View source for IBM System/23 Datamaster

{{Short description|1981 IBM microcomputer}}
{{Infobox information appliance
| name          = System/23 Datamaster
| title         = 
| aka           = 
| logo          = 
| image         = IBM 5322 - computer.JPG
| caption       = 
| developer     = 
| manufacturer  = [[IBM]]
| family        = 
| type          = [[All-in-one PC|All-in-one]] (5322), [[Computer tower]] (5324)
| generation    = 
| releasedate   = {{Start date|1981|07}}
| lifespan      = 
| price         = {{USD|9000|1981}}
| discontinued  = {{End date|1985}}
| unitssold     = 
| unitsshipped  = 
| media         = 
| os            = [[System/34 BASIC]]
| power         = 
| cpu           = [[Intel 8085]] @ 3.07 MHz
| memory        = 32&nbsp;KB,64&nbsp;KB,96&nbsp;KB,128&nbsp;KB DRAM<br />112/128&nbsp;KB ROM<ref name="bitspassats">{{Cite web |date=2025-09-19 |title=IBM System/23 Datamaster |url=https://bitspassats.com/index.php/IBM_System/23_Datamaster |access-date=2025-11-08 |website=Bits Passats |language=en-US}}</ref>
| storage       = 
| memory card   = 0-2 internal 8-inch [[floppy disk]] drives, optional external floppy drives
| display       = Green phosphor [[Cathode-ray tube|CRT]] display (80&nbsp;× 24 text)
| graphics      = [[Intel 8275]]
| sound         = Internal beeper
| input         = [[Model F keyboard]]
| controllers   = 
| connectivity  = Printer port, disk drive port (optional), twinax (optional)
| service       = 
| dimensions    = 
| weight        = {{convert|95|lb|kg|abbr=on}}
| compatibility = 
| predecessor   = [[IBM 5120]]
| successor     = [[IBM Personal Computer]]
| related       = [[IBM Displaywriter System]]
| website       = 
| image_size    = 270px
}}

The '''System/23 Datamaster''' (desktop model 5322 and tower model 5324) was an [[8-bit computing|8-bit]] [[microcomputer]] developed by [[IBM]]. Like the [[IBM Displaywriter System|6850 Displaywriter]], it was one of the first IBM microcomputers, preceding the [[IBM Personal Computer]] (PC), with which it is incompatible. Launched in July 1981,<ref>{{Cite book |last1=Cope |first1=Bill |last2=Gollings |first2=Gus |url=https://books.google.com/books?id=_WC4hKDLqBkC&dq=datamaster+1981+july&pg=PA69 |title=Multilingual Book Production |date=2001 |publisher=Common Ground |isbn=978-1-86335-073-0 |page=69 |language=en}}</ref> the System/23 was IBM's most affordable computer until the PC was announced the following month, proving to be much more economical and popular.<ref name="pollack19810813">{{Cite news |last=Pollack |first=Andrew |date=1981-08-13 |title=Big I.B.M.'s Little Computer |url=https://www.nytimes.com/1981/08/13/business/big-ibm-s-little-computer.html |access-date=2020-03-16 |work=The New York Times |page=D1 |language=en-US |issn=0362-4331}}</ref><ref name="pollack19830327">{{Cite news |last=Pollack |first=Andrew |date=1983-03-27 |title=Big I.B.M. Has Done It Again |url=https://www.nytimes.com/1983/03/27/business/big-ibm-has-done-it-again.html |access-date=2020-03-16 |work=The New York Times |page=Section 3, Page 1 |language=en-US |issn=0362-4331}}</ref>

== Description ==
[[File:IBM_Datamaster_model_5324.jpg|alt=IBM 5324|left|thumb|The 5324 is a tower model which has the monitor and the keyboard separate from the process unit]]
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 [[Cathode-ray tube|CRT screen]], keyboard, processor, memory and up to two internal 8-inch [[Floppy disk|floppy drive units]].<ref name=":0">{{Cite book |url=http://bitsavers.org/pdf/ibm/system23/user_manuals/binder_04/SA34-0107-3_System_23_Setup_Instructions_with_5322_Computer_Jun1982.pdf |title=System/23 Setup Instructions (with 5322 Computer)|publisher=IBM |date=June 1982 |access-date=2025-11-08}}</ref> Model 5324, labelled "ergonomic", is [[Computer tower|tower-based]] and integrates the same components as the 5322 except for screen and keyboard. Internally, both models use the same motherboard.<ref>{{Cite book |date=July 1988 |url=https://bitsavers.org/pdf/ibm/generalInfo/ZA38-0016-0_Commonly_Used_Systems_Parts_Handbook_198807.pdf |title=Commonly Used Systems Parts Handbook |publisher=IBM |page=119}}</ref>

