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Acorn 32016 Second Processor

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Acorn 32016 Second Processor
32016 Second Processor, front view
Specifications
ManufacturerAcorn Computers (Acorn Scientific)
TypeTube second processor for the BBC Micro
Intro priceCambridge Co-Processor: £1,399 + VAT (512 KB), £1,699 (1 MB) in October 1985[1]
CPUNational Semiconductor NS32016 at 6 MHz
Memory256 KB (ANC05 leaflet); 512 KB or 1 MB (Cambridge Co-Processor)
Storage—
Display—
Sound—
ROM32 KB (two 128 Kbit EPROMs) holding the Pandora kernel
FPU / coprocessorNS32081
PowerInternal 15 W 5 V supply
Dimensions346 × 207 × 75 mm (maximum)
Weight2.1 kg
OS / FirmwarePanos
Model no.ANC05 (32016 Second Processor), ANC06 (Cambridge Co-Processor)

The Acorn 32016 Second Processor is an external Tube processor for the BBC Micro based on National Semiconductor's NS32016, with its own memory, ROM and mains power supply in the same "cheese wedge" case as the Acorn 6502 Second Processor. It runs Acorn's Panos operating system, loaded from disc by a ROM kernel called Pandora, and was sold with compilers for C, FORTRAN 77, Pascal and LISP as well as BBC BASIC.[2] Acorn later sold it through its scientific division as the Cambridge Co-Processor.[1]

The chip was announced as the 16032 and renamed 32016 before the product shipped, and some early BBC literature uses the old name.[3] Wikipedia records an earlier plan under the name Gluon.[4] Acorn User reported in September 1986 that Acorn had sold about 300 of the 32016 systems, 80 of them to Queen Mary College in London.[5]

Versions

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Versions
Name Code Memory Notes
32016 Second Processor ANC05 256 KB in Acorn's leaflet; Chris Whytehead's unit has 1 MB BBC Microcomputer System branding; his board is 0210,000 issue H with an NS32016D-8[2][3]
Cambridge Co-Processor ANC06 512 KB or 1 MB Acorn Scientific branding; his board is 0210,000 issue 2 with an NS32016D-6 and an empty FPU position[6]

The Acorn Cambridge Workstation uses a larger 32016 board with 4 MB, which does not fit the second processor case.[7]

Hardware

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Main board 0210,000: Tube connector and ULA at the left, CPU and support chips with gold labels, Pandora ROMs, and 32 RAM sockets along the bottom (photo: Chris Whytehead, CC BY-SA 3.0)

The single board fills the case behind the power supply. Two rows of RAM sockets run along one side and take either 64 Kbit or 256 Kbit DRAMs; Practical Computing reported that all production units used the 256 Kbit chips and that only 512 KB and 1 MB versions were to be sold, because the current software needed at least 512 KB.[1] The Tube interface is the same Ferranti ULA as on the 8-bit second processors. Pandora occupies two 27128 EPROMs, and the board has a space beside the processor for an NS32082 memory management unit, which was not fitted.[1] Acorn's leaflet lists the NS32081 floating point unit as standard;[2] Chris Whytehead's Cambridge Co-Processor has the FPU position empty.[6]

The NS32016 has 32-bit registers and a 16-bit external data bus, with a 24-bit address bus multiplexed with the data bus.[1]

Power supply

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Acorn's leaflet describes the supply as 15 W, 3 A at 5 V, with overvoltage and short circuit protection, and no fan. Input is 240 V 50 Hz through a moulded plug with a 3 A fuse.[2] The power cable, fuse holder and on/off switch are on the back panel.[3] Acorn's user guide puts the switch on the right of the rear panel, seen from the front.[8] No Acorn circuit diagram of the supply has been found online.

Warning: the supply inside the case runs from mains voltage. Unplug the unit before removing the lid.

Requirements and fitting

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  • A BBC Micro with OS 1.2 or later, the DNFS ROM in place of any separate DFS or NFS ROM, and on Winchester systems a special ADFS (ADFS/32) supplied with the co-processor. A Model B+ already has most of the ROMs it needs, plus ADFS for a Winchester.[8]
  • Disc drives: Panos needs dual 80-track double-sided drives (800 KB in total) or a Winchester or Econet file server.[8]
  • Because the Tube cable is short, the co-processor must stand immediately to the right of the BBC Micro. Plug the cable into the socket labelled Tube with the pin 1 triangle uppermost, in line with the triangle by the socket.[8]
  • Switch on the co-processor, then the BBC Micro. The usual start-up message is replaced by "Pandora 32016 version 1.00" and "Memory size 512 kilobytes" (or the size fitted), followed by the filing system and language.[8]

Fault finding

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Acorn's user guide lists five visible signs of a hardware fault: the start-up heading does not appear; the co-processor keeps switching itself off; floating point results are wrong; a floppy disc fails to copy; and the co-processor overheats. It tells owners to report them to the supplier.[8]

No service manual for the 0210,000 board has been found. Acorn's service manual for the Cambridge Workstation describes fault finding on that machine's 32016 board, which uses the same NS32000 chip set and Pandora firmware. Its general checks are a useful guide here, although its IC numbers belong to the ACW board:[7]

