SCSI SE High Performance Internal/External I/O Controller (4-1)

SCSI I/O Controller 4-1
Term Power Overload Protection


  • Accepts multiple commands per device SCSI chain
  • SCSI burst 4.0MB per second (synchronous) SCSI-1 transfer
  • SCSI initiator (command issuer)
  • SCSI parity support (Ed. IBM standard)
  • One adapter per system (Ed. Software issue?)
  • Micro Channel Interface
    • 4-byte (32-bit) Bus Master
    • Streaming data support (Ed. Good for a SCSI-1 adapter)
    • Address and data parity support
  • Interrupt levels 3, 4, 5, 7, 10, 11, 12, 14

SCSI I/O Controller 4-1 Adapter ID 8D77, FRU P/N 31G9729, FC 2828

D1 Diode
DL1,2 PE 23111 Delay Line
F1 1 A / 125 V Littelfuse (fast blow)
J1 High Availability Jumper
J2 Mini-C60 SCSI port
U1,5 CXK58257AM-12L 32Kx8 SRAM
U2 31G9727 SCSI BIOS?
U3 31G9725 SCSI BIOS?
U11 80C186-16
U13 31G9723
U17 81F8929(ESD)
U36 WD33C93A
Y1 31.9500 MHz osc
Y2 39.95 MHz osc

No components on the solder side.

J1 (also called P3) High Availability Jumper

Must be out of the circuit for high availability ("Y") configuration. Put the jumpers over one row only so you don't loose them. There are 13 pairs of pins. You will need a 6 and 7 pair berg jumper (ganged jumper) in order to use this for normal SCSI configuration.

Term Power Overload Protection

The SCSI controller provides term power for the SCSI bus; connect devices to the bus so they do not provide term power. The controller uses a fuse that must be replaced after failure.

Do not connect or disconnect any SCSI device while power is on. Such "hot plugging" is forbidden because this practice may blow the controller fuse, corrupt data or permanently damage SCSI controller chips in controllers or devices.

The fuse on an SCSI controller protects the external and internal SCSI bus. The fuse may be blown by a defective cable, terminator, or device attached to the controller, but not by a defective controller.

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Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

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Last update: 08 May 2024 - Changelog | About | Legal & Contact