How to use a multimeter to test Athlon XP unlocking?

[Wolfcastle]

Hi

I am particularly interested in testing with a multimeter. I've looked at Tom's Hardware as well as another site about how the multimeter should be used.

There are apparently 2 ways to test:

1. Connect the dot on the other side of the core to the lower L1 dots.

2. Connect both the upper and lower L1 dots.

In both of these tests, what are the results I'm looking for in terms of resistance?

And what would be a good example of a multimeter reading where the unlocking procedure was done incorrectly?

 

[johncar]

Wolfcastle,
Do not probe "directly" on the unlocking material as that does not check the "connection" below, and will most likely destroy your hard won connection/s. So best to probe from the socket pin connected to each L1 bridge...to the "L3/L4/L10 bridges end" of the 1K resistor that is connected to the closed bridge of the open/closed "bridge pair" itself
connected to the L1 bridge being probed. This will give a "direct connection" reading that you can evaluate.

You will find detailed circuit diagrams and all the information you need to properly locate the multimeter probes for each of the 5 L1 bridges at http://www.beachlink.com/candjac/index.htm link to Final Decoding Palomino article, (and other articles if interested).

Theoretically you should get a very low resistance reading less than 1 ohm, but in part because of the very fine internal traces we got readings of 1 or 2+ ohms. However, as a practical matter, because this resistance will be in series with the 1K protective/current limiting resistor, thus creating a "voltage divider", any resistance within 10% of that resistor's 1K value should not affect the abilty of the "comparators" in the Multiplier to interpret the HI or LO correctly as a HI or LO. Comparator circuits are very liberal in this regard, 90% of a spec HI's voltage is still interpreted as a "Logical HI", and 10% of a spec HI's voltage is still interpreted as a "Logical LO", (same as 0.0V = a hard ground. Comparators become "indeterminate" when the signal voltage changes to about 50% of spec, (because of problems like voltage division), which translates into resistance in question approx = 1K ohms.

So that gives you a theoretically workable range of 10% of 1K = 100 ohms for the resistance from a socket pin across its closed L1 bridge and its closed L3/L4/L10 bridge to the top of the 1K bridge...all directly connected. But we'd prefer that that resistance were closer to 10 ohms or less...which should be no problem with good connections at L1 bridges.

You might also test from the socket pins to "ground" since we understand that there are "grounded dots" in the opened L1 "slot" which might get connected to the L1 closing material if not done properly. Grounded L1 bridges will wreak havoc with oc'g. The link will also show you where to probe for "ground"...primarily at the bottom/signal feed end of the (5) 1K resistors connected to Ground. Note that for L1 bridges cconnected to signals set LO/grounded by default, the reading will be 1K ohms+...while you will be testing for direct shorts to ground/very low resistance.

Hope this helps, site has lots of signal circuits' detail.
John C.