offered a full range of program development tools and supported programs written in all the popularized computer languages, including C, Fortran 77, Basic, Pascal, and Cobol. In addition, they offered  several leading applications programs, such as the Informix and Unify data base management systems.

In brief, the System CS250 computers were fully supported by programming and applications software. The broad line of software for the UNIX operating systems was expanding every day, so owners could  depend on an even larger base of software in the future.

UNIX -- trademark of Bell Laboratories.
Unify -- trademark of Unify Corporation.
Informix -- trademark of RDS, Inc.
OCTART -- trademark of Cromemco, Inc.
CROMIX -- registered trademark of Cromemco, Inc.

 As of January 2008, I own two vintage CS-250's (both are new USAF MIL surplus). One has not been unboxed since shipment from Cromemco, in April of 1991!

Copyright 2008-2012 ~ TechniQ U.S. Associates LLC & Robert C. Kuhmann
All Rights Reserved (All WRONGS avenged).