[P2B] part two, question

hello,

I'm going to make some modifications to my motherboard as described on:
http://tipperlinne.com/p2b-ds150.htm

I have a question about 10K ohm resistor. There is used the term "The
10K ohm *programming resistor*". Since I'm not a professional I would
like to ask if this term ("programming resistor") refers to the resistor
of special type or not?

Would it be OK if I buy just "ordinary" 10K ohm resistor or I should
look for some specific one?

I would appreciate any response that will clarify that to me. I don't
live in US and I have to translate all terms used on the page mentioned
into local ones.

thanks,
geos

On Sat, 31 Jul 2004 09:18:35 +0200, geos wrote:

hello,

I'm going to make some modifications to my motherboard as described on:
http://tipperlinne.com/p2b-ds150.htm

I have a question about 10K ohm resistor. There is used the term "The
10K ohm *programming resistor*". Since I'm not a professional I would
like to ask if this term ("programming resistor") refers to the resistor
of special type or not?

Would it be OK if I buy just "ordinary" 10K ohm resistor or I should
look for some specific one?

I would appreciate any response that will clarify that to me. I don't
live in US and I have to translate all terms used on the page mentioned
into local ones.


In the shop: ask for FS3 programming resistor ! and see if they have
that and buy a: p2b soldering iron

Just an idea

best regards

John

In article , JK
wrote:

On Sat, 31 Jul 2004 09:18:35 +0200, geos wrote:

hello,

I'm going to make some modifications to my motherboard as described on:
http://tipperlinne.com/p2b-ds150.htm

I have a question about 10K ohm resistor. There is used the term "The
10K ohm *programming resistor*". Since I'm not a professional I would
like to ask if this term ("programming resistor") refers to the resistor
of special type or not?

Would it be OK if I buy just "ordinary" 10K ohm resistor or I should
look for some specific one?

I would appreciate any response that will clarify that to me. I don't
live in US and I have to translate all terms used on the page mentioned
into local ones.


In the shop: ask for FS3 programming resistor ! and see if they have
that and buy a: p2b soldering iron

Just an idea

best regards

John

Nyuk Nyuk Nyuk!

Of course it is an ordinary resistor. You can use any of several types,
whatever is available at your local electronics store. The value isn't
that critical. Like 5% is OK, 1/8W or 1/10W or even 1/20th of a watt
are safe power ratings. The only detail, is the form of the resistor,
either surface mount or through hole (axial leaded type). The resistors
on the motherboard are surface mount, and for this application SMT would
be the best if you can find some.

http://www.digikey.com (Enter P10.0KHCT-ND in the search box
The resistors are 10 for $0.90)
http://dkc3.digikey.com/PDF/T042/0914.pdf (link valid until catalog update)

The way this resistor is being applied, means it is named "programming
resistor" or a "strapping resistor". The idea is, a pin on an IC can be
used for two purposes, where one purpose exists at "T=0 seconds" and
the other purpose exists after that.

Let us draw a circuit...

+3.3V
+3.3V ---X |
10K |
X----/\/\/\---+ \ (Internal
"strap" | / 240K
GND ---X | \ Pullup
------------- | / Resistor)
| | |
| | | 22 ohm
PCICLK0 |----+--+--/\/\/\--------- Clock to PCI slot
| Series
| Damping
------------- Resistor ("R99")

When the circuit is running in its normal mode, PCICLK0 will be
enabled as an output. A square wave at 33MHz would be coming out
of that pin. The purpose of the 22 ohm resistor, is to match the
load at the end of the line, which in this case would be a PCI
plugin card. The sum of the output impedance of the pad, plus the
22 ohm resistor, is attempting to match the transmission line
impedance of the clock track. So, this is all that is needed of
the circuit, to do the normal stuff...

