KL10

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KL10
Manufacturer: Digital Equipment Corporation
Architecture: PDP-10
Year Design Started: January, 1972
Year First Shipped: June, 1975
Form Factor: mainframe
Word Size: 36 bits
Logic Type: ECL ICs
Design Type: clocked synchronous, microcoded
Microword Width: 80
Microcode Length: 1280 (Model A)
2K (Model B)
Clock Speed: 500 nsec
Cache Size: 2K words
Memory Speed: 1.0 μsec (initial core memory), 500 nsec (later MOS main memory)
Physical Address Size: 22 bits
Virtual Address Size: 18 bits (Model A and B)
23 bits (Model E)
Memory Management: paging, 512-word pages
Operating System: TOPS-10, TOPS-20, ITS, WAITS, TENEX, TYMCOM-X
Predecessor(s): KI10
Successor(s): none
Price: US$250K (CPU), US$600K-1.2M (system)


The KL10 was the third generation of PDP-10 processors. It was built out of ECL, on hex cards. It was the first microprogrammed PDP-10 processor; the design was inspired by Stanford's Superfoonly.

The CPU had two main units, the 'E Box' ('Execution') and the 'M Box' ('Memory'). It provided three types of busses to the rest of the components of the system; the 'E Bus', from the E Box; and the 'S Bus' ('Storage'), and later the 'C Bus' ('Channel'), from the M Box. The S Bus was for the attachment of main memory units, while the C Bus alowed DMA accesss to main memory.

There were a number of variants over the lifetime of the KL10; the most significant division being between systems with an external memory bus(compatible with the earlier KA10 and KI10), and those with an internal memory bus (the native S Bus).

The former included a DMA20 Memory Bus Controller, attached to the S Bus, to provide the external memory bus. Similarly, a DIA20 In/Out Bus Contoller, attached to the E Bus, provided a KA10/KI10 compatible I/O bus.

The later so-called 'Model B' KL10 supportedd up to 4 DTE20 Interfaces (which allowed connection of a PDP-11 front end) and up to 8 RH20 MASSBUS controllers could be connected to the E Bus (the latter also connected to the C Bus). At least one PDP-11, the 'master', was required; it could bootstrap the KL10, including loading the microcode. (The earlier 'Model A' only supported a single DTE20, and no RH20s.)

The KL10 was used in the DECsystem-10 models 1080 and 1090 systems (with an external memory bus), and in the larger DECSYSTEM-20 20xx systems (with an internal memory bus).

Later Model B KL10's (sometimes denoted as the 'KL10-PV') supported the 'Extended' PDP-10 architecture, with support for multiple 'sections' (256K-word address spaces), available to both the kernel and the user (although apparently only TOPS-20 supported the latter).

Like its predecessor, the KI10, it was initially released in a single-processor version; a two-CPU version was released later.

Well-known KL10's

There was a single KL10 ITS machine, MIT-MC. It was later renamed to MX and was shut down in 1988. It is now in storage at the Living Computers Museum. There was also a KL10 in the Stanford WAITS system.

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