[time-nuts] Using a frequency synthesizer replacement for motherboard oscillator
hmurray at megapathdsl.net
Sun Dec 2 03:10:54 UTC 2012
davidwhess at gmail.com said:
> One of my favorite tricks back when the ISA bus was still available was to
> use a custom expansion board I built and an oscilloscope to measure the
> interrupt latency.
You can do the same trick without special hardware. Use the printer port.
Of course, that assumes your PC/Laptop still has a printer port.
I have a laptop with a printer port on the thing Dell calls a MediaBase.
It's an extender/fattener that includes a CD drive with connectors for
printer port and serial port. It plugs into a big connector on the bottom of
Many laptops plug into docking stations for use at a desk. Sometimes/often
they have printer ports and/or serial ports.
You could probably do it with just a serial port by flapping one of the
output modem control signals.
If you don't have a printer port or serial port, how are you getting the
interrupt into your box?
Many years ago, I helped a friend with this sort of thing. We were working
for DEC back in the days before Intel had captured everything and
workstations still needed lots of chips and chips had big pins so you could
get a scope probe on them. My part was to connect scope probes to the
interrupt line from the ethernet chip and the chip select for the MAC address
ROM. He patched the driver's interrupt routine to read the ROM.
These are my opinions. I hate spam.
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