Editing IBM PS/2 Model 60 (section)

== Architecture ==

The Model 60 planar uses an Intel 80286 at 10 MHz with the IBM PS/2 Model 50/60 chipset family. The planar carries:

* '''CPU''': Intel 80286 in a 68-pin PGA socket, 10 MHz, 1 wait state to memory (the same 125-ns DRAM throughout the Model 60's life — IBM never gave the Model 60 the 85-ns DRAM upgrade that made the [[IBM PS/2 Model 50|Model 50]] into the Z).
* '''Math coprocessor''': Intel 80287 socket adjacent to the 80286. Optional.
* '''MCA bus''': '''Eight MCA slots''' total. One is 8-bit MCA (for legacy 8-bit MCA cards); the other seven are 16-bit MCA. No 32-bit MCA slots; no ISA compatibility.
* '''Integrated VGA''' on the planar with the IBM VGA gate-array implementation and an Inmos IMSG171P-style RAMDAC. Modes: 80×25 / 80×50 text, 640×480×16, 320×200×256, 720×400×16 text (8×16 character box). Output on 15-pin DSUB at rear. Analog monitors only.
* '''Integrated I/O''':
** PS/2 keyboard (Mini-DIN-6).
** PS/2 pointing-device port (Mini-DIN-6).
** Asynchronous serial (DB-25 male).
** Centronics parallel (DB-25 female).
* '''Floppy controller''': PS/2 single-cable interface integrated on the planar, 1.44 MB 3.5" half-height drive.
* '''Hard drive interface''': '''None on the planar''' — the hard drive is supplied through an MCA controller card. The drive plugs directly into a connector on the rear edge of the controller card, eliminating a separate ribbon cable to the planar. The 8560-041 uses the '''IBM Fixed Disk Adapter/A''' (ST-506); the 8560-071 uses the '''IBM ESDI Fixed Disk Adapter/A'''.
* '''BIOS''': 128 KB total, split between CBIOS (DOS-compatible) and ABIOS (OS/2 protected-mode). Two 64 KB EPROM / mask-ROM chips at U-positions.
* '''CMOS / RTC''': Battery-backed via the Motorola MC146818 RTC on early Model 60 units (with a discrete external 4×AA battery pack feeding the planar via a 4-pin header), or the Dallas DS1287 / DS12887 integrated module on later production units.

=== Memory subsystem ===

The Model 60 has '''four 30-pin PS/2 SIMM sockets''' on the planar, each accepting 256 KB parity SIMMs (1 MB on planar standard, 4 × 256 KB). Additional RAM is provided via MCA memory cards, with the system maximum at '''7 MB'''. SIMMs are IBM PS/2-pinout 125-ns parity.

=== Storage ===

* '''Floppy''': 1.44 MB 3.5" half-height, PS/2 single-cable interface.
* '''Hard drive (8560-041)''': 44 MB Seagate ST-506-class drive on the IBM Fixed Disk Adapter/A.
* '''Hard drive (8560-071)''': 70 MB Maxtor / Miniscribe / Western Digital ESDI drive on the IBM ESDI Fixed Disk Adapter/A.

Additional drives can be fitted in the four-bay drive cage; the Model 60 supports up to two hard drives plus a 5.25" full-height device (often a tape drive).

=== Chassis ===

The Model 60 chassis is a floor-standing tower, 597 H × 166 W × 482 D mm, weighing 21.3 kg (47 lb). The same tower chassis is used by the [[IBM PS/2 Model 80]] and the later Model 65 SX. The drive cage runs vertically up the front; the MCA cards plug into the riser on the left side; the planar mounts on the floor; the PSU sits at the top.

The tower introduced PC-class machines to the floor-standing form factor and inspired competitors to follow within 12 months.

=== Power Supply ===

* '''207 W''' (8560-041) — sufficient for ST-506-equipped machines.
* '''225 W''' (8560-071) — uprated for the higher-current ESDI drive.

Both PSUs are 110/220 VAC auto-sensing with auto-restart. PS/2 single-cable drive power feed — '''no Molex 4-pin connectors'''.

The Model 60 PSU is '''not''' interchangeable with the Model 50 PSU (different planar connectors). It '''is''' interchangeable with the Model 80 PSU in the same chassis.