=== Hardware ===
Its microprocessor is an [[Intel 8085]] clocked at 3.07&nbsp;MHz, with a bank system that enables allocation of 272 KB ROM and 128 KB [[Random-access memory|RAM]]. The computer has four internal [[Edge connector|expansion slots]].<ref name="auto">{{Cite web |url=http://www.oldcomputers.net/ibm5322.html |title=IBM 5322 System/23 Datamaster |website=www.oldcomputers.net |access-date=2025-11-08}}</ref>
[[File:IBM_5322_-_PCB_keyboard_controller_from_8122.JPG|left|thumb|Intel 8048 microcontroller relabeled with IBM reference.]]
Design and development of this machine was made mostly using off-the-shelf [[integrated circuit]]s of that time. This means they used microprocessor and support ICs which were available on the market, as well as a dependence to the family of logical components of the [[7400-series integrated circuits|7400 series]]. This marked a radical change for IBM, which previously had always used their own [[semiconductor]] families (like the [[Solid Logic Technology|SLT]] family). Even so, in order to deter third parties from producing [[Clone (computing)|clone]]s, 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.<ref name="5322_service"/> Not long after entering production, the computer was patched and two more memories of the same capacity were added to the motherboard, giving the system a total capacity of 128 KB.<ref name="5324_service">{{Cite book |date=May 1982 |title=IBM System/23 Service Manual |volume=1 |series=IBM 5324 Service Manual |url=https://bitsavers.org/pdf/ibm/system23/fe/SY34-0241-1_IBM_5324_Computer_Service_Manual_May82.pdf |language=en |publisher=IBM |access-date=2025-11-08}}</ref> 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 [[RAM parity|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.<ref name="5324_service"/> Another distinctive trait is that the motherboard contains no RAM, because it is contained in one of two boards that contain the required integrated circuits. Whilst the maximum RAM capacity the computer can manage is 272 KB, the detection and identification system limits the computer to 128 KB.<ref name="bitspassats" /> The available capacities for the memory boards are 32 KB and 64 KB respectively. This implies that the memory capacity for this computer is between 32 KB and 128 KB in increments of 32 KB, being the most common configuration 64 KB. In fact, there are various submodels according of the memory capacity and floppy drive units and type.<ref name="5322_service">{{Cite book |url=https://bitsavers.org/pdf/ibm/system23/fe/SY34-0171-0_IBM_5322_Computer_Service_Manual_Dec80.pdf |title=IBM System/23 Service Manual |volume=1 |series=IBM 5322 Computer Service Manual |publisher=IBM |date=December 1980 |access-date=2025-11-08}}</ref> 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.<ref name="bitspassats" /><ref>{{Cite book |title=TMS4132 Data Sheet |date=November 1978 |url=https://minuszerodegrees.net/memory/4132/datasheet_TMS4132.pdf |publisher=Texas Instruments |access-date=2025-11-08 |language=en}}</ref>

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.<ref name=":2">{{Cite book |title=8275H Data Sheet |date=November 1986 |url=https://www.jameco.com/Jameco/Products/ProdDS/52821.pdf?srsltid=AfmBOoqjn861Ux7WOaruUuFyYNevxOTnWtmFlgR_DCBX8_Ue3pcXntcc |language=en |access-date=2025-11-08}}</ref> 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.<ref name=":2" />  Those pages are selected according to the jumper configuration on the motherboard, but this is done by the software and it can therefore be changed in runtime. The screen field is 80 columns wide by 24 rows high.

The presence of a [[Direct memory access|DMA]] controller is not frequent in 8-bit computers. This had to be added due to the incapacity of the CRTC of generate video addresses. In fact, this part requires a DMA controller in order to operate. In the Datamaster the DMA controller is the Intel 8257 and also has a dedicated channel to floppy drive transactions.

The keyboard, precursor of the [[Model F keyboard|model F]], is based around the [[Intel MCS-48|Intel 8048]]. It communicates with an Intel 8255 through a parallel bus. The technology of the matrix is capacitive. It has 83 keys. During initialization, the computer expects the keyboard to send a verification code to announce its presence; the diagnostics fail otherwise.

