Unisys A-series

The Unisys A-series followed on from the Burroughs large systems family,  B6500-B7900. The introduction of the new family of machines corresponded to changes to the e-Mode instruction set architecture which Unisys undertook to clean up the design and extend the memory address range.

The A-series was eventually replaced with the LX, NX series in the 1990s and finally Libra series of mainframes in the 2000s. The larger models contain CMOS CPUs implementing the evolved e-Mode architecture. The smaller systems are based on Intel x86 CPUs and host e-Mode via an emulator product known as MCPvm (wrapped up in the ClearPath product family). Some configurations include a mix of native e-Mode CPUs and x86 so that Windows NT / Unix and ClearPath MCP can co-exist in the same hardware system sharing disk, network and other peripherals (particularly tape drives and terminal concentrators).

Unisys SCAMP (Single Chip A-series Mainframe Processor)

This single package under a large silver cover is a multi-chip-module (MCM) - it contains the core processing logic chip surrounded by 10 static ram chips which contain the microcode personality loaded at bootstrap time by the host. In the smaller systems like the A1 / A4 / A6 these machines contain a 80186(TBD?) which controls the initial microcode load. In the PC desktop based machines like the microA and A7, where the SCAMP processor is located on an ISA or EISA plugin card, the host CPU (either a Intel 80386 or 80486) running OS/2 hosts the system loader and manages the initial microcode load.

Unisys A1 / A4 / A6 / System 80/7E

The small cabinet (low-end) range of A-series machines with designations such as A1, A4 and A6 used the same processor cabinet with variations on the amount of memory, disk expansion and presumably processor clock speed (based on the differences which existed in the reported benchmarks). The Unisys System 80/7E used the A4 configuration but loaded different microcode into the SCAMP to support the Univac System 90 architecture, which in turn was based on the IBM 360/370 architecture, using the Univac developed OS3 operating system.

A typical Unisys A6 configuration would consist of: dual SCAMP CPUs (picture below shows two SCAMP CPUs on an A4 / System 80/7E CPU board) , 48MW (48-bit words + ECC + tag bits, approximately 384Mbytes of memory), 15 terminals, 1200 LPM (lines per minute) line printer, 3.2GBytes of hard disk, CP2000 communications processor supporting X.25, TCP/IP, BNA (Burroughs Networking Architecture) running MCP version 3.9.2 providing programming languages such as LINC, DMS II, COBOL, C, Pascal, ALGOL, FORTRAN and PL/I.  This example configuration is a translation of recursos-computacionales/a6.html
.A4 / System 80/7E dual CPU board


DS (USA) snapped these pictures of a Unisys A6 which was being de-commissioned in 2003 . This system consists of the CPU and an expansion cabinet. The console terminal is sitting on the expansion cabinet, terminal type is unknown but appears to have the K series keyboard layout (note the two columns of function keys at the left side of the keyboard). The right hand picture shows the desktop 9-track SCSI tape drive system and the small tower to the right contains the DDS tape drives (top, middle), the device below the two DDS tape drives has not been identified.


LR(USA) captured a video of a Unisys A6 MCP system start in 2010. The A6 in this video appears to be identical to DS(USA) with two cabinets, sitting on top of the right-hand expansion cabinet is the desktop SCSI 9-track tape system, and to it's left are the DDS tape drives in a small tower unit. The terminal is a Unisys T-27.


Unisys A7

The Unisys A7 had two system cabinet variants, the MP 4668 ISA / EISA PC tower (left-hand system in picture below) and the larger cabinet for the system known as the A7-411.

The smaller A7 was a fairly standard PC tower style  system with a mainboard which provide the ISA/EISA backplane, and interconnects for SCSI. The main CPU and memory was added via a plugin card which allowed either a 486 or Pentium CPU. The SCAMP processor board plugs into either an ISA or EISA slot. It is understood that the ISA SCAMP was known as SCAMP-A variant and runs at 4MHz, and the EISA SCAMP-B runs at 8MHz. The SCAMP-B supports a second EISA memory card which allows memory expansion to 96MW fully populated. A ribbon cable connects the two EISA cards together.


Unisys A7 MCP OS/2 based startup 


A second A7 variant (right-hand system in picture below) known as the Unisys A7-411 uses a small waist high cabinet provided more inbuilt disk and tape expansion.



The video below is  from Brasil, and shows the Unisys manufacturing plant making A-series machines including shots of the A1/A4/A6 (System 80/7E) cabinet being constructed.

Unisys E&M Veleiros 1988... from marcusfranco on Vimeo.

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