Difference between revisions of "Synchronous Backplane Interconnect"
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| − | The '''Synchronous Backplane Interconnect''' (sometimes given as the acronym, '''SBI''') was the high-speed bus which connected the major functional units ([[Central Processing Unit|CPU]], [[main memory]], [[Input/output|I/O]] adapters, etc), in early [[VAX]] | + | The '''Synchronous Backplane Interconnect''' (sometimes given as the acronym, '''SBI''') was the high-speed [[bus]] which connected the major functional units ([[Central Processing Unit|CPU]], [[main memory]], [[Input/output|I/O]] adapters, etc), in early [[VAX]] systems: |
| + | |||
| + | * [[VAX-11/780]] | ||
| + | * [[VAX-11/782]] | ||
| + | * [[VAX-11/785]] | ||
| + | |||
| + | It was later used as an I/O bus in the [[VAX 8600 series]]: | ||
| + | |||
| + | * [[VAX 8600]] | ||
| + | * [[VAX 8650]] | ||
| + | |||
| + | ==Technical details== | ||
It was synchronous, in that everything on the bus happened in fixed time slots; but it was somewhat asynchronous, in that the slots which were part of an operation (e.g. requesting a read; and the data being returned) had no fixed temporal relationship. The slots of different operations may be interleaved; e.g. after a memory read is started in one slot, some other operation might use some of the slots before the one in which the data is returned. | It was synchronous, in that everything on the bus happened in fixed time slots; but it was somewhat asynchronous, in that the slots which were part of an operation (e.g. requesting a read; and the data being returned) had no fixed temporal relationship. The slots of different operations may be interleaved; e.g. after a memory read is started in one slot, some other operation might use some of the slots before the one in which the data is returned. | ||
| − | Allocation of slots was done by a fully-distributed arbitration process, among all the functional units attached to the SBI (called 'nexi'). The arbitration is overlaid, temporally, with operation: the selection of which nexus will perform an operation in a following slot is done during the previous slot; during that previous slot, some other operation may have happened. A nexus can be classified as being one of: | + | Allocation of time slots was done by a fully-distributed arbitration process, among all the functional units attached to the SBI (called 'nexi'). The arbitration is overlaid, temporally, with operation: the selection of which nexus will perform an operation in a following slot is done during the previous slot; during that previous slot, some other operation may have happened. A nexus can be classified as being one of: |
* Commander - a nexus that transmits an [[address]] and command | * Commander - a nexus that transmits an [[address]] and command | ||
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In addition to data transfer operations, [[interrupt]] operations are also supported. | In addition to data transfer operations, [[interrupt]] operations are also supported. | ||
| − | [[Category: | + | ==Units== |
| − | [[Category: | + | |
| + | The following bus adapters: | ||
| + | |||
| + | * [[DW780 Unibus Adapter]] | ||
| + | * [[RH780 Massbus Adapter]] | ||
| + | |||
| + | and devices: | ||
| + | |||
| + | * [[CI780 Computer Interconnect Adapter]] | ||
| + | * [[DR780 High-Performance Channel Interface]] | ||
| + | |||
| + | may be connected to the SBI. | ||
| + | |||
| + | ==External links== | ||
| + | |||
| + | * [http://www.bitsavers.org/pdf/dec/vax/780/EK-11780-UG-001_VAX-11_780_Hardware_Users_Guide_197902.pdf VAX-11/780 Hardware User's Guide] (EK-11780-UG-001) - the SBI is covered in Section 1.3.2.1, pp. 21-22 of the PDF | ||
| + | * [http://www.bitsavers.org/pdf/dec/vax/780/EK-MM780-TD-001_Translation_Buffer_and_Cache_and_SBI_Control_Technical_Description_197804.pdf Translation Buffer, Cache and SBI Control Technical Description] (EK-MM780-TD-001) - the SBI is covered in Section 1.8.1, pp. 29-31 of the PDF, and Section 2.3, pp. 72-129 | ||
| + | * [http://www.bitsavers.org/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_1_1986.pdf VAX Hardware Handbook Volume 1] - the SBI is covered in detail in Chapter 9 (pp. 321-344 of the PDF) | ||
| + | |||
| + | [[Category: VAX Buses]] | ||
| + | [[Category: SBI]] | ||
Latest revision as of 16:09, 14 May 2024
The Synchronous Backplane Interconnect (sometimes given as the acronym, SBI) was the high-speed bus which connected the major functional units (CPU, main memory, I/O adapters, etc), in early VAX systems:
It was later used as an I/O bus in the VAX 8600 series:
Technical details
It was synchronous, in that everything on the bus happened in fixed time slots; but it was somewhat asynchronous, in that the slots which were part of an operation (e.g. requesting a read; and the data being returned) had no fixed temporal relationship. The slots of different operations may be interleaved; e.g. after a memory read is started in one slot, some other operation might use some of the slots before the one in which the data is returned.
Allocation of time slots was done by a fully-distributed arbitration process, among all the functional units attached to the SBI (called 'nexi'). The arbitration is overlaid, temporally, with operation: the selection of which nexus will perform an operation in a following slot is done during the previous slot; during that previous slot, some other operation may have happened. A nexus can be classified as being one of:
- Commander - a nexus that transmits an address and command
- Responder - a nexus that recognizes an address and responds to the accompanying command
- Transmitter - a nexus that drives the SBI lines
- Receiver - a nexus that examines the SBI lines
Obviously, a nexus may appear in different categories over time; e.g. a CPU is a transmitter during a write to memory, and a receiver during a red.
The SBI has 32 data lines, and 28 address lines (addresses name long-words). It can transfer units of 8, 16, 32 ('long-word'), and 64 ('quad-word') bits. Data is protected by parity on the SBI.
In addition to data transfer operations, interrupt operations are also supported.
Units
The following bus adapters:
and devices:
may be connected to the SBI.
External links
- VAX-11/780 Hardware User's Guide (EK-11780-UG-001) - the SBI is covered in Section 1.3.2.1, pp. 21-22 of the PDF
- Translation Buffer, Cache and SBI Control Technical Description (EK-MM780-TD-001) - the SBI is covered in Section 1.8.1, pp. 29-31 of the PDF, and Section 2.3, pp. 72-129
- VAX Hardware Handbook Volume 1 - the SBI is covered in detail in Chapter 9 (pp. 321-344 of the PDF)