The system includes a dedicated diagnostics port which assists repairs. This was used in conjunction with a probe that showed the corresponding step code; its usage was required when the machine failed to initialize the video subsystem.

=== Software ===
[[File:IBM_Datamaster_(2283391726).jpg|left|thumb|Diagnostics system of the System/23 Datamaster, displaying a ROM error (ROS 12h)]]
The Datamaster was conceived to be installed and operated without the need of specialists. For this reason it contained an embedded [[BASIC]] dialect. During the advanced stages of the project, IBM decided to fuse the extant BASIC implementation for the System/23 with the one from the [[IBM System/34|System/34]]. This decision delayed the development for around a year.<ref name="bradley199009">{{Cite magazine |last=Bradley, David J. |date=September 1990 |title=The Creation of the IBM PC |url=https://archive.org/stream/byte-magazine-1990-09/1990_09_BYTE_15-09_15th_Anniversary_Summit#page/n451/mode/2up |access-date=2025-11-08 |magazine=BYTE |pages=414–420}}</ref>  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]].<ref>{{Cite book |title=System/23 BASIC Language Reference |date=July 1981 |url=http://www.bitsavers.org/pdf/ibm/system23/user_manuals/binder_08/SA34-0109-1_BASIC_Language_Reference_Jul1981.pdf |publisher=IBM |access-date=2025-11-08 |language=en}}</ref> 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.<ref name=":3">{{Cite book |title=Diagnostic User Guide: System/32 with Diskette |date=1982 |url=https://bitsavers.org/pdf/ibm/system23/fe/6841631_System_23_Diagnostic_User_Guide_Apr82.pdf |publisher=IBM |pages=85–93}}</ref>

==Influence on later IBM systems==

The ease of the design team which was gained through the Datamaster and [[IBM Displaywriter System|Displaywriter]] projects influenced the decision to select an Intel CPU for their next microcomputer design. The delay caused by the decision to fuse both BASIC versions was the main lead to use [[Microsoft BASIC]] for the 5150 PC. Another of the reasons was due to the popularity of the latter.{{R|bradley199009}}

Many hardware components, specifically the 8253 timer and the 8259 interrupt controller, were reused in the later [[IBM Personal Computer|IBM PC]].<ref name="bradley199009"/> The DMA controller was replaced by the 8237, an improvement over the 8257 used in the System/23. The RAM memory width and parity check mechanism remained the same, though the memory type changed between projects. The same memory modules used in the Datamaster later appeared in the early official RAM expansions.<ref>{{Cite web |title=IBM 5150/5160 - Some IBM Expansion Cards and Options |work=IBM 51xx PC Family Computers |url=https://minuszerodegrees.net/5150_5160/cards/5150_5160_cards.htm |access-date=2025-11-08}}</ref> The computer's expansion bus, later known as the [[ISA bus]], was based in its Datamaster counterpart, with only five signals being changed.  Contrary to rumors, the Datamaster bus is not mirrored; it is a comprehension error caused by the service manual of the computer, which shows it mirrored.<ref name=":3"/>  The Datamaster's keyboard, which uses a similar layout as the [[IBM 5250|5251]], was reused in the PC, albeit with a [[serial interface]] instead of the original parallel one.{{R|bradley199009}}

Although not code-compatible, the diagnostics system was ported to the PC and simplified, and was renamed to POST.

== Emulators ==
[[File:IBM_Datamaster_MAME_prompt.png|left|thumb|IBM System/23 Datamaster in MAME. The system prompt waits for the user to start typing BASIC.]]
Until the end of February, 2025 this computer did not have an [[emulator]]. Since then, it counts with a [[MAME]] driver that offers an incomplete emulation, with one of its biggest limitations being the floppy subsystem. Nevertheless is functional enough to be used with BASIC.<ref>{{Cite web |title=MAME driver development thread |work=Forums |url=https://forums.bannister.org/ubbthreads.php?ubb=showflat&Number=123987#Post123987 |access-date=2025-04-17|language=en}}</ref> The work still needs to be approved into the main MAME repository.<ref>{{Cite web |title=MAME IBM System/23 driver pull request|website=[[GitHub]] |url=https://github.com/mamedev/mame/pull/13356 |language=en}}</ref>

{{Clear left}}

== Chronology ==
{{Timeline of the IBM Personal Computer}}

==References==
{{reflist}}

{{IBM personal computers}}

{{DEFAULTSORT:Ibm System 23}}
[[Category:IBM personal computers|2999System 23]]
[[Category:Computer-related introductions in 1981]]