SCSI Emulation Of A Rare Peripheral For The Acorn BBC Micro

Mass storage presents a problem for those involved in the preservation of older computer hardware. While today’s storage devices are cheap and huge by the standards of decades ago their modern interfaces are beyond the ability of most older computers. And what period mass storage hardware remains is likely to be both unreliable after several decades of neglect, and rather expensive if it works due to its rarity.

The Domesday Project 86 team face this particular problem to a greater extent than almost any others in the field, because their storage device is a particularly rare Philips Laser Disc drive. Their solution is the BeebSCSI, a small board with a CPLD and an AVR microcontroller providing host adaptor and SCSI-1 emulation respectively for a modern micro-SD card.

An original BBC Domesday set-up. Regregex [CC BY 3.0], via Wikimedia Commons.
An original BBC Domesday set-up. Regregex [CC BY 3.0], via Wikimedia Commons.
1986 saw the 900th anniversary of the Domesday Book, a survey and inventory of his new kingdom commissioned in 1086 by the Norman king of England, William the Conqueror. One of the ways the event was marked in 1986 was the BBC Domesday Project, a collaboration between the BBC, several technology companies including Acorn and Philips, and a huge number of volunteers from the general public and the British school system. Pictures, video, and text were gathered relating to locations all over the country, and the whole was compiled with a not-quite-hypertext interface onto a set of Laser Disc ROMs. The system required the upgraded Master version of the 6502-based BBC Micro, a SCSI interface, and a special Laser Disc player model manufactured by Philips for this project alone. The hardware was expensive, rare, and unreliable, so few of its contributors would have seen it in action and it faded from view to become a cause celebre among digital archivists.

There have been several resurrections of the project over the years, including one from the BBC themselves which you can browse online. What makes this project different from the others is that it strives to present the Domesday experience as it was originally intended to be viewed, on as far as possible the original hardware and with the original BBC Micro interface. Many original parts such as BBC Master systems are relatively easy to source in 2016, but the special Laser Disc player is definitely not. This board replaces that impossible link in the chain, and should allow them to present a glimpse of 1986 in more than just the on-screen information.

If you would like to see an original BBC Domesday Project system, you can find one in action at the National Museum of Computing, at Bletchley Park. Meanwhile we’ve already featured another peripheral from the same stable as this one, the SmallyMouse USB-to-quadrature mouse emulator.

24 thoughts on “SCSI Emulation Of A Rare Peripheral For The Acorn BBC Micro

  1. I worked at place that faces similar problems.

    The redtape and idiotic behavior of the people responsible is absolutely mind blowing. I spent a year designing and detailing a program to preserve the data seperate from the media and time and time again those assholes undercut my efforts for whatever greedy means they had.

    Last I heard, they’re on the verge of losing more than 50 years worth of data because they’re so worried about keeping the physical media they don’t realize the data is just rotting away.

    1. It’s got a bunch of digital innards that the standard Philips LV players didn’t. Unfortunately, the hardware is chronically crap in a similar way to the original Sony Playstation – the runner for the optics is relatively soft and wears over time, which stuffs the focus.

      At one point I had 3 of these machines (all reporting faults) and was only able to get to the state where they all showed the same ‘can’t focus’ problem.

      1. you can fix playstation worn out plastic groove by lining it with a thin metal strip, for example from a 3.5 floppy
        glueing in a thin sheet of plastic would probably work too, anything to make it stop wobble around

        1. Thanks for the tip. I bought a used PSX from Goodwill and it needed a replacement laser – I just bought one on eBay. No clue if it’s actually any better quality than the original.

          Also, firmware for some of the better MOD chips is now available online, and can be burned to a PIC… which I did… : )

          1. even 45 degree angle often “fixes” it

            all because cheap Sony figured plastic rail instead of steel rod (like in normal computer CD drives, or every single floppy drive) will be enough

  2. I used to have one of the original systems. I was part of a national project to develop the use of these systems in education, in schools and colleges. The quality of the video from the discs was excellent (for its day) and the ability to access frames, create menu controlled interfaces etc was ahead of its time. It was referred to as Interactive Video, because that’s what it was. I had every single disc commercially available for the system (around 100 if organic memory serves correctly), but one of the snags was the cost of having a disc made. In fact, I don’t think there were any purpose-made educational disc made at all. For education, the most promising disc for development, at that time, was The Doomsday disc, so that got big licks. . I remember the project with affection, but it was overtaken quite quickly by technology, which was changing rapidly at that time (as today, I suppose, but the leaps back then seemed bigger). It just shows yet another capability of the BBC Micro, and the foresight of the creators. Happy days.

    1. Back in the late 70’s, my friend’s Dad was a big shot at Philips HQ and they always had the latest tech gadgets at home like a VideoPac game console but also a LaserDisc player and a bunch of movies. I remember Jesus Christ Superstar, Jaws, Smokey & the Bandit and my favorite The Andromeda Strain. We had great fun watching the scary bits from Jaws in frame-by-frame mode. Good times!

  3. I’ve had a complete boxed Doomsday system stored for the last 25 years or so.
    I’ve powered it up twice, once when I got it and it all worked, and once again about 5 years ago.
    The second time the laserdisc was totally dead and the monitor wouldn’t sync.
    Fixing it is on the to do list but it needs so much desk space to set it all up I’ve not got around to it yet.

      1. Ah, no, i didn’t know it had a battery.
        I did check the Master years ago but didn’t even think there might be one in the laserdisc player.
        That could even be why it died i guess.
        I’ve repaired quite a few pcb’s over the years with leaking battery damage so i know exactly what you mean.

        Thanks for the pointer, i will have to get it out and have a look at it.

    1. BeebSCSI is actually 2 ‘independent’ parts – the AVR provides the SCSI-1 emulation (along with the G6 video control commands) and a Xilinx CPLD that contains a Verilog implementation of both the external (ADFS/Hard drive host adapter) and internal (VFS/AIV LaserDisc adapter). So you only need the BBC Master for it to work; but it is, therefore, more specialised than a generic SCSI-1 emulator.

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