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IBM PS2 SCSI-A Technical Reference

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The IBM PS/2 SCSI Adapter/A Technical Reference, First Edition (March 1990), is IBM's 96-page programming reference for the PS/2 Micro Channel SCSI adapter.

What it contains

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  • Description and Adapter Components — the adapter microprocessor, the SCSI bus controller, the data flow controller, the adapter BIOS and POST, and the system interface / bus master DMA controller.
  • Statement of Conformance — the level of SCSI conformance, the alternatives and options implemented, the devices and SCSI commands supported, the SCSI messages supported, and the device requirements for POST support (which is the section that explains why a given drive is or is not seen at power-on).
  • Programmable Option Select — POS registers 0 to 4 (hex 0100–0104), which are what the Reference Diskette writes when it configures the card.
  • Adapter-to-system interface — the command interface registers (hex 00–03), attention register (hex 04), basic control register (hex 05), interrupt status register (hex 06) and basic status register (hex 07).
  • Command and status blocks — Command Complete Status Block, Get POS and Adapter Information, Read Data, Read Device Capacity and the rest of the command set.

What it does not contain

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A programming reference, not a service document: no FRU numbers, no removal procedure, no schematic and no component values. It does not cover the SCSI cables or terminators, which are in the machine-specific hardware maintenance pamphlets.

What it settles

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Device requirements for POST support settles the common complaint that a perfectly good SCSI disk is invisible to a PS/2 at power-on: IBM lists the conditions a device must meet before the adapter BIOS will enumerate it during POST.

Download it here: IBM PS2 SCSI-A Technical Reference.pdf

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