IBM System/23 Datamaster - Revision history

Retroand: Changed status of machine in collection

2025-09-19T07:53:38Z

Changed status of machine in collection

← Older revision		Revision as of 07:53, 19 September 2025
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	\|5324		\|5324
	\|124		\|124
	\|French, in restoration, no keyboard, no monitor		\|French, in restoration, with American keyboard, no monitor
	\|}		\|}

Retroand: Added referenced statement about lower spec submodels being retired by 1982

2025-08-06T07:50:50Z

Added referenced statement about lower spec submodels being retired by 1982

← Older revision		Revision as of 07:50, 6 August 2025
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	The absence of a submodel comprising a word-processing card and an amount of RAM of 32KB is due that IBM set the specifications for the word processing units with a minimum of 64KB.		The absence of a submodel comprising a word-processing card and an amount of RAM of 32KB is due that IBM set the specifications for the word processing units with a minimum of 64KB.
	The submodel must be determined not by the number written at the rear plate but by observing the features of the machine, as some plates don't have the submodel written or have dummy values.		The submodel must be determined not by the number written at the rear plate but by observing the features of the machine, as some plates don't have the submodel written or have dummy values.
			By late 1982, most submodels with 32KB and 31SD floppy drives had been withdrawn from the market.<ref>https://archive.org/details/bitsavers_ibmserviceceForConsultants198210_13344165/page/n69/mode/2up</ref>

	== Hardware Description ==		== Hardware Description ==

Retroand: Added unit in collection

2025-08-05T10:23:44Z

Added unit in collection

← Older revision		Revision as of 10:23, 5 August 2025
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	\|124		\|124
	\|American, boards only, fitted with 32KB RAM, no keyboard		\|American, boards only, fitted with 32KB RAM, no keyboard
			\|-
			\|
			\|5324
			\|124
			\|French, in restoration, no keyboard, no monitor
	\|}		\|}

Retroand: Added table of submodels

2025-08-05T07:20:16Z

Added table of submodels

@@ Line 38: / Line 38: @@
 === Creation of the IBM PC ===
 It is often said that the IBM had a rushed development of the PC with a single year in development. Whereas the statement is partially true, it is also forgotten how close both systems are and how the same engineers that worked in the Datamaster later worked in the PC, bringing the required expertise. Also, the chosen CPU was the [[Intel 8088]] due of its similarity hardware-wise with the [[Intel 8085]] and this way most of the peripherals were maintained in the transition from the Datamaster. The character set and its format were also brought from the System/23 to the [[5150]]. Also, the expansion bus is nearly untouched in that evolution. Finally, from pictures of early prototypes it can be seen that the power connectors were the same as the one in the Datamaster. As a conclusion, it might be stated that the early life of the IBM PC started as modifications on the Datamaster.
 == Hardware Description ==

Retroand: Added description for the video subsystem

2025-07-09T07:56:51Z

Added description for the video subsystem

← Older revision		Revision as of 07:56, 9 July 2025
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	=== Video Subsystem ===		=== Video Subsystem ===
			[[File:Datamaster_Video_Connector.png\|260px\|thumb\|left\|alt=Datamaster video connector\|Datamaster video connector]]
	The video subsystem is almost copied verbatim from the Intel 8275 Datasheet. It consists in a 8275 variant plus a 8257 DMA device. The 4178629 made by Intel is the CRTC chip and it behaves exactly the same way as stock 8275s. Compatibility with stock 8275 has been tested with good results, as well as the Soviet KR580VG75, which is also compatible. The Intel 8276 is not compatible without a ROM hack that modifies test 05h in order to deactivate the light pen test.		The video subsystem is almost copied verbatim from the Intel 8275 Datasheet. It consists in a 8275 variant plus a 8257 DMA device. The 4178629 made by Intel is the CRTC chip and it behaves exactly the same way as stock 8275s. Compatibility with stock 8275 has been tested with good results, as well as the Soviet KR580VG75, which is also compatible. The Intel 8276 is not compatible without a ROM hack that modifies test 05h in order to deactivate the light pen test.

			The video connector present in the motherboard presents at least two supply voltages (+5V and +12V). The other video signals are strictly TTL compatible. Synchronism signals are separate, vertical sync is negative and horizontal sync is positive. The display has three degrees of monochrome tones: full off, normal and highlighted (full on). This is achieved with an intensity signal being carried separately from the video signal.

