Schneier on Security

Clive Robinson • January 10, 2024 2:30 PM

freeman k,

YYYYMMDDHHMMSS Is a recognized time string and befor Y2K approached it also had only YY rather than YYYY

Back when I was not just designing bits of super computers but also building them with a wire wrap gun and TTL logic chips on full EuroCards, RAM came in 256bit chips at over $10 so 1Kbyte of RAM cost close to $400 in parts. Don’t ask about the 32bit CPU made from high speed ROM for the microcode store and well the bit slice chips that made the ALU were beyond most pockets capacity even using $10 bills. Oh and runing it at 16MHz took some skill.

Which was a lot better than when I started out and RAM was over $1 a byte and ALU’s were made with LSI TTL.

One of the things I did was design specialised clock cards (don’t ask even though it’s decades since sold of as scrap it’s still technically hush hush, why I don’t know).

What you need to know is “Binary Coded Decimal” had two decimal digits in each byte and a byte held a single field of a “Date:Time” structure of,

YearMonthDayHourMinuteSecond,

Which was 6bytes with the extra bytes used confusingly as binary values. Importantly this used minimum CPU time to process several Real Time Clocks. Likewise it minimized record storage. So yup people did do things in ways that now might appear odd untill you realise what the resource limitations were at the time.

Even now telling people that quite a few computers actually have four clocks supprises them.

1, CPU ticks in micro or nano seconds.
2, Process time in count total of CPU ticks or cycles.
3, Local Wall clock time.
4, Remote clock time.

The last often used to sync up communications and needs in some cases –where one or both ends are mobile at speed– to be rate adjustable continuously. Thus gets driven by the likes of a DDS clock that has nano Hz fractionality (and setting up is done using oscilloscope Lissajou figures to display fractional phase change rather than the near useless frequency counters etc).