IBM PC XT/370
 | |
| The PC/370-P processor card of an XT/370, with the Diagnostics/370 Personality diskette | |
| Specifications | |
|---|---|
| Manufacturer | IBM |
| Type | Desktop personal computer with System/370 processor cards |
| Released | October 1983 |
| Discontinued | April 1987 |
| Intro price | US$8,085 (Model 588, Fall 1984) |
| CPU | Intel 8088 at 4.77 MHz (PC side); two Motorola 68000s, one with IBM microcode, and a modified Intel 8087 (System/370 side) |
| Memory | 640 KB in PC mode; 480 KB of System/370 storage in VM/PC mode; up to 4 MB virtual |
| Storage | One 360 KB diskette drive; one 10 MB fixed disk (Model 588), or two in a 5161 Expansion Unit (Model 568) |
| Display | IBM 5151 monochrome display (5153 colour optional) |
| Sound | — |
| OS / Firmware | PC DOS 2.10 with VM/PC |
| Predecessor | IBM PC XT (5160) |
| Model no. | 5160 models 568, 588 and 589 |
The IBM PC XT/370 is an IBM PC XT (5160) fitted with cards that execute IBM System/370 instructions, sold as 5160 models 568, 588 and 589. IBM announced it in October 1983.[1] It can work as an ordinary XT, as an IBM 3277 display terminal attached to a mainframe, or as a single-user System/370 running VM/PC, and a hot key switches between them.[2] IBM withdrew the XT/370 and the AT/370 in April 1987.[3]
IBM's service manual describes it as "an extended version of the 5160 XT with 256Kb of memory on the system board".[4]
History
[edit | edit source]BYTE's autumn 1984 price list gave US$8,085 for the Model 588, with one diskette drive and one fixed disk, and US$6,230 for the Model 568, which has no fixed disk and needs the XT/370 expansion unit. The VM/PC program was US$1,000.[5] The XT/370 came with a monochrome display and adapter; a colour monitor could be used, but not its colour or graphics in terminal or 370 mode.[2] An existing XT or IBM PC could be converted with the XT/370 Option Kit, feature 3891, which included a new nameplate; the machine needed 256 KB on the system board.[2]
Sabine's review in the same issue called the XT/370 "a qualified success".[2] A market forecast in the issue took IBM's claim of 0.1 MIPS for work that fits in physical memory, and argued that paging to the XT's fixed disk would pull real performance well below that.[6] When IBM withdrew it, Computer Business Review described the design as "two Motorola 68000s, one of them custom-microcoded, and an Intel 8087".[3]
The XT/370 cards
[edit | edit source]IBM's feature chart lists the cards against the models:[4]
| Model | Memory on system board | Diskette | Fixed disk | PC/370-P | PC/370-M | PC/3277-EM |
|---|---|---|---|---|---|---|
| 568 | 256 KB | 1 full-height | none | yes | yes | yes |
| 588 | 256 KB | 1 full-height | 10 MB | yes | yes | yes |
| 589 | 256 KB | 1 full-height | 10 MB | yes | yes | no |
| Card | IBM FRU | Slot | Function |
|---|---|---|---|
| PC/370-P (processor) | 8654372 | 4 | Executes System/370 instructions |
| PC/370-M (memory) | 8654371 | 3 | 512 KB of parity-checked RAM shared by the PC and the 370 processor |
| PC/370-P-M cable | 8654374 | Connects the processor and memory cards | |
| PC/3277-EM | 8654373 | 3277 Model 2 terminal emulation over coaxial cable |
Slots from IBM's XT/370 pages; FRU numbers from IBM's parts list.[4]
IBM's service manual lists a Remote Display Terminal Device Emulation Adapter (which can go in slot 2) and the IBM 3278/79 Emulation Adapter as options, and notes that older machines might contain the PC/3277-EM card.[4] BYTE counted the 3277 emulation card as the third standard board in 1984.[2]
PC/370-P
[edit | edit source]The processor card carries two Motorola 68000s and a modified Intel 8087. One 68000 fetches and decodes instructions and emulates most System/370 fixed-point instructions, using its own registers for the 370's general registers and program status word. The other handles the 370 page table, exceptions, and system instructions such as SVC and DIAGNOSE, which on the XT/370 passes requests from the 370 side to PC DOS. The 8087 executes the 370 floating-point instructions. The card holds a page table of 1,024 entries of 4 KB, giving a 4 MB virtual address space.[2] BYTE's specification box describes one 68000 as standard and the other as a custom IBM/Motorola part.[5]
PC/370-M
[edit | edit source]The memory card holds 512 KB of parity-checked RAM, usable by either the PC/370-P or the XT.[4] The 8088 sees it from 256 KB upwards with the top 128 KB mapped out, which brings the PC side to 640 KB. The 370 processor sees the first 480 KB as System/370 storage; the remaining 32 KB holds the 68000 microcode for the 370 functions and the PC DOS interface. The 8088 has priority over the processor card, and this memory is slightly slower than the system board's, so the XT/370 runs a little slower than a plain XT in PC mode.[2] The BYTE forecast in the same issue uses 416 KB for the 370 processor's physical memory.[6]
