the actual RTC on modern (Intel based) PC's is driven from a standard 32,768 Hz crystal attached to the PCH. some of them are in incredibly small packages now instead of the old tuning fork-in-a-can ones. peeling off the load caps and crystal from the board would allow you plenty of spaces to tack down a lead from an external synthesizer.
-Eric On Fri, Nov 30, 2012 at 3:04 PM, bownes <bow...@gmail.com> wrote: > It all depends on what clock your talking about. Any given PC probably has > more than one oscillator onboard. > Generally there will be one for the CPU, one for the display circuitry, > and probably one for the real time clock. > > Presuming you are talking about the CPU clock, it should be fairly > straightforward to find the oscillator package on the motherboard find the > pin with clock output and feed your clock input there. > > On Nov 30, 2012, at 16:59, Bob Camp <li...@rtty.us> wrote: > > > Hi > > > > It's most commonly done with things like a Soekris 45xx series board. > You don't need anything very exotic for the frequency conversion. The > jitter in the PC is way worse than what the external chips will be creating. > > > > The real question is - what is the "magic frequency" on the particular > mother board you are going to modify? Once upon a time they all were a > pretty predictable 14.xxx MHz. These days, who knows what's going in where… > > > > Bob > > > > On Nov 30, 2012, at 4:55 PM, Sarah White <kuze...@gmail.com> wrote: > > > >> Has anyone ever used a TAPR clock block or other frequency synthesizer > >> to sort the clock drift / timing problems on a regular computer? I'll > >> probably end up with a used dell or IBM workstation for this purpose. > >> > >> Recently, I came across a low-cost frequency synthesizer capable of > >> using a 10mhz frequency reference (planning on using the thunderbolt > >> GPSDO I'm working with once I manage to sort out the temperature issues) > >> > >> http://www.tapr.org/~n8ur/Clock-Block_Manual.pdf > >> > >> ^ TAPR "Clock Block" has an installation example for how to do what I'm > >> planning with a Soekris net4501 low-cost / low-power embedded device... > >> > >> What I'm hoping to figure out is how to do the same, except on a proper > >> computer such as the local used ones I'm able to get for less than $200 > >> with 2ghz with 30GB hard disk, 512mb or more ram, etc. So I figure this > >> should be fine for what I'm planning. > >> > >> Example of what I'm trying to do, though based on the low-power embedded > >> Soekris net4501 system from the TAPR manual's example section: > >> > >> http://www.febo.com/time-freq/ntp/soekris/index.html > >> > >> ^Aren't those the photos from clock block frequency synthesizer manual? > >> > >> Again, I'm wondering if anyone has opinions or experience about doing > >> such things with NOT an embedded system (as I said, can get a nice 2ghz > >> or so machine for less than $200 locally at a brick and mortar shop > >> within walking distance) > >> > >> Thanks in advance, > >> Sarah > >> > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Eric _________________________________________ Eric Garner _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.