			The Datamaster has two pixel clocks: 18.432 MHz for the American units and 18.2 MHz for the European machines. Its timings makes them incompatible with the later and more common MDA. While European units have both oscillators and the selection jumper, the Americans only have an oscillator and lack the jumper, although its space on board is present.

			There have been unofficial attempts to obtain the picture without having to recur to the original monitors. For instance, a composite video addon was first created, followed by a much simpler and overall better RGB-Scart adapter. Finally, the computer has been given support by the RGBtoHDMI project, therefore enabling Datamasters with broken or no monitor at all to be able to output image.

	=== Diagnostics port ===		=== Diagnostics port ===

Retroand: Added unit in collection

2025-07-01T08:41:46Z

Added unit in collection

← Older revision		Revision as of 08:41, 1 July 2025
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	! Inventory ID !! Model !! Submodel !! Comments		! Inventory ID !! Model !! Submodel !! Comments
	\|-		\|-
	\| 22 \|\| 5322 \|\| 124 \|\| ~~Fitted~~ with ~~64KB~~ RAM + 2 x 8" floppy drives		\| 22 \|\| 5322 \|\| 124 \|\| Spanish, fitted with 96KB RAM + 2 x 8" floppy drives
			\|-
			\|
			\|5322
			\|124
			\|American, boards only, fitted with 32KB RAM, no keyboard
	\|}		\|}

Retroand: Added link to Q&A with Dr. Bradley

2025-07-01T06:06:12Z

Added link to Q&A with Dr. Bradley

← Older revision		Revision as of 06:06, 1 July 2025
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	== See also ==		== See also ==
	[[IBM System/23 Datamaster Resources]]		[[IBM System/23 Datamaster Resources]]

			[[Q&A with Dr. Dave Bradley]]
	== References ==		== References ==
	<references />		<references />

Retroand: Added floppy disk controller ports

2025-05-11T10:22:32Z

Added floppy disk controller ports

← Older revision		Revision as of 10:22, 11 May 2025
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	The Datamaster has a rich set of Intel peripherals which consist of a 8251 USART, 8253 PIT, three 8255 PPI, 8257 DMA, 8259 PIC and 8275 CRTC. All of them, including other devices are accessed using the following ports<ref name=":0" />:		The Datamaster has a rich set of Intel peripherals which consist of a 8251 USART, 8253 PIT, three 8255 PPI, 8257 DMA, 8259 PIC and 8275 CRTC. All of them, including other devices are accessed using the following ports<ref name=":0" />:
	{\| class="wikitable"		{\| class="wikitable"
			\|+ I/O Ports decoded in the motherboard

	! Ports !! Device !! Function		! Ports !! Device !! Function
	\|-		\|-
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	\|-		\|-
	\| 4Fh \|\| 8255#3 \|\| 8255#3 control port		\| 4Fh \|\| 8255#3 \|\| 8255#3 control port
			\|}

			{\| class="wikitable"
			\|+ I/O Ports decoded in the floppy controller card
			! Ports !! Device !! Function
			\|-
			\| F4h-F7h \|\| NEC 765 \|\| Floppy drive controller
			\|-
			\| F8h-FBh \|\| 8255 PPI \|\| Unknown purpose
	\|}		\|}

Retroand: /* Diagnostics */

2025-05-05T07:25:49Z

Diagnostics

← Older revision		Revision as of 07:25, 5 May 2025
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	\| 04 \|\| RAM \|\| Test for the first unpaged 16KB. Lecture of register 0x2e.		\| 04 \|\| RAM \|\| Test for the first unpaged 16KB. Lecture of register 0x2e.
	\|-		\|-
	\| 05 \|\| CRTC, DMA \|\| Interrupt test; initialization of 8275, 8257; light pen test~~. It fails with standard 8275s~~.		\| 05 \|\| CRTC, DMA \|\| Interrupt test; initialization of 8275, 8257; light pen test.
	\|-		\|-
	\| 06 \|\| CRTC \|\| Sync and video data tests.		\| 06 \|\| CRTC \|\| Sync and video data tests.

Retroand: /* Interrupts */

2025-05-05T07:25:10Z

Interrupts

← Older revision		Revision as of 07:25, 5 May 2025
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	\| RST7.5 \|\| PIT timer 2		\| RST7.5 \|\| PIT timer 2
	\|-		\|-
	\| RST6.5 \|\| ~~Unknown~~		\| RST6.5 \|\| Expansion slot B4
	\|-		\|-
	\| RST5.5 \|\| 8275 IRQ (if J1 is bridged)		\| RST5.5 \|\| 8275 IRQ (if J1 is bridged)