Fixed disk configurations
[edit | edit source]The Model 588 has one 10 MB fixed disk in the system unit. The Model 568 has none; for 20 MB it is used with a 5161 Model 3 expansion unit holding two fixed disks.[2][4] On the 20 MB XT/370, the extender card switches must be set for 608 KB to 640 KB.[4]
Specifications
[edit | edit source]IBM's figures for the XT/370 system unit:[4]
| Item | Value |
|---|---|
| Height | 142 mm (5.5 in) |
| Length | 500 mm (19.6 in) |
| Depth | 410 mm (16.1 in) |
| Weight | 14.5 kg (32 lb) |
| Power cable | 1.83 m (6 ft), 18 AWG |
| Air temperature, system on | 15.6 to 32.2 °C (60 to 90 °F) |
| Humidity, on / off | 8–80 % / 20–80 % |
| Heat output | 650 BTU/hr |
| Noise | 49.5 dBA, system unit with monochrome display and expansion unit |
| Electrical | 104–127 V AC, 120 V nominal |
| Keyboard | 57 × 500 × 200 mm, 2.9 kg |
VM/PC
[edit | edit source]VM/PC runs as a PC DOS application and gives the user a single-user system with the characteristics of VM/SP Release 3. On the XT/370 it requires PC DOS 2.10, supports only 360 KB diskettes and manages a virtual memory of up to 4 MB. It supports a 3270 coaxial connection or an RS-232 3101 connection to a host; with the 3277-2 Device Emulator Adapter, available only with the XT/370, the machine emulates a 3277-2; with the 3278/79 Emulation Adapter it emulates a 3278-2.[7]
CMS minidisks are ordinary DOS files named after the owner and the minidisk address, so the CMS 100 disk supplied with VM/PC is C:CMS.100. A minidisk can be as large as the 10 MB fixed disk, or up to 354 KB on a diskette. The IMPORT and EXPORT commands move files between CMS and PC DOS.[7][2]
Documentation
[edit | edit source]- IBM Personal Computer Family Service Information Manual: IBM's 1989 service manual, with the XT/370 pages, feature chart and parts.
- VM/PC User's Guide (December 1984).
- IBM PC XT 5155 5160 Technical Reference (March 1986) for the XT system board and supply.
Related pages
[edit | edit source]- IBM PC XT/370 Maintenance Guide
- IBM PC XT/370 Troubleshooting Guide
- IBM PC XT/370 Capacitor Replacement Guide
- IBM PC XT (5160)
- IBM 3270 PC
- IBM 5100 and IBM PALM processor, IBM's earlier desktop machines able to run mainframe software
References
[edit | edit source]- ↑ Paul E. Hoffman and G. Mack Hicks, "XT/370: The Missing Link", BYTE Guide to the IBM PC, Fall 1984 (archive.org item byte-magazine-1984-09), p. 212: "IBM's announcement of the XT/370 last October".
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Ernest Sabine, "The IBM XT/370 Personal Computer", BYTE Guide to the IBM PC, Fall 1984, pp. 210–211 (archive.org item byte-magazine-1984-09). The three modes, model numbers, option kit feature 3891, the three boards and their slots, the processor card's chips and their division of work, the 1024-entry page table, and the PC/370-M memory mapping.
- ↑ 3.0 3.1 "IBM Gives Up on the Personal XT/, AT/370", Computer Business Review, 13 April 1987, online at techmonitor.ai.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 IBM, Personal Computer Family Service Information Manual, SA38-0037-00, First Edition, January 1989, hosted as File:IBM Personal Computer Family Service Information Manual SA38-0037-00.pdf and described at IBM Personal Computer Family Service Information Manual. Chapter 6: 5160 model feature chart (p. 6-2); extender card switches for the 20 MB XT/370 (p. 6-14); "5160 XT/370" (pp. 6-17 to 6-19), with the card complement and slots, options, fixed disk configurations, specifications and card descriptions. Chapter 18, p. 18-19: XT/370 parts.
- ↑ 5.0 5.1 "IBM Personal Computer XT/370", in "IBM Personal Computers at a Glance", BYTE Guide to the IBM PC, Fall 1984, pp. 19–20. Specification box and prices.
- ↑ 6.0 6.1 "The XT/370", in a product forecast, BYTE Guide to the IBM PC, Fall 1984, pp. 35–36. IBM's 0.1 MIPS claim, 416 KB of physical memory for the 370 processor, about US$12,000 per workstation, and the effect of disk paging.
- ↑ 7.0 7.1 IBM, Virtual Machine/Personal Computer User's Guide, First Edition, December 1984, hosted as File:IBM VM-PC User's Guide (December 1984).pdf. VM/SP Release 3 characteristics and 4 MB virtual memory (p. 1-1); DOS 2.10, 360 KB diskettes and 10 MB fixed disks on the XT/370 (p. 1-3); 3277-2 and 3278/79 emulation (p. 1-4); virtual machine and minidisk sizes (pp. 2-19 to 2-20); minidisk file names (p. 3-18).