Difference between revisions of "BM873 ROM"
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| − | + | [[Image:BM873.jpg|250px|right|thumb|A BM783 card, showing the connector to the [[front panel]] cable, and diode array]] | |
| − | The | + | The '''BM873 ROM''' card was a [[UNIBUS]] [[Read-only memory|ROM]] card for the [[PDP-11]] series of computers; it was a [[DEC card form factor|quad]] format card, and contained 256 [[word]]s of memory (optionally limited to 128 words), contained in four [[PROM]] [[integrated circuit|chips]] (two, when the limitation option was selected). |
| − | In addition, an edge connector provided four external input lines, each of which (when | + | The board appeared at [[address]]es from 773000 to 773776; if the 128-word limitation is enabled, the top address is 773376. Several of the computers it was intended for use with ([[PDP-11/40]], [[PDP-11/45]]) could be configured so that the host computer jumped to the code on the board on power-on. |
| + | |||
| + | In addition, an edge connector provided four external input lines, each of which (when pulled low) forced the computer to jump to a particular address (configured by a group of 8 [[diode]]s, four groups in total - one for each input line) within the card's address space. This was done via a simulated power-fail restart, and then forcing the first two read cycles on the UNIBUS after the power-up to read data specially provided by the board. | ||
==Jumpers== | ==Jumpers== | ||
| − | Jumpers W1 and W2 adapt the board to variations in fetching the new PS/PC after power-up - the bus cycles which the board interferes with, to force the new PC to go to a specific location within the board. Some machines, like the -11/40, fetch the PS before the PC; others, like -11/45, fetch the PC first. | + | Jumpers W1 and W2 adapt the board to variations in fetching the new [[Processor Status Word|PS]]/[[Program Counter|PC]] after power-up - the bus cycles which the board interferes with, to force the new PC to go to a specific location within the board. Some machines, like the -11/40, fetch the PS before the PC; others, like -11/45, fetch the PC first. |
Jumper W3, when installed, limits the card to 128 words. | Jumper W3, when installed, limits the card to 128 words. | ||
| − | Resistor R3 can be removed to disable the 'default address' feature. This is that on a system configured to fetch the new PS/PC from ROM on power-on - a capability which exists in the -11/40 and -11/45, when used with MOS memory - on a power-on, with no external line asserted, the board acted as if the first external input had been asserted. | + | Resistor R3 can be removed to disable the 'default address' feature. This is that on a system configured to fetch the new PS/PC from ROM on power-on - a capability which exists in the -11/40 and -11/45, when used with MOS memory - on a power-on, with no external line asserted, with this resistor in place, the board acted as if the first external input had been asserted. |
==Versions== | ==Versions== | ||
| − | Most versions were used for [[ | + | Most versions were used for [[bootstrap]]ping the machine, from [[disk]], [[paper tape|paper]] and [[magnetic tape]], etc, but it could be used for any purpose. |
| − | In addition to an un-programmed variant, which the user could program as they wanted, the board came from DEC in several pre-programmed variants, designated | + | In addition to an un-programmed variant, which the user could program as they wanted, the board came from DEC in several pre-programmed variants, designated BM783-Yx (where 'x' is a capital letter, starting with 'A'), set up to perform various functions. Many of the later variants were used to boot the PDP-11/40 used as the [[front end]] processor in the [[KL10]]. |
===Variants=== | ===Variants=== | ||
| − | * BM873-YA - Boot from disks ([[RF11]], [[RK11]], [[RP11]], [[RC11]]), [[TC11]] [[DECtape]], [[TM11]] magnetic tape, [[TA11]] casette magnetic tape, | + | * BM873-YA - Boot from disks ([[RF11 disk controller|RF11]], [[RK11 disk controller|RK11]], [[RP11 disk controller|RP11]], [[RC11 disk controller|RC11]]), [[TC11 DECtape controller|TC11]] [[DECtape]], [[TM11 magtape controller|TM11]] [[magnetic tape]], [[TA11 Magnetic Tape Cassette controller|TA11]] casette magnetic tape, [[PC04/PC05 High-Speed Paper-Tape Reader/Punch|PC05]] high-speed [[paper tape]] reader, and [[asynchronous serial line]] |
| − | * BM873-YB - As above, with the addition of RS0x and RP0x | + | * BM873-YB - As above, with the addition of [[RS03/04 disk drive|RS0x]] and [[RP04 disk drive|RP0x]] [[disk]]s and [[TU16 magtape drive|TU16]] tapes; in addition, booting from units other than 0 (with the unit being specified in the console switch register) |
| − | * BM873-YC - As the -YA variant, with added support for the [[DU11]] synchronous line interface | + | * BM873-YC - As the -YA variant, with added support for the [[DU11 synchronous serial line interface|DU11]] synchronous line interface |
| − | * BM873-YD - 1080 | + | * BM873-YD - [[KL10]] 1080 front end; supported booting from, and dumping to, TC11, RP0x, and [[DTE20 Ten-Eleven Interface]] |
* BM873-YE - Unknown | * BM873-YE - Unknown | ||
| − | * BM873-YF - 2040 console; same capabilities as -YD, except the [[RX11]] replaced the TC11 | + | * BM873-YF - KL10 2040 console; same capabilities as -YD, except the [[RX11 floppy disk controller|RX11]] replaced the TC11 |