  1. Measure the 5 V supply at the board's Faston connectors. For the ACW board Acorn says it must be 5.00 V "and no less", and to adjust the supply if it is lower.
  2. Take care removing the NS32016 from its socket: the ceramic package cracks easily.
  3. Check the clocks. On the ACW board they come from the NS32201 timing and control unit (TCU pins 13, 11, 10 and 16).
  4. Check that the host reset (Tube ULA pin 20) and parasite reset (Tube ULA pin 37) go low while BREAK is held and rise when it is released.
  5. Look for address strobe pulses (ADS, TCU pin 6) about every four clock cycles, and program flow status pulses (PFS, CPU pin 39). A steady stream of PFS pulses means the processor is executing instructions.
  6. Once Pandora starts, its banner passes through the Tube, and there should be activity on the Tube chip select (Tube ULA pin 21) while it is sent.
  7. A faulty FPU either does not respond or, more rarely, gives wrong answers.[7]

The Tube ULA, ribbon cable and Tube connector checks on Acorn 6502 Second Processor#Fault finding apply to this unit as well, since the interface is the same.

Documentation

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  • Acorn 32016 Second Processor Documentation: the Cambridge Co-Processor User Guide (1985) and Acorn's leaflet APP 31.
  • Acorn Scientific's Panos and language manuals, including a provisional Panos Technical Reference Manual, are on Chris's Acorns.[3] Panos installation discs are on J. G. Harston's mdfs.net.[3]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 Cullis, Roger. "Cambridge 32016 Co-Processor: BBC mainframe add-on", Practical Computing, vol. 8 issue 10, October 1985. Scan via Chris's Acorns. Specification box (6 MHz, 512 KB or 1 MB, Panos 1.1, prices, volume shipment from October); 64K or 256K RAM chips, all production models with the larger chips; Ferranti Tube ULA; Pandora in two 27128 EPROMs; 32081 FPU; space for a 32082 MMU; separate power supply as on the 6502 and Z80 second processors.
  2. ↑ 2.0 2.1 2.2 2.3 Acorn Computers, leaflet "The British Broadcasting Corporation Microcomputer 32016 Second Processor", APP 31. Hosted on this wiki: File:Acorn 32016 Second Processor brochure (APP31).pdf. Technical data: ANC05, 256 KB of 32 × 64 Kbit 150 ns DRAM, 32 KB ROM in 2 × 128 Kbit, 6 MHz, four-layer PCB, 15 W 3 A 5 V two-rail power supply with overvoltage and short circuit protection, no fan, 240 V 50 Hz, 3 A plug fuse, 346 × 207 × 75 mm maximum, 2.1 kg; BBC Micro Model B with MOS 1.2 or later required; FPU as standard.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Whytehead, Chris. "Acorn ANC05 32016 2nd processor", Chris's Acorns, The Centre for Computing History (retrieved 2026-10-01). NS32016D-8 CPU at 6 MHz, 1 MB of TMS4256 in 32 sockets, Ferranti Tube ULA, Pandora ROMs 0201-263-02 and 0201-264-02, board 0210,000 issue H, serial R&D ANC05 130; power supply at the front of the case.
  4. ↑ "BBC Micro expansion unit", Wikipedia (retrieved 2026-10-01), section "32016 second processor": the Gluon plan, branding as "Acorn Cambridge Co-Processor" and as "BBC Microcomputer System 32016 Second Processor", 256 KB then 512 KB or 1 MB, the 1 MB model at £1,295 including VAT.
  5. ↑ Yoke, Peter. "Acorn's Supercomputer", Acorn User, September 1986, pp. 145 to 147. Scan via Chris's Acorns. About 300 machines sold, 80 at Queen Mary College; 1 MB units typically £1,400; network crashes with early Panos, improved with Panos 1.3.
  6. ↑ 6.0 6.1 Whytehead, Chris. "Acorn ANC06 Cambridge Co-Processor", Chris's Acorns (retrieved 2026-10-01). NS32016D-6 at 6 MHz, 1 MB of TMM41256P, space for the FPU but none fitted, Pandora ROMs 0201-263-02 and 0201-264-02, board "32016 Second processor" 0210,000 issue 2, serial 23-ANC06-0001493; "only very minor differences" from the 32016 2nd processor.
  7. ↑ 7.0 7.1 7.2 Acorn Computers, ACW 443 Service Manual, reference 0420,001, issue 1, January 1987. PDF via Chris's Acorns. Section 1.3.1 (4 MB 32016 card, NS32016 CPU, NS32081 FPU, 32201 TCU) and section 5.7, fault finding on the 32016 processor PCB.
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Acorn Scientific, Cambridge Co-Processor User Guide, issue 1, July 1985. Hosted on this wiki: Acorn 32016 Second Processor Documentation. Capabilities p. 5; ROMs needed p. 6; ROMs for the B+ p. 6; connecting p. 7; starting up p. 9; Panos needs dual 80-track drives p. 11; trouble-shooting p. 51.


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