Difference between revisions of "FPJ11 floating point accelerator"
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Although the DCJ11 contains a full implementation of the FP11 floating point [[instruction]]s, in [[microcode]], if a J-11 CPU board has an FPJ11 installed, the DCJ111 will automatically notice the presence of the FPJ11, and allow it to handle all floating-point instructions. | Although the DCJ11 contains a full implementation of the FP11 floating point [[instruction]]s, in [[microcode]], if a J-11 CPU board has an FPJ11 installed, the DCJ111 will automatically notice the presence of the FPJ11, and allow it to handle all floating-point instructions. | ||
| − | Addition of the FPJ11 improves floating-point | + | Addition of the FPJ11 improves floating-point performance by a factor of 5 to 8. The interface between the DCJ11 and the FPJ11 is designed to allow overlap between execution of floating point instructions in the FPJ11, and execution of non-floating point instructions in the DCJ11. |
==Versions== | ==Versions== | ||
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* μNote #025, "FPJ11-AA Compatibility with the LSI-11/73 (KDJ11-A)", 28 April 1985 | * μNote #025, "FPJ11-AA Compatibility with the LSI-11/73 (KDJ11-A)", 28 April 1985 | ||
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[[Category: PDP-11 Processors]] | [[Category: PDP-11 Processors]] | ||
Latest revision as of 20:06, 2 July 2023
The FPJ11 floating point accelerator is an optional floating point co-processor for the DCJ11 J-11 PDP-11 CPU chip, which implements the full FP11 floating point instruction set. The FPJ11 is a single chip which is plugged into a socket on a KDJ11 CPU card.
Although the DCJ11 contains a full implementation of the FP11 floating point instructions, in microcode, if a J-11 CPU board has an FPJ11 installed, the DCJ111 will automatically notice the presence of the FPJ11, and allow it to handle all floating-point instructions.
Addition of the FPJ11 improves floating-point performance by a factor of 5 to 8. The interface between the DCJ11 and the FPJ11 is designed to allow overlap between execution of floating point instructions in the FPJ11, and execution of non-floating point instructions in the DCJ11.
Versions
Two versions of the FPJ11 exist; the FPJ11-AA and the FPJ11-AB. DEC had a number of problems with 'corner cases' (e.g. DMA during certain floating point instructions), and had to issue revised versions of the FPJ11 and some J-11 CPU boards (e.g. the KDJ11-A) to fix them all.
External links
- DEC Semiconductor Databook, Volume 1, pp. 335-359
- FPJ11 Theory of Operation μNote #040, 17 September 1985
- DCJ11/FPJ11 Compatibility
Further reading
- μNote #025, "FPJ11-AA Compatibility with the LSI-11/73 (KDJ11-A)", 28 April 1985
