2008/8/18 Richard Peurifoy <[EMAIL PROTECTED]>:
> The Timer Units are based on the S360 timer which was a word in low > storage (80 X'50'). It was updated based on the line frequency (60 hertz > in the US). It does not change with the speed of the CPU, and so is > constant. The Timer no longer exists (replaced by the TOD clock), but > the TU still lives on in lots of software. To be even more detailed, the timer was a fullword binary integer defined so that bit position 23 represents 1/300 of a second. This is a convenient number to allow driving the clock based on either a 50 Hz or 60 Hz line frequency, depending on the local power conventions, but in practice only the smallest S/360s actually used the power line for the clock. While the actual S/360 timer counted down to zero, a quantity of timer units representing an elapsed or CPU time can be easily manipulated in any programming language using the conversion factor. There is nothing magic about timer units; they can be converted into a more suitable unit such as seconds or microseconds in the same way that funky units like furlongs or gallons can be converted to km or L. The quantity of what's being measured doesn't change. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
