KS10

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KS10
Manufacturer: Digital Equipment Corporation
Architecture: PDP-10
Year Introduced: 1978
Form Factor: small mainframe
Word Size: 36 bits
Logic Type: LS TTL ICs
Design Type: clocked synchronous microcoded
Microword Width: 96
Microcode Length: 2K
Clock Speed: 300 nsec (micro-cycle)
Cache Size: 512 words
Cache Speed: 300 nsec
Memory Speed: 0.9 μsec
Physical Address Size: 19 bits (some had 20)
Virtual Address Size: 18 bits
Memory Management: paging, 512-word pages
Operating System: TOPS-10, TOPS-20, ITS
Predecessor(s): KL10
Successor(s): None


The KS10 was the fourth and last generation of PDP-10 processors (themselves, exact re-implementations of the earlier PDP-6 architecture). It was intended as a small, low-cost entry model, not as a replacement for the earlier KL10 mainframe.

8 different sets of CPU registers were provided, to speed up interrupt handling. The main memory used ECC for error detection (and possibly correction).

For I/O, it used a pair of UNIBUSes, driven by adapters which interfaced them to the KS10's internal bus. One was for the disks only, the other for all other devices (magnetic tape, asynchronous serial lines, etc). A separate page table mapped the UNIBUS address space into the KS10's main memory for DMA operations.

The UNIBUS which is used for the disks was run in 18-bit mode (the two parity lines on that UNIBUS were recycled into two extra data lines). That UNIBUS had only an RH11, mounted in the main CPU cabinet to drive the MASSBUS to the disks. (Only MASSBUS disks were supported, since an 18-bit data path was needed).

Internal details

It was built out of LS TTL chips, along with AMD 2901 4-bit-wide bit slice chips. The CPU was on four super hex cards:

  • DPE data path
  • DPM data path
  • CRA control store
  • CRM control store

Additional super hex cards held:

  • CSL - the console (driven by an Intel 8080A), and bus arbitrator
  • MMC - main memory controller
  • MMA - DRAM memory array modules (2 to 8)
  • UBA - UNIBUS adapters (2, optionally 3)