On Sat, 18 Mar 2006 23:13:33 -0600, Alan C. Field <[EMAIL PROTECTED]> wrote:
>Eric, > >Almost I think. > >The Sysplex Timer is a big clunky box. It connects to a PC as it's >"console" > >We have a modem plugged into the PC that dials out to NIST. > >I think the CLO (CLOck?) card is the card in the processor that connects >to >the Sysplex timer. > > The CLO card is physically a card that installs in the timer. As I understand it, it enables the timer to receive time information from an outside source. I had to go back and dig out the old manuals I used a couple years ago to research this. >From "S/390 Time Management and IBM 9037 Sysplex Timer" SG24-2070-00 CLO = Control Link Oscillator "In the Expanded Basic configuration, a Control Link Oscillator (CLO) card is installed in the 9037. Therefore, this configuration has two advantages over the Basic configuration, described in 2.1.3, Basic Configuration on page 13. With this card installed, the 9037 can track to an External Time Source (ETS). Refer to 2.4, External Time Source Attachment on page 16 for more information on attaching a 9037 to an external time source. Secondly, the Expanded Basic configuration can be enhanced to the fully redundant Expanded Availability configuration concurrently, therefore not requiring any outage of operations." And my understanding of the function of the timer is to steer the onboard clocks on the processor. The processor clocks are always the source of time information. The timer compares the time from the external source to the time on the processor and either slows the clock down or speeds it up until they match. If you don't have a CLO card, the timer itself is the time source (your wristwatch is probably more accurate). You can't get more than four seconds out of synch or the timer won't be able to generate the proper steering impulses to get the clocks back in synch. There's lots of detail in the manuals if you care to attempt to understand it. ---------------------------------------------------------------------- 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
