VAX 11: Семейство супермини-компьютеров Digital

Family of superminicomputers by Digital

The VAX 11 is a discontinued family of 32 bit superminicomputers, running the Virtual Address eXtension (VAX) instruction set architecture (ISA), developed and manufactured by Digital Equipment Corporation (DEC). Development began in 1976. In addition to being powerful machines in their own right, they also offer the additional ability to run user mode PDP 11 code (thus the 11 in VAX 11), offering an upward compatible path for existing customers. The first machine in the series, the VAX 11/780, was announced in October 1977. Its former competitors in the minicomputer space, like Data General and Hewlett Packard, were unable to successfully respond to the introduction and rapid update of the VAX design. DEC followed the VAX 11/780 with the lower cost 11/750, and the even lower cost 11/730 and 11/725 models in 1982. More powerful models, initially known as the VAX 11/790 and VAX 11/795, were instead rebranded as the VAX 8600 series. The VAX 11 line was discontinued in 1988, having been supplanted by the MicroVAX family on the low end, and the VAX 8000 family on the high end.

VAX 11 registers 31 23 15 07 06 05 04 03 02 01 00 (bit position) General registers R0 Register 0 R1 Register 1 R2 Register 2 R3 Register 3 R4 Register 4 R5 Register 5 R6 Register 6 R7 Register 7 R8 Register 8 R9 Register 9 R10 Register 10 R11 Register 11 Index registers R12 / AP Register 12 / Argument Pointer R13 / FP Register 13 / Frame Pointer R14 / SP Register 14 / Stack Pointer Program counter R15 / PC Register 15 / Program Counter Status flags   I V N Z C Processor Status Word     Floating Point Status Register

The VAX 11/780, code named "Star", was introduced on 25 October 1977 at DEC's Annual Meeting of Shareholders. It is the first computer to implement the VAX architecture. The KA780 central processing unit (CPU) is built from Schottky transistor transistor logic (TTL) devices and has a 200 ns cycle time (5 MHz) and a 2 KB cache. Memory and I/O are accessed via the Synchronous Backplane Interconnect (SBI). The CPU is microprogrammed. The microcode is loaded at boot time from an 8" floppy disk controlled by a front end processor, a PDP 11/03, which is used to run local and remote diagnostics. The VAX 11/780 originally supported up to 8MB of memory through one or two MS780 C memory controllers, with each controller supporting between 128KB 4MB of memory. The later MS780 E memory controller supports 4MB 64MB of memory, allowing the VAX 11/780 to support up to a total of 128MB of memory. The KA780 has a 29 bit physical address space, allowing it to address a theoretical maximum of 512MB of memory. The memory is constructed from 4 or 16 kbit metal oxide semiconductor (MOS) RAM chips mounted on memory array cards. Each memory controller controls up to 16 array cards. The memory is protected by error correcting code (ECC). The VAX 11/780 uses the Unibus and Massbus for I/O. Unibus is used for attaching lower speed peripherals such as terminals and printers and Massbus for higher speed disk and tape drives. After the introduction of the RA series drives in December 1982 the Unibus was also used for high speed peripherals. Both buses are provided by adapters that interface the bus to the SBI. All systems come with one Unibus as standard, with up to four supported. Massbus is optional, with up to four supported. The VAX 11/780 also supports Computer Interconnect (CI), a proprietary network to attach disk drives and potentially share them with other VAX computers. This feature can connect VAX computers in a VMScluster. Digital used the performance of the VAX 11/780 as a reference point for describing the performance of subsequent VAX models. The performance of the VAX 11/780 became known as 1 VAX Unit of Performance (or 1.0 VUPs). Other VAX models are rated as a multiple of the VAX 11/780's performance, for example, a 2.0 VUPs VAX is twice as fast as the VAX 11/780.

The VAX 11/782, code named "Atlas", is a dual processor VAX 11/780 introduced in 1982. Both processors share the same MA780 multiport memory bus and the system operates asymmetrically, with the primary CPU performing all I/O operations and process scheduling with the second, attached processor only used for additional computationally intensive work. For multistream computation intensive tasks the system delivers up to 1.8 times the performance of a VAX 11/780.

The VAX 11/785, code named "Superstar", was introduced in April 1984. Its KA785 CPU is essentially a faster KA780, with a CPU cycle time of 133 ns (7.52 MHz) versus the 200 ns (5 MHz) CPU cycle time of the KA780, giving a performance of 1.5 VUPs. The decrease in CPU cycle time is accomplished through use of Fairchild Advanced Schottky TTL (FAST) logic. The use of gate arrays decreases power consumption, and increases reliability compared with the VAX 11/780. The KA750 CPU has a 320 ns cycle time (3.125 MHz), and a VUPs rating of 0.6. While the 11/780 boots from a 8” floppy via its console processor, the VAX 11/750 is equipped with a TU58 (DECtape II) cassette drive for first level booting and diagnostics.

A ruggedized rack mount VAX 11/750.

Introduced in April 1982, the VAX 11/730, code named "Nebula", is a still more compact, still lower performance bit slice implementation of the VAX architecture using AMD Am2900 chips for the CPU. The KA730 CPU has a 270 ns cycle time (3.70 MHz), and a VUPs rating of 0.3.

Code named "LCN" ("Low Cost Nebula"), it is a cost reduced model of the VAX 11/730. It uses the same KA730 CPU as the VAX 11/730, but is housed in a more compact enclosure designed to reduce noise and heat ("55 dB" and "575 W (max. )"), making it more suitable for use in an office environment. It supports up to 3MB of memory.

The VAX 11/790 and VAX 11/795 are the original names for the VAX 8600 and VAX 8650 respectively.

The Living Computer Museum of Seattle, Washington maintains a VAX 11/780 5 (field upgraded VAX 11/780) running OpenVMS 7.3. The Computer History Museum of Mountain View, California has three VAX 11/780 systems, one VAX 11/725, one VAX 11/730, and one VAX 11/750 within its permanent collection. The RECHENWERK Computer & Technikmuseum Halle in Halle, Germany holds a VAX 11/730 and a very rare East German clone of a VAX 11/780 named Robotron K 1840 in its permanent exhibition. The Verde Binario retrocomputing association has a VAX 11/780 to which they dedicated a calendar. The Large Scale Systems Museum in New Kensington, PA has VAX 11/785, VAX 11/780, VAX 11/750, and VAX 11/730 systems. The Luddy School of Informatics, Computing, and Engineering at IU Bloomington in Indiana has on display a VAX 11/780, as well as various other computers from the time.