-----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of R.S. Sent: Tuesday, May 22, 2007 1:20 AM To: IBM-MAIN@BAMA.UA.EDU Subject: Re: Synchronize Time Between Mainframe and Servers?
<SNIP> I don't know microwave owen design, but I can imagine a device working at - let's say - 3,5GHz +/- 20%. It can be fully acceptable for the device (like owen) to work at 4.2GHz as well as 2,8GHz. So, resolution is sub-nanosecond, but the accuracy is very poor. From the other hand quarts oscillators usually work at MHz frequency, but the frequency is very accurate and stable over time (months, years). <SNIP> Yes, we used to call that rock bound (Crystals) [I haven't had an FCC license at commercial or amateur level since about 1977 -- things change.] I'm told, but have no experience with PLL (Phase Locked Loop), that it is also as stable and into the GHz range. But let us get back on topic. The Mainframe's (at least from IBM's design), has a TOD that if it malfunctions, is detected and presented as a machine check. PCs, as far as I've been able to deduce, do not. As a result, the mainframe TOD has a design that prevents drift (or at least it did in the TTL days). So much so that in working on ETR designs it was questioned as to how dithering could be done without causing TOD error code giving failures. Obviously that microcode had to be changed to allow an external timer to make the changes w/o causing Clock Comparator errors (among others). Regards, Steve Thompson -- STD disclaimer: Poster's opinions are not necessarily those of poster's employer. -- ---------------------------------------------------------------------- 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
