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PA-RISC SCSI

Bus variants

HP 9000 workstations and servers almost exclusively used the SCSI bus for their storage devices and harddrives. Many different variants of SCSI were developed for different usage scenarios and requirements. The below table lists some of these variants of the SCSI bus as found in PA-RISC computers.

SCSI buses in PA-RISC computers
Signalling: SE - Single-Ended, HVD - High-Voltage Differential, LVD - Low-Voltage Differential
SCSI Clock Width Data rate
(max)
Devices
(max)
Signals Length
(max)
Connector
Narrow SCSI 5 MHz 8-bit 5 MB/s 7 SE 6m 50-pin
Fast-Narrow SCSI 10 MHz 8-bit 10 MB/s 7 SE
HVD
3m
25m
50-pin
Fast-Wide SCSI 10 MHz 16-bit 20 MB/s 15 SE
HVD
3m
25m
68-pin
Ultra-Narrow SCSI 20 MHz 8-bit 20 MB/s 7 SE
LVD
HVD
1.5m
12m
25m
50-pin
Ultra-Wide SCSI 20 MHz 16-bit 40 MB/s 15 SE
LVD
HVD
1.5m
12m
25m
68-pin
Ultra2-Wide SCSI 40 MHz 16-bit 80 MB/s 15 LVD 12m 68-pin
Ultra160 SCSI 40 MHz 16-bit 160 MB/s 15 LVD 12m 68-pin
Ultra320 SCSI 80 MHz 16-bit 320 MB/s 15 LVD 12m 68-pin

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SCSI chipsets

HP 9000 workstations and servers from HP used several common SCSI controllers for their drives and storage. These chips were sometimes integrated into the mainboard or available on plug-in cards.

SCSI chipsets used in PA-RISC computers
Chipset Speed Width Data rate Bus
53C700 Narrow 5 MB/s GSC
53C710 Fast Narrow 10 MB/s GSC
53C720 Fast Wide 20 MB/s GSC
53C875 Ultra Wide 40 MB/s PCI
53C896 Ultra2 Wide 80 MB/s PCI

53C700

The 53C700 is the primary SCSI controller of the very early PA-RISC workstations with ASP chipset.

Features

Used in

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53C710

The NCR 53C710 is the primary SCSI controller used in early HP 9000s. It was integrated in the LASI chipset as a macrocell as well.

Features

Used in

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53C720

The NCR 53C720 was the secondary SCSI controller used in the early HP 9000s for the attachment of an Fast-Wide 16-bit SCSI-2 bus, utilizing HVD signalling. It was either controlled by the ASP2 chipset or interfaced to the GSC bus through a chip named Zalon.

Features

Used in

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53C875

The Symbios Logic/LSI 53C875 is the chip that provides the single Ultra-Wide SE SCSI channel on some of the newer PA-RISC workstations.

Features

Used in

References

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53C896

The Symbios Logic 53C896 SCSI ASIC is the chip used on some of the newer PA-RISC workstations and servers to control their storage I/O buses. This ASIC includes two 53C895-equivalent cores to control the two internal channels separately.

Features

Used in

References

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SCSI Adapters

SCSI adapters or HBAs for the various expansion buses found in PA-RISC systems.

EISA

SCSI adapters for the EISA bus.

EISA SCSI adapters for PA-RISC computers
Part SCSI type Signalling1 Boot HP-UX
A2679A Fast-Narrow SE no 9.0-11i/32-bit
25525A Fast-Narrow HVD 8.05-10.20
25525B Fast-Narrow HVD 8.05-11.0/32-bit

GSC

SCSI adapters for the variants of the GSC bus.

GSC SCSI adapters for PA-RISC computers
Part Formfactor SCSI type Signals Boot HP-UX
A2874-66005 EISA Fast-Wide HVD yes 9.05/11.0
A2969A HSC Fast-Wide HVD yes 10.01-11i
A3644A2 HSC Fast-Wide HVD 10.20-11i
A4107A EISA Fast-Wide HVD 9.05-11i/32-bit
A4268A GSC-M Fast-Wide HVD yes 9.05-11.0/32-bit

HP-PB

SCSI adapters for the HP-PB bus.

HP-PB SCSI adapters for PA-RISC computers
Part SCSI type Signals Boot HP-UX
27251A
28655A Fast-Narrow SE yes 10.01-11i
28696A Fast-Wide HVD yes 10.01-11i

PCI

SCSI adapters for the PCI bus.

PCI SCSI adapters for PA-RISC computers
Part SCSI type Signals Boot HP-UX
A4800A Fast-Wide HVD yes 10.2-11i
A4974A Ultra-Wide SE yes 10.20-11.0
A4976A Fast-Wide HVD yes 10.20-11.0
A4999A Ultra2-Wide LVD yes 10.20-11.0
A5159A Fast-Wide HVD yes 10.20-11i
  1. Signalling:
    • SE - Single-Ended
    • HVD - High-Voltage Differential
    • LVD - Low-Voltage Differential
  2. This card is only supported in the T-Class

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