- TURBOchannel
TURBOchannel is an open
computer bus developed by DEC by during the late 1980s and early 1990s. Although it was open for any vendor to implement in their own systems, it was mostly used in Digital's own systems such as the MIPS-basedDECstation andDECsystem systems, in the VAXstation 4000, and in theDEC Alpha -basedDEC 3000 AXP . Digital abandoned the use of TURBOchannel in favor of the EISA and PCI buses in late 1994, with the introduction of theirAlphaStation andAlphaServer systems.History
TURBOchannel was developed in the late 1980s by Digital and was continuously revised through the early 1990s by the TURBOchannel Industry Group, an industry group set up by Digital to develop promote the bus. TURBOchannel was an open bus from the beginning, the specification was and publically available at an initial purchase cost for the reproduction of material for third-party implementation, as were the mechanical specifications, for both implementation in both systems and in options. TURBOchannel was selected by the failed ACE (Advanced Computing Environment) for use as the industry standard bus in ARC (Advanced RISC Computing) compliant machines. 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. While no third-parties implemented TURBOchannel in systems, they did implement numerous TURBOchannel option modules for Digital's systems.Although the main developer and promoter of TURBOchannel was the TURBOchannel Industry Group, Digital's TRI/ADD Program, an initiative to provide technical and marketing support to third-parties implementing peripherals based on open interfaces such as FutureBus+, SCSI, VME and TURBOchannel for Digital's systems, was also involved in promoting TURBOchannel implementation and sales. [TRI/ADD Program Shippable Products Catalog, September 1991, Revision 5.0, Digital Equipment Corporation.] The TRI/ADD Program was discontinued on 15 December 1992, except for in Japan. [TRI/ADD Program Shippable Products Catalog, Revision 21.0, January 1993, Digital Equipment Corporation.]
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.
Architecture
TURBOchannel is a 32-bit address and data
multiplexed bus, clocked at frequencies between 12.5 to 25 MHz, with a maximum theoretical usable bandwidth of 90 MB/s. The bus however differs from others at the time by having point to point control lines. The firmware contained within TURBOchannel cards is MIPSmachine code , a remnant of the bus' original use in MIPS-based systems. Because of this, later systems that used this bus such as the Alpha-basedDEC 3000 AXP used anemulator contained in its system firmware to properly initialize them.Signals
ee also
*
List of device bandwidths References
* TURBOchannel Hardware Specification, EK-369AA-OD-007B, January 1993, Digital Equipment Corporation.
External links
* [ftp://ftp.hp.com/ftp1/pub/alphaserver/archive/triadd A collection of archived documents from the defunct TURBOchannel Industry Group. Contains the entire TURBOchannel specification.]
* [http://www.tobycreek.org/computers/alpha.html Shows interior of a computer using the TURBOchannel bus]
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