https://rs-485.com/index.php?action=history&feed=atom&title=VAXBIVAXBI - Revision history2026-05-03T23:01:04ZRevision history for this page on the wikiMediaWiki 1.42.3https://rs-485.com/index.php?title=VAXBI&diff=1741&oldid=prevRS-485: Imported from Wikipedia (overwrite)2026-05-03T14:41:50Z<p>Imported from Wikipedia (overwrite)</p>
<p><b>New page</b></p><div>{{Short description|Bus for VAX computers}}<br />
{{More citations needed|date=November 2022}}<br />
{{Infobox Computer Hardware Bus<br />
| name = VAXBI<br />
| fullname = VAX Bus Interconnect<br />
| image = File:DEC-VAX-T1019-ECC-memory.jpg<br />
| caption = VAX [[Error-correcting code|ECC]] memory card with VAXBI interface highlighted<br />
| invent-date = {{Start date and age|1986}}<br />
| invent-name = [[Digital Equipment Corporation]]<br />
| super-name =<br />
| super-date =<br />
| width = 32<br />
| numdev =<br />
| speed =<br />
| style =<br />
| hotplug =<br />
| external =<br />
}}<br />
[[File:Locale_RS6_DEC-VAX-T1010-adapter.jpg|thumb|VAX BI to [[Unibus]] adapter.]]<br />
[[File:Locale_RS6_DEC VAX VAXBI T1034 DEBNT Ethernet and TK50 tape drive controller.jpg|thumb|Ethernet and tape drive controller]]<br />
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'''VAXBI''' ('''VAX B'''us '''I'''nterconnect) is a [[computer bus]] designed and sold by [[Digital Equipment Corporation]] (DEC), introduced in 1986.{{sfn|Di Giacomo|1990|p=4.4}}<br />
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The bus is an advanced, configuration-free synchronous bus used on DEC's later [[VAX]] computers.{{sfn|Di Giacomo|1990|p=4.9}} Like the [[Unibus]] and [[Q-Bus]] before it, it uses [[memory-mapped I/O]]{{sfn|Shah|1991|p=281}} but has 32-bit address and data paths. The VAXBI is a multiplexed bus with fully distributed arbitration and geographic addressing.{{sfn|Di Giacomo|1990|p=4.9, 4.19}}<br />
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All of the logic required to implement a VAXBI interface is contained within a single custom integrated circuit (the "BIIC") and the physical layout and [[printed wiring board]] layout for compliant [[Expansion card|cards]] is tightly specified, right down to the location of the dual amber status [[LED]]s that are required. The portion of the card that is reserved for the bus interface is referred to as "the VAXBI corner".<ref name="vaxbi-dn">{{cite book|url=http://bitsavers.org/pdf/dec/vax/vaxbi/EK-VBIDS-RM-001_VAXBI_Designers_Notebook_Jan86.pdf|title=VAXBI Designer's Notebook|publisher=Digital Equipment Corporation|date=January 1986}}</ref> VAXBI licensees were given the appropriate engineering drawings to allow them to exactly replicate a compliant card.<ref>{{cite journal | last=Wilson | first=David | date=March 1986 | url=https://link.gale.com/apps/doc/A6009840/GPS?u=wikipedia&sid=bookmark-GPS&xid=1610d58a | title=BI Bus Boosts Performance Of VAX Systems | work=Digital Design | publisher=UBM Information | volume=16 | issue=3 | pages=46–50 | via=Gale}}</ref>{{rp|50}}<br />
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VAXBI expansion cards mount into [[backplane]]s using a [[Zero insertion force|ZIF]] connector; depending on the backplane design, cards can be loaded from the top or the front side of the backplane. No cable connections are permitted on the cards; all connections are made via three uncommitted rows of backplane connectors. Similarly, no configuration jumpers are permitted on the cards; all setup is done by jumpers inserted on the backplane connectors or via software configuration.{{sfn|Di Giacomo|1990|p=4.9}}<br />
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Originally conceived by its engineers to be an [[Open standards|open]] bus, it was forced to be a tightly licensed bus by Digital's marketing and management, and was not nearly as successful as had originally been hoped for.<ref>{{cite journal | last=Simpson | first=David | date=December 21, 1992 | url=https://link.gale.com/apps/doc/A13063893/GPS?u=wikipedia&sid=bookmark-GPS&xid=ad4b588f | title=DEC, MTI end bitter licensing dispute | work=Digital News & Review | publisher= Reed Business Information | volume=9 | issue=24 | pages=1 ''et seq''. | via=Gale}}</ref><br />
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It is used in the [[VAX 6000]], [[VAX 8000]] (82xx, 83xx, 85xx, 87xx, 88xx models){{sfn|Shah|1991|p=2}} and the [[VAX 9000]] systems and also on the [[MIPS architecture|MIPS]] R3000 based [[DECsystem]] 5800 series.<br />
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A [[PDP-11]] implementation (the PDP-11/27) was envisioned but never advanced beyond the concept stage.<br />
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==References==<br />
{{reflist|colwidth=30em}}<br />
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===Works cited===<br />
* {{cite book | last=Di Giacomo | first=Joseph | date=1990 | url=https://archive.org/details/digitalbushandbo0000unse/ | title=Digital Bus Handbook | publisher=McGraw-Hill | isbn=9780070169234 | via=the Internet Archive}}<br />
* {{cite book | last=Shah | first=Jay | date=1991 | url=https://archive.org/details/vaxvmsconceptsfa0000shah/page/281/ | title=VAX/VMS: Concepts and Facilities | publisher=McGraw-Hill | isbn=0070563675 | via=the Internet Archive}}<br />
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==Further reading==<br />
* {{cite book|url=http://bitsavers.org/pdf/dec/vax/vaxbi/EK-VBISY-RM-003_VAXBI_System_Reference_Manual_Feb89.pdf|title=VAXBI System Reference Manual|publisher=[[Digital Equipment Corporation]]|date=February 1989}}<br />
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{{Computer bus}}<br />
{{Digital Equipment Corporation}}<br />
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{{DEFAULTSORT:Vaxbi Bus}}<br />
[[Category:Computer buses]]<br />
[[Category:DEC hardware]]<br />
[[Category:Computer-related introductions in 1986]]</div>RS-485