-------------
|
| 22 ohm
PCICLK0 |----------/\/\/\--------- Clock to PCI slot
| Series
| Damping
------------- Resistor ("R99")

Now, the other condition to worry about, is what happens at powerup,
i.e. when time is at zero seconds in the life of the IC. The PCICLK0
pin is not enabled to drive out at that time, and is instead an input.
It can sense a logic "1" as a 3.3V level, or a logic "0" as a 0V
level. The chip actually has a resistor of value 240K ohms inside
the chip, and the end of the resistor goes to +3.3V. This places a
weak 3.3V level on the pin, and that is the reason that no FS3 circuit
is required. So, with no modification to the circuit, FS3 always sees
a logic "1" caused by the weak (high resistance) internal resistor.

The high resistance is important. When the PCICLK0 is driving its square
wave, which is most of the time, the driver is so strong, it can
"override" the value the 240K pullup resistor was making at time t=0.
And, that is the trick of using "strapping" resistors, is the values
of the resistors are selected to "overcome" one another.

Our friend "P2B" has selected a 10K ohm resistor for a reason. It
is a stronger resistor than the 240K ohm resistor inside the chip.
When the 10K ohm "strap" is added to the circuit, and the other end
of the resistor goes to either +3.3V or GND, the 10K ohm resistor can
override what the 240K ohm resistor is doing. So, when a jumper plug
is used to connect the left hand end of the 10K ohm resistor to GND,
for example, the 10K resistor is saying to the PCICLK0 pin, "I want
a logic zero please". Since the 10K resistor is strong compared to
the 240K resistor, the 10K resistor "wins". There is actually a voltage
divider action, but I'm trying not to get too technical here.

But, of course, the PCICLK0 driver is much stronger than either the
10K ohm "strapping" resistor, or the 240K pullup resistor inside the
chip, so when the chip is finished initializing, the PCICLK0 will drive
out its square wave clock signal, and the other resistors just
"go along for the ride".

A detail that wasn't pointed out on the web site, is that another
function of the 10K ohm resistor, is it is separating the high
frequency part of the circuit (the "square wave"), from those nasty
long wires used to connect to the three pin header which is hot melt
glued to the PCB. It is important that the 10K ohm resistor be fastened
as close as possible to the 22 ohm resistor. The best resistor for
that purpose, would be a surface mount (SMT) resistor, of size
0603 or so.

This wire can be long.
|
|
v 10K
X----/\/\/\---+
"strap" |------ Keep this wire physically short,
| as it can upset the high frequency
------------- | signal.
| |
| | 22 ohm
PCICLK0 |----+-----/\/\/\-----

Surface mount resistors are not a lot of fun to work with. They
tend to stick by surface tension, to the tip of the soldering iron.
In this case, an SMT resistor could be reflow soldered to the
existing junction where "R99" is soldered to the motherboard.

Most hobbyists will have access to the older through hole resistors,
the axial ones with the wires sticking out of the end. These should
not be soldered directly to the board! The problem is, the wire on the
resistor is stiff, and after soldering is finished, if you accidently
put any stresses on the resistor (tugging), you can actually rip a
copper pad off the motherboard. I recommend using some thin wire,
such as 30 gauge wire wrap wire (kynar insulation is easier to strip
than teflon). The purpose of the thin wire, is it bends easily and
that wire will "give" first, rather than the copper pad.

The max stub I would have off that circuit, is perhaps 1/2". That
is the length of wire plus the lead on the resistor, as shown
in the above figure with the "Keep this wire physically short"
arrow next to it. That is why soldering an SMT resistor directly
to R99, keeps the equivalent wire length to well under 0.1".

If you feel these conditions are too difficult to meet, the
only downside of using longer wires at the 22 ohm resistor, is
that whatever PCI slot or PCI device is driven by PCICLK0, may
get misclocked. Simply not using the PCI slot it connects to is
one solution. However, if the PCICLK0 signal is used to clock
the Southbridge, then you must maintain the high frequency
quality of the signal, if you expect the board to boot.

The datasheet for the clock gen goes over some of these details.

http://www.icst.com/products/pdf/ics9250-08.pdf

So, now you know the "secret" of strapping ICs. Many ICs use
this same principle, of using output pins as inputs at time
t=0, and latching or sampling the value "strapped" to the pin
for that short time. As long as the "strapping resistor" is weak,
the normal output circuit never knows it is there.

HTH,
Paul

[snip]

HTH,
Paul

Great post Paul! Thanks! I