https://gunkies.org/index.php?action=history&feed=atom&title=Standard_Drive_BusStandard Drive Bus - Revision history2026-09-28T07:53:25ZRevision history for this page on the wikiMediaWiki 1.43.9https://gunkies.org/w/index.php?title=Standard_Drive_Bus&diff=34195&oldid=prevJnc: +Categories2024-04-19T10:59:35Z<p>+Categories</p>
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<p><b>New page</b></p><div>The '''Standard Drive Bus''' (sometimes referred to by the acronym, '''SDB''') is the lowest, [[hardware]] level of several [[Digital Equipment Corporation|DEC]] designed [[mass storage]] [[drive]] to [[device controller|controller]] interfaces. It is a key element of the [[Digital Storage Architecture]] (DSA), used with [[PDP-11]]s and with [[VAX]] single and multiple [[Central Processing Unit|CPU]] systems.<br />
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A new standard, it was introduced (in 1981) because no existing standard had the capabilities that DEC deemed necessary in the mass storage arena. It is part of the [[Standard Disk Interconnect]] and [[Standard Tape Interconnect]]; both add higher layer [[protocol]]s which are adapted to the needs of their supported device types.<br />
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The SDB drive to controller interconnect is a [[serial]] link which connects each drive directly (i.e. individually), or 'radially' (a term for such a device connection approach which DEC also used in its early machines), to its controller. <br />
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Electrically, the SDB consists of four signal carriers, using small-diameter [[coaxial cable]]s; two for moving user data, commands, and responses between drive and controller, and two for continuous real time transmission of drive and controller status information. The SDB signals are [[transformer]] coupled (economically feasible with such a small number of links), so the drive and controller do not require a common [[direct current|DC]] [[ground]], simplifying installation. Transformer coupling also eliminates unpredictable and unrepeatable "[[ground loop]]" problems, and provides for installation flexibility, since SDB drives can be physically added to or removed from a subsystem without disrupting its operation.<br />
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These four cables are emplaced in a single [[connector]] for actual installation of SDB units.<br />
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==Further reading==<br />
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* ''Digital Storage Technology Handbook'', 1989 (EC-H0374-45/89) - Chapter 4, The Digital Storage Interconnects<br />
* ''Digital Large System Mass Storage Handbook'', 1986 - Chapter 7, The Storage Interconnect<br />
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==External links==<br />
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[[Category: DEC Mass Storage]]</div>Jnc