The Datamaster was IBM's only 8-bit microcomputer and one of the few to use the
EBCDIC encoding. Model 5322 is an integrated unit with a
CRT screen, keyboard, processor, memory and up to two internal 8-inch
floppy drive units. Model 5324, labelled "ergonomic", is
tower-based and contains the same components as the 5322 except for screen and keyboard. Internally, both models use the same motherboard.
Hardware Its microprocessor is an
Intel 8085 clocked at 3.07 MHz, with a bank system that enables allocation of 272 KB ROM and 128 KB
RAM. The computer has four internal
expansion slots. Design and development of this machine was made mostly using off-the-shelf
integrated circuits of that time. This means they used microprocessor and support ICs which were available on the market, particularly the
7400 series of support chips. This marked a radical change for IBM, which previously had always used their own
semiconductor families (like the
SLT family). Even so, in order to deter third parties from producing
clones, all components were relabelled with internal references determined by the company. This component redesignation is the main issue repairing this kind of machines, and as a consequence a large number of units remain with faults. This system's
read-only memory originally used fourteen 8KB memory modules, for a total of 112KB. ROS, IBM's term to refer this kind of memory, Is numerated in order to be identified during the diagnostics. The Datamaster's ROM memory is prone to corruption during its ageing process. Unlike other microcomputers from the era, the System/23 uses 9-
bit RAM instead of the simpler 8-bit one. This is due to the use of the ninth bit to store
parity data. This storage is part of an error-detection mechanism that is used to detect errors in the memory during runtime. In case of finding such an error, the system generates an interrupt and is halted. Finally, it is necessary to explain that the integrated circuits employed in its RAM are unusual in the sense that they are piggybacked, fact that spread rumors that the memory was redundant when in fact they are a variant of the TMS4116, the TMS4132. The video subsystem of this computer is based on the Intel 8275. This component has the responsibility to generate sync signals, among other functions. The section is almost copied from the datasheet of this component. As a curiosity, it has support for light pen, and it has a mechanism to simulate it during diagnostics. The video memory is not dedicated, unlike integrated circuit-based computers such as the
TMS9918 or similar. The symbols are defined in a character generator which consists of eight pages (one per region/language supported) of 128 glyphs each. The 128 character limit is due to the width of the internal queues of the 8275, which uses seven bits to define a character. The Datamaster's BASIC is a closed environment, as it was decided the users wouldn't be able to access directly the hardware resources and as a consequence this dialect lacks low level commands such as
PEEK and POKE. IBM did not provide the owners of the machine to program the computer at the low level, leaving interpreted BASIC as the only option. A distinctive point for this microcomputer is its advanced diagnostics firmware. The checks are done on the CPU, RAM, ROM and all the main integrated circuits that are present in the motherboard. This set of routines are called PID-1200 or POD, according to the diagnostics and service manuals, respectively. These procedures show the results through the screen whenever possible, and through a probe otherwise. This firmware is accurate enough to pinpoint a failing memory and it could also determine if it is present or is missing under certain circumstances. ==Influence on later IBM systems==