| − | * BM873-YG - DN87 communications; supported booting from a [[DL11]] and the DTE20, and dumping to the latter | + | * BM873-YG - DN87 communications; supported booting from a [[DL11 asynchronous serial line interface|DL11]] and the DTE20, and dumping to the latter |
| − | * BM873-YH - 10xx/20xx console; supported booting from TC11, RX11, RP0x, and possibly the DTE20 10/11 interface (the | + | * BM873-YH - 10xx/20xx console; supported booting from TC11, RX11, RP0x, and possibly the DTE20 10/11 interface (the documentation is contradictory) |
* BM873-YJ - 10xx/20xx console/communications; supported booting from TC11, RX11, RP0x, DL11 and the DTE20, and dumping to the latter | * BM873-YJ - 10xx/20xx console/communications; supported booting from TC11, RX11, RP0x, DL11 and the DTE20, and dumping to the latter | ||
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* [[UNIBUS boot ROMs]] | * [[UNIBUS boot ROMs]] | ||
| + | |||
| + | ==External links== | ||
| + | |||
| + | * [http://www.bitsavers.org/pdf/dec/unibus/DEC-11-H873A-B-D_BM873_Restart_Loader_Apr74.pdf BM873 restart/loader] (DEC-11-H873A-B-D) | ||
| + | * [http://shop-pdp.net/~stuff/PDFs/DEC/DEC_BM873_Restart_Loader_RevA_Feb74.pdf BM873 Restart Loader engineering drawings] | ||
| + | * [http://pdp-10.trailing-edge.com/BB-H311C-RM/01/swskit-documentation/kl873.mem.html KL873.MEM] - ''KL10 BM873 Bootstrap ROMs'' | ||
| + | * [http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/ROMs/M873-YA.mac M873-YA.mac] - Dis-assembled and commented dump of BM873-YA boot ROMs | ||
==Reference== | ==Reference== | ||
* EK-BM873-TM-004, ''BM873 restart/loader'' | * EK-BM873-TM-004, ''BM873 restart/loader'' | ||
| − | + | ||
| + | [[Category: UNIBUS ROMs]] | ||
Latest revision as of 00:02, 20 November 2021
A BM783 card, showing the connector to the front panel cable, and diode array
The BM873 ROM card was a UNIBUS ROM card for the PDP-11 series of computers; it was a quad format card, and contained 256 words of memory (optionally limited to 128 words), contained in four PROM chips (two, when the limitation option was selected).
The board appeared at addresses from 773000 to 773776; if the 128-word limitation is enabled, the top address is 773376. Several of the computers it was intended for use with (PDP-11/40, PDP-11/45) could be configured so that the host computer jumped to the code on the board on power-on.
In addition, an edge connector provided four external input lines, each of which (when pulled low) forced the computer to jump to a particular address (configured by a group of 8 diodes, four groups in total - one for each input line) within the card's address space. This was done via a simulated power-fail restart, and then forcing the first two read cycles on the UNIBUS after the power-up to read data specially provided by the board.
Jumpers
Jumpers W1 and W2 adapt the board to variations in fetching the new PS/PC after power-up - the bus cycles which the board interferes with, to force the new PC to go to a specific location within the board. Some machines, like the -11/40, fetch the PS before the PC; others, like -11/45, fetch the PC first.
Jumper W3, when installed, limits the card to 128 words.
Resistor R3 can be removed to disable the 'default address' feature. This is that on a system configured to fetch the new PS/PC from ROM on power-on - a capability which exists in the -11/40 and -11/45, when used with MOS memory - on a power-on, with no external line asserted, with this resistor in place, the board acted as if the first external input had been asserted.
Versions
Most versions were used for bootstrapping the machine, from disk, paper and magnetic tape, etc, but it could be used for any purpose.
In addition to an un-programmed variant, which the user could program as they wanted, the board came from DEC in several pre-programmed variants, designated BM783-Yx (where 'x' is a capital letter, starting with 'A'), set up to perform various functions. Many of the later variants were used to boot the PDP-11/40 used as the front end processor in the KL10.
Variants
- BM873-YA - Boot from disks (RF11, RK11, RP11, RC11), TC11 DECtape, TM11 magnetic tape, TA11 casette magnetic tape, PC05 high-speed paper tape reader, and asynchronous serial line
- BM873-YB - As above, with the addition of RS0x and RP0x disks and TU16 tapes; in addition, booting from units other than 0 (with the unit being specified in the console switch register)
- BM873-YC - As the -YA variant, with added support for the DU11 synchronous line interface
- BM873-YD - KL10 1080 front end; supported booting from, and dumping to, TC11, RP0x, and DTE20 Ten-Eleven Interface
- BM873-YE - Unknown
- BM873-YF - KL10 2040 console; same capabilities as -YD, except the RX11 replaced the TC11
- BM873-YG - DN87 communications; supported booting from a DL11 and the DTE20, and dumping to the latter
- BM873-YH - 10xx/20xx console; supported booting from TC11, RX11, RP0x, and possibly the DTE20 10/11 interface (the documentation is contradictory)
- BM873-YJ - 10xx/20xx console/communications; supported booting from TC11, RX11, RP0x, DL11 and the DTE20, and dumping to the latter
See also
External links
- BM873 restart/loader (DEC-11-H873A-B-D)
- BM873 Restart Loader engineering drawings
- KL873.MEM - KL10 BM873 Bootstrap ROMs
- M873-YA.mac - Dis-assembled and commented dump of BM873-YA boot ROMs
Reference
- EK-BM873-TM-004, BM873 restart/loader
