PC power supplies (the Joy of Standards)

[Bob Eager]

I was given some core this week! Looks like 512 bytes (except it wouldn't have been bytes)...64 x 64 AFACS. From an Atlas, no less....anyone have any tech info???

[dennis]

The new "universal" ones have a removable portion that you don't use on older motherboards. The latching mechanism should align.

[CWatters]

The Ladybird guide to core store (1971)....

[Andy Burns]

Actually some laptops now use +/- 5V (presumably using a DC->DC converter) instead of +/- 12V on their serial ports, most equipment is happy with the reduced voltage swing but some isn't, this makes those laptops less useful as a roaming terminal for diagnosing problems on "random" routers/switches :-(

[Bob Eager]

specifics...

(later..)

'S OK....this is *exactly* what I have...

[John]

Which bit of GEC were you with Andrew? I spent one summer around the late sixties in Coventry Telephone works car park, building mobile telephone exchanges destined for Iraq. Even in those days exchanges were blown up and a mobile would be driven in and cabled up so minimising disruption.

[CWatters]

Well yes that was kind of tounge in cheek.

I worked at GEC Computers in Elstree from 1981-1984. I can't really remember for sure but I think they were still supporting (possibly even making?) core store memory cards for military computers of the day.

[Ian Stirling]

There are many, many chips that provide RS232 ports from one +3V or one

+5V rail.

[Chris Hodges]

A decent PSU doesn't worked plugged into a dell mobo. A cheap PSU never works again after being plugged into a dell mobo. Guess how I know! Pinouts are on the web if you don't mind a bit of soldering (splice the cables from the new PSU to the old connector)-

will have the ATX specs.

[Bob Eager]

Sorry!

I understand that every IBM employee (no matter who) was given a copy of that book at some point in the past...

I have used machines with core, but not for a while. Nice to have an example, and a fairly historic one at that...!

[Chris Hodges]

You're lucky to get serial on a laptop at all these days (but at least the keyspan USB-serial adaptors seem to work).

[Guy King]

The message from "CWatters" contains these words:

I downloaded a copy of this

few days ago. Allegedly some of it is "highly dangerous". Well, I suppose some of it is, but with a bit of common sense (avoiding the carbon tetrachloride experiments, for a start) it's mostly OK. Certainly more fun than the stuff you get these days.

[Sn!pe]

Back in the early '70s I used to fettle DCC minicomputers, which were "Chinese copies" of DEC PDP8s (one of the last minicomputers to still require two PCBs for the processor), and they used ferrite core store. We used them to drive our key to disk data-prep kit. One day I had removed the protective covers from one of our spare core-planes (something I'd done when fixing core store on my first mainframe), just so that I could have a really close look at the cores and wiring.

To do this I was using a jeweller's loupe, which very unfortunately popped out of my eye-socket and bounced on the middle of all that intricate lacing, shattering several dozen of the fragile toroids themselves and rendering the whole thing utterly useless. Was my face red when I confessed to my boss. Fortunately he took it in good part and slipped it back into stores without an explanation as to what exactly was wrong with it; just as well, those things were pretty costly.

[Jules]

OK, so I asked...

Apparently the original 16-64K IBM PC motherboards used 4116 memory chips which *are* 3-rail devices, so I was having a brain fart... (I'll have to check my original PC when I'm back in the UK to see what it has)

Anyway, so that's why -5V is there...

cheers

Jules

[Jules]

Don't the Science Museum have an Atlas? We've got a whole stack of Pegasus manuals, but AFAIK no Atlas documentation.

Word lengths were often *really* oddball on the older machines - usually somewhere up in the 30-80 bits range, and often odd numbers too. Our Elliott's 39 bits IIRC, and I think the Marconi is 40. 64 bits is certainly possible.

cheers

Jules

[CWatters]

Ah I remember when companies had component stores....and a little man in brown overall to run them. However did we manage without RS Components and overnight delivery? One of my first projects after leaving university was to build a memory card for a small data logger. The store only had 7 one bit wide memory chips and a jobsworth in stock. By the time I'd done all the necessary paperwork to order the 8th bit and then waited for it to be delivered .... I'd left the company..

[CWatters]

A lot of the early memory cards had error correction on them so it was frequently wider than the processor.

[CWatters]

Actually it's quite hard to find a laptop with a serial port built in now.

[dennis]

Why didn't you just use two nibbles?

[Andy Wade]

Interesting... which Elliott have you got? The 803 was the first computer I ever used. 39 bit words indeed, with two instructions per word: octal op codes, 16-bit absolute addresses and a modifier bit in the middle for indirect addressing (referred to as the B digit). 5-hole paper tape, or the keyboard push-buttons, for input and tape punches or a Creed 75 teleprinter for output. 8K words of core, mercury delay line registers and its infamous Algol 60 compiler. A fine machine :~)