COW - Computer Originated World

[ppppenguin]

Golborne isn't doing agriculture This COW is the BBC's Computer Originated World. There quite a lot about it online, inlcuding a wikipedia page and several interesting links from there. https://en.wikipedia.org/wiki/Computer_Originated_World

The COW at the Broadcast Engineering Museum was used by BBC World. This COW was unwell, with intermittent problems as the globe rotated. I took it home with me to put on the bench. It weighs over 30kg and is a 9U (15.75") high rackmount unit.

The COW has about 300x 27128 EPROMs that contain runlength encoded data for the rotating globe plus another 112 EPROMs for the fixed data. There are 14 memory cards, each of which holds up to 32 EPROMs.

I don't have an extender board so it's tricky to work on the cards. Swapping sets of up to 32 EPROMs between cards was a horrible job, reduced to merely tedious when I found a pin straightener.

I won't go into details of the faultfinding (unless you insist) but both faults were failures in sections of 74LS377 chips. https://www.ti.com/lit/ds/symlink/sn74ls377.pdf The '377 is an 8 bit D-type register, less well known than the '374. The great thing about the '377 is that is has a clock enable and so can be used for proper synchronous logic design.

In one case I was able to swap an offending memory card to a slot where that chip wasn't needed. In the other, I cut tracks and used wire links to swap the offending section with another, unused section, on the same chip.

The COW has been on soak test for several hours and is mooing contentedly. 

I should add that I have previously overhauled the COW at the Dulwich museum. That didn't have any awkward digital faults, just a horrible bodge in the digital to analogue converter.

If anyone has a few 74LS377 to spare they would be much appreciated. I have a 74ACT377 in my store but AC and ACT series are a bit fast and hairy when there isn't a ground plane and really good decoupling.

[radioman]

Hi Jeffrey,
Very interesting piece of broadcasting history there.
I've got many types of 74LS & 74S TTL here, including some SN74LS377N.
PM me for details.

Andy

[ppppenguin]

I think I know of four surviving COWs. I've got EPROM data for the globe and two of the idents (South and Belfast). I could extract the BBC World data.

It would be possible to fit 27512 EPROMs in the ident slots with four different idents. Quite a lot of work and really not worth the effort.

The four surviving units are:
* Broadcast Engineering Museum (BBC World)
* Dulwich museum (South, I think)
* Privately owned by somebody I know. May come to the BEM in due course. (region not known)
* Privately owned by somebody who I was in touch with some years ago. Can't immediately find my correspondence. (Belfast, I think)

Somebody I'm seeing on Sunday thinks he has some odd boards from a COW.

[ppppenguin]

A big thank you to Andy (radioman) who has promised me some LS377s.

If anyone knows the whereabouts of some BBC "BMM" extender boards we would also be very grateful. Please see photos. The COW needs 4U and 5U. Other sizes may be useful for other kit we have at the museum.

[PerdioPal]

And just to think, today it can be done on a £10 hobby computer board.

[Richard_FM]

I remember the COW seemed to high-tech when it was launched in 1985, compared to the mechanical globes.

BBC1 had quite a big facelift around that time with Terry Wogan getting his 3 times a week chat show & EastEnders starting.

[Mike Watterson]

Though the mechanical one was black and white with colour by electronics. I remember they had it on a table with an old pedestal camera pointing at it in the corner of a small radio continuity announcers room in BBC Belfast (BBC NI). Maybe even a mono camera, is that possible? It lit up and spun by remote control. The back illuminated caption badge could fall off easily. I think about the size or two stacked shoe boxes or biscuit tins. The COW sounds bigger, but would take less space as there is no need for the camera!

I always though the curved mirror back was a strange idea. Anyone know who designed the original concept and the "why" of it.

I don't remember seeing 74xx377 ever. I still have some of the 74xx374.

[ppppenguin]

The camera used for BBC station ID etc was known as a Noddy: https://en.wikipedia.org/wiki/Noddy_(camera) Colour was inserted by a CoxBox or similar.

The '377 was indeed rare compared to the '374 but if you were doing proper synchronous logic design it was very useful as it had a clock enable pin. The later '574 and '577 had rationalised pinouts so that the signal flowed across the chip. LS series logic was barely fast enough to do useful stuff at the 13.5MHz clock rate of digital video. S series was fast but very hot and somewhat temperamental.

[Doodlebug]

Why not film a small painted World rotating globe ? Cheap, simple.

[Mike Watterson]

The camera used for BBC station ID etc was known as a Noddy: https://en.wikipedia.org/wiki/Noddy_(camera) Colour was inserted by a CoxBox or similar.

The camera for the globe in 1970s BBC NI was just a fixed one. Did nothing else. I'd heard of Noddy but never seen one.