James Wigeri van Edema

Sergei Vasilyev

UyenThao Huynh

Amante Agbannaoag

Mary E. Dutton

Date: May 14, 1999

Assignment: Class Project

Instructor: Asst. Professor Sadighian

When we started our research by looking over the obsolete computer hardware we really concentrated our efforts on the two huge towers (Figure 1). It was very easy to overlook the seventy-five pound beige terminal with the green phosphor screen, 8" dual floppy drives (), and integrated keyboard (Figure 2). As a matter of fact, the first time we looked over the unit, we referred to it as the input/output terminal for the 5247 Magnetic Disk Unit. That’s until we found a German magazine article that identified the unit as the System/23 Datamaster (Mehr Hardware fur IBM System/23, Computerwoche, 1982). The Microcomputer shown in Figure 3 one happens to be one of IBM’s first, but unsuccessful attempts at manufacturing a Personal Computer.

The Datamaster or System/23, designed in the late seventies, was one of IBM’s prototypes for the modern PC. The architecture of the Datamaster had much in common with today’s PC. The Datamaster used the Intel 8085 processor, which was an 8-bit processor with an 8-bit external data bus, and a 64K-address limit. The motherboard had an 8-bit expansion bus that ran at 4.77 MHz and used 62 pin connectors. The system board also included a DMA controller. IBM waited until 1987 to publish full specifications on the expansion bus, which is now more commonly referred to as the 8-bit ISA (Industry Standard Architecture) bus (Figure 4). The computer is bulky and weighs about seventy-five pounds. The single unit houses the motherboard, Keyboard, CRT, and two 8" floppy drives. The floppy drives were borrowed from the IBM 3740 Data Entry System. So why did the project fail?

The PC project failed for several reasons. IBM wanted to design a closed system that ran on an IBM Operating system, used IBM applications, and was compatible with the IBM standards and programming languages. The Project fell behind schedule because while the hardware was ready to go, the software was still 1.5 years away due to all of the extra requirements mentioned above. A couple of additional reasons were that IBM had a limited amount of applications available, and the unit was greatly overpriced. Moreover, by the time the unit was ready for release, the market already offered similar products with 16 bit processors. Although the unit failed to make it to the market as the first IBM PC, it did enjoy some success as a small business computer, offering accounting and word processing applications. System/23 performed this role through the use of a couple of external units, and this is where the two towers come in.

The towers are the 5247 Magnetic Disk Unit, and the 5324 System Unit. Both towers have a system board with an 8-bit architecture. The 5247 disk unit has a 15 MB 8 " hard drive capable of data transfer rates of 1.2 MB/sec (Figure 5).

The unit has 4 expansion slots, and can support up to four 5324 System units concurrently (Figure 6).

The components, cables, and hardware are huge when compared to today’s computers. Most of the I/O ports and connectors resemble their counterparts on today’s computers, but it’s obvious that the same standards were not used then. The 5324 System unit has an external monitor and keyboard. The monitor is powered from the 5324 through a cable with a canon plug connector, and uses a 15-pin D-type connector for the monitor interface cable. The keyboard connects to the 5324 through what resembles a DB-25 connector, instead of a DIN connector. The hard disk in the 5247 Disk Unit communicates with the controller expansion card through a ribbon cable, but it’s a hard plastic cable instead of the flexible cables you expect to see in today’s systems (Figure 7).

We also found an external switch box that we expect went to an output device like a printer. The printer that usually accompanied the small business system was a daisy wheel printer 5217 capable of printing about 60 characters/sec.

In conclusion, although the Datamaster didn’t make it to the market as the first PC, it did have a big influence in the design of the 5150 IBM PC. Many members on the 5150 design team came form the System/23 Project. The 5150 IBM PC was designed around the 8088 processor, which was a 16-bit processor with an 8-bit external bus. This was done to keep the cost of the computer down and to use some existing hardware. The design team borrowed the keyboard, DMA controller, interrupt controller, and expansion bus from the Datamaster. This also allowed them to adapt some of the Datamaster’s expansion cards to the new PC. IBM also needed an operating system for the new PC. They wanted to use what was then the premier operating system for microcomputers called CP/M, but when snubbed by Gary Kildall’s Digital research Intergalactic, IBM approached a small company that specialized in a Basic programming language and Compiler. The name of that company was Microsoft, but that’s a whole other story.