TURBOchannel

TURBOchannel is an open computer bus developed by DEC by during the late 1980s and early 1990s.

Digital abandoned the use of TURBOchannel in favor of the EISA and PCI buses in late 1994, with the introduction of their AlphaStation and AlphaServer systems.

Digital initially expected TURBOchannel to gain widespeard industry acceptance due to its status as an ARC standard, although ultimately Digital was the only major user of the TURBOchannel in their own DEC 3000 AXP, DECstation 5000 Series, DECsystem and VAXstation 4000 systems.

[2] In the early 1990s, Digital expected the TURBOchannel bus to face serious competition from other buses from other vendors such as HP, Sun and IBM, and therefore it announced that it intended to update the existing TURBOchannel specification to permit it to transfer up to 200 MB/s, using similar hardware.

This upgrade to the protocol was to be backwards compatible, but Digital later canceled the intended update and TURBOchannel itself towards the end of 1994 once it became clear that PCI had become dominant.

TURBOchannel is a 32-bit address and data multiplexed bus, clocked at frequencies between 12.5 and 25 MHz, with a maximum theoretical usable bandwidth of 90 MB/s.

The firmware contained within TURBOchannel cards is MIPS machine code, a remnant of the bus' original use in MIPS-based systems.

The three possible schemes were divided into a low-cost, a mid-range and high performance system implementations.

A TURBOchannel Extender box is used to reduce the number of slots required inside a system for double and triple width options.