snafu said:
http://www.hardwareforumz.com/eform.php?p=291206
Unfortunately, with all other devices, cards, processor, RAM, etc,
disconnected I still cannot get to the BIOS screen. And in response to
Paul’s advice, I have changed the DIP switch settings to match the
frequency settings I used in my old motherboard (where the processor
and RAM used to be installed) and still I have no luck. So does this
mean I got stuck with a dead mobo?
Unplug the reset switch cable, in case the reset switch is stuck on.
The following is advanced advice, suitable if you own a voltmeter.
Otherwise, find a good computer shop, and see if they can breathe
life into it. YMMV. Caveat emptor. Etc.
*************************
I cannot see what Vcore regulator chip is used on the board. It
looks like it is 28 pins and up near the processor socket and the
top edge of the board. _If_ that is a HIP6019:
http://www.intersil.com/data/fn/fn4587.pdf
it would not take much to make that chip shut down. If the chip
senses overcurrent, it will only make three tries before it
gives up and shuts off. Now, why that would be happening, is a
good question.
In any case, if you own a voltmeter, you could try probing to
see whether any voltage is present on the output. On page 3 of
the Intersil document, you can see Q1 and Q2, Lout1, and Cout1.
In the upper left corner of the picture of the CUSL2 motherboard
in the manual, you can see seven capacitors (that would be Cout1)
and a toroidal inductor (that would be Lout1). I would probe
the leg of the toroidal inductor which is next to the seven
capacitors, as a way of sampling Vcore. See if, in fact, it
reads 1.7V when the board is powered. If it is reading 0 volts,
that means the regulator has shut down. Now, unfortunately, if
you just pull the processor out of the socket, the Vcore regulator
will also shut down, because there will be an "all 1's" code on
the VID signals. To test that Vcore is working properly, without
the processor being present, you would need to try a wire mod
in the S370 socket.
These are the two 900Mhz P3 processors I can find on the Intel site:
http://processorfinder.intel.com/scripts/details.asp?sSpec=SL4SD
http://processorfinder.intel.com/scripts/details.asp?sSpec=SL5BS
Page 21 of this document shows the Vcore table:
ftp://download.intel.com/design/PentiumIII/datashts/24526408.pdf
To make 1.7V, the code is 0111 for VID3..VID0. That means only
VID3 needs to be grounded in the S370 socket, to test Vcore
without the processor being present. On page 68, connecting pin
AJ37 (VID3) to AK36 (VSS) will put logic "0" on VID3. Use a bare
piece of wire, such as a strand of wire from an old lamp cord.
Make sure the copper is bright and shiny, to guarantee a connection.
Now, as that picture on page 68 is a view of the bottom of the
processor chip, think carefully about where that corresponds to
in a socket view. (I rotated and flipped the picture in
Photoshop, to reduce the chances of error.)
36 37 AJAK
______________ ______________
/ | | x . . | 37
/ x |AK | x . | 36
| Pin x|AJ | |
| View | | Socket |
\ Pg.68 | \ View /
\______________| \_________/
Now, again try to measure the voltage at the junction of
the toriodal inductor, where it meets the seven capacitors.
You should see 1.7V on the upper leg of the toroid. At
least that tells you Vcore is working, if it wasn't previously,
and could indicate the processor is presenting too much of
a load (i.e. is shorting Vcore or something).
Whether this line of thinking is valid or not, really depends on
what kind of regulator is used for Vcore. The regulators that
try over and over again to run, are less likely to be a problem,
than the ones that "give up" when they see an overload. The
HIP6019 is particularly nasty, because a fault on any output,
causes all outputs to shut off, making debugging where the
problem might be, very difficult. From the HIP6019 datasheet:
"All four outputs are monitored and protected against extreme
overload. A sustained overload on any linear regulator
output or an over-voltage on the PWM outputs disables all
converters and drives the FAULT/RT pin to VCC."
*************************
Paul
