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Gary C

World of IBM, Intel multibus plus a new PDP 11 !

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My PCW9512 is sort of working and the Gotek is installed and was at a bit of a loss what to do next

I managed to obtain a rack mount Micro PDP-11/73 that will need some care before powering up, but also saw a basket case 5160 on Ebay that was near enough to go and pickup, so went for it and now its mine

The front bezel is split in two and the case is bent on the right hand side, just where the Hard Disk is , so that unit is very suspect, but hey ho.

Its extremely dirty inside, 35 years of dust and dirt now cleaned away and everything looks in good condition. PSU stripped and cleaned and runs fine, right up until its connected to the motherboard then it shuts down . Ok after getting advice from this wonderful forum and reading the Hardware reference manual, it seems as if the PSU is shutting down because the motherboard is pulling the power good signal down. Suspect a tantalum capacitor, just need to do some testing to try and find out which one.

In other news, I have a PSU, back plane and card frame for my two multibus cards, but have been looking for a case that looks sufficiently 'vintage'. Found an old MOD case on ebay and now frame and PSU installed in case and almost look as if designed for it.
While I used to work on the multibus systems at work, mainly as a programmer, I never noticed that the 286 systems bus arbitration is different from the 8086 units. i knew the 286 units use bus arbitration PROM's but hadn't clocked that the 8086 use a more usual serial system passing the bus request down the backplane. The backplane also came without the local bus extension to allow the memory card to be used, however the LBX is a simple matter of making up a circuit board with each pin connected to the same pin on the next card. After some more digging though, it looks as if the 286 board can use serial and parallel bus arbitration so I should be able to use it with the standard Multibus I that I have.

Just need to cut some holes in the case to fit the PSU and Multibus cooling fans, then need some exciting buttons and flashing lights to liven up the front panel and some smoked perspex give a window onto the cards in the frame

It came with the standard Intel monitor EPROMs so I should be able to get a terminal connected up to the serial connector to see if it works, but then I might struggle with software, not sure I really need the ability to control a nuclear reactor at home.

At least it should look good.

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