SCSI controller: Difference between revisions
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*[https://en.wikipedia.org/wiki/SCSI Wikipedia SCSI] |
*[https://en.wikipedia.org/wiki/SCSI Wikipedia SCSI] |
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*[https://en.wikipedia.org/wiki/SCSI_host_adapter Wikipedia SCSI host adapter] |
*[https://en.wikipedia.org/wiki/SCSI_host_adapter Wikipedia SCSI host adapter] |
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*[https://everything2.com/title/SCSI+Terminator] |
*[https://everything2.com/title/SCSI+Terminator SCSI terminator info] |
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Revision as of 02:19, 6 March 2023
SCSI controller
Introduction
The SCSI bus is a system to connect devices to computers. Devices means: harddiscs, scanners, graphic tablets, storage systems and media drives, e.g. ZIP drives, JAZ drives, magneto-optical (MO) drives, bernoulli discs and many more. It is designed as an extension of the systembus into the "outer world" but is used to install internal drives too. The SCSI technology had its prime time in the years 1985 - 2005. There are many types of speed and connection protocols - most of them are backward compatible. Nowadays it has been superseeded by SATA and USB protocols.
However, for RISC PC and Archimedes computers it could be a useful way to connect the machine with peripherals. Newer machines (Raspberry Pi, Titanium, BeagleBoard, ARMini) often dont allow to connect a SCSI adapter - and should use the newer types of peripheral connectivity.
To install a SCSI system at least one device is needed that connects to a host adapter (installed in the computer) by a (parallel) cable. The SCSI connection has to be terminated at both ends of the cable. Therefore a so called terminator needs to be installed, especially on older devices and host adapters. Newer devices often come with a jumper to switch the termination on/off (e.g. at ZIP drives). SCSI host adapter sometimes come with the ability to measure the need for termination and can auto-terminate their endpoint of the connection.
Controller
A so called SCSI controller is the host bus adapter that has to be installed into the computer. There are many different controllers available, some of them produced by Acorn but the most are third party. There are older 8 bit SCSI controllers, normal 16 bit and newer fast 32 bit wide host bus adaptors that are able to use DMA (in the first two podule slots of an RISC PC). Some of them are normal podules, but other came as proprietory add-on cards (HCCS) or in unusual ways of interconnect (VerticalTwist).
This list tries to give an overview of all available SCSI controllers for RISC OS computers, ever.
Acorn
This is the "original" design - and came in three different variants, as AKA30, AKA31, AKA32.
These cards have to be terminated by external and internal resistors networks. There had been an official internal terminator, but other models work as well.
Owl
Morley
Vertical Twist
HCCS
ACE
ACE / MCS of Dortmund (Germany) made some interfaces for RISC OS computers, one of them had been the ACE SCSI controller named SCSI Connect. It allows 16 bit (Archimedes) or 32 bit (RISC PC) connections and establishes a Fast-SCSI-2 connection. It comes with internal 50pol and external 50pol half-pitch connectors.
Power-tec (of Gary Partis)
The Power-tec Card is available as 16 bit SCSI-2 host bus adapter for the RISC PC and A5000, A540 computers. A smaller and slower SCSI-1 card is available for the 8 bit slots in A3000 and A3010. A305, A310, A440 computers need to be upgraded to MEMC1A to reach the full speed of the Card. RISC PC computers should have at least 1MB VRAM, otherwise the card slows done a bit. To achieve the faster DMA data transfers a RISC PC is needed, the SCSI card should be installed into the podule slot 1. Only slot 0 and slot 1 are DMA capable.
These cards come with an impressive toolset of software wich eases the installation and configuration of the scsi devices. Formatting and BackUp tools are included as well as a programm to flash the onboard Flash-Eprom with newer versions of the cards own software. These cards are able to handle most of the disk formats and the partitioning schemes of the other cards but its a good idea to use the cards own formatting tools. Its possible to install more than one of these cards in a computer. No more active development but a support scheme is available at Partis Computing.
Device connectors are 50pol internal and 50pol half-pitch external.
