Commit | Line | Data |
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f6e94cb2 AT |
1 | # Overview # |
2 | ||
3 | I've started using my PDP-11 for instrument control and wanted faster floating | |
4 | point (FP) calculations. My PDP-11/83 is based on the DCJ11 chipset which | |
5 | provides a microcoded implementation of the PDP-11 FP instructions. However, | |
6 | there was a hardware FP co-processor, the FPJ11, that was designed to work with | |
7 | the DCJ11 and provides a 5x-8x speedup on FP operations. Unfortunately, the | |
8 | documentation contains a few references that made me hesitant to simply | |
9 | purchase an FPJ11 and plug it in. | |
10 | ||
11 | For example, DEC Micronote #25 mentions that | |
12 | ||
13 | An FPJ11-AA installed on a KDJ11-AA may APPEAR to work | |
14 | but cache errors and parity errors may occur. | |
15 | ||
16 | Yikes! | |
17 | ||
18 | What follows is the compatibility information necessary to add an FPJ11 to a | |
19 | DCJ11-based PDP-11. It has been condensed from various USENET postings and DEC | |
20 | manuals. | |
21 | ||
22 | # DJC11/FPJ11 Compatibility # | |
23 | ||
24 | Commercially released DCJ11 chipsets ran at either 15 or 18 MHz and there were | |
25 | two versions of the FPJ11 to match. The part number is written on the gold | |
26 | cover in the middle of the ceramic package. If you have an 18 MHz DCJ11 but can | |
27 | only find a 15 MHz FPJ11 it is possible to change the crystal on the CPU board | |
28 | to 15 Mhz. This would require an extremely FP-heavy workload to be worthwhile. | |
29 | ||
30 | | FPJ11 | Speed | | |
31 | | ----------- | ------ | | |
32 | | 21-21858-05 | 15 MHz | | |
33 | | 21-21858-06 | 18 MHz | | |
34 | ||
35 | In addition to clock speed, the earliest DCJ11s must be avoided as they are | |
36 | simply incompatible. This part number is located on the white ceramic package, | |
37 | between the DC334 Data chip and DC335 Control chip. | |
38 | ||
39 | | DCJ11 | Speed | FPA Compat? | | |
40 | | ----------- | ------ | ----------- | | |
41 | | 57-19400-04 | 15 MHz | No | | |
42 | | 57-19400-08 | 15 MHz | Yes | | |
43 | | 57-19400-09 | 18 MHz | Yes | | |
44 | ||
45 | ||
46 | # KDJ11 CPU Board Compatibility # | |
47 | ||
48 | ||
49 | Excluding the PDP-11/53 CPU boards that lack a socket for the FPJ11 and the | |
50 | PDP-11/93 CPU board that always includes the FPJ11 leaves us with the following | |
51 | set of CPU boards from the PDP-11/73 and /83 that are potential FPJ11 | |
52 | recipients. | |
53 | ||
54 | | KDJ11-xx | M819x-xx | FPA Compat? | Notes | | |
55 | | -------- | -------- | ----------- | ------------------------------------------------------------------------------------------ | | |
56 | | KDJ11-AA | M8192 | No | DEC uNOTE #25 states this board was upgradeable. Some FPJ11-compatible versions may exist. | | |
57 | | KDJ11-AB | M8192-YB | Yes | When the FPJ11 is installed this board magically becomes an M8192-YC/KDJ11-AC. | | |
58 | | KDJ11-BC | M8190 | No | | | |
59 | | KDJ11-BB | M8190-AB | Yes | When the FPJ11 is installed this board magically becomes an M8190-AC/KDJ11-BD. | | |
60 | | KDJ11-BA | M8190-AD | Yes | When the FPJ11 is installed this board magically becomes an M8190-AE/KDJ11-BF. | | |
61 | ||
62 | # FPJ11 Testing # | |
63 | ||
64 | When the KDJ11-B detects an installed FPJ11 it flags bit 8 (counting from 0) in | |
65 | the Maintenance Register located at `17 777 750`. Using ODT to test on a | |
66 | freshly powered up Qbus system with FPJ11 installed: | |
67 | ||
68 | @17777750/000445 | |
69 | ||
70 | And on the same system with the FPJ11 removed: | |
71 | ||
72 | @17777750/000045 | |
73 | ||
74 | Note that your results may be different since this register also encodes | |
75 | Unibus/Qbus, KDJ11 module type, BPOK status, power up mode, and halt/trap | |
76 | options. Exact details can be found in the KDJ11-B CPU Module User's Guide | |
77 | (EK-KDJ1B-UG-001) starting on page 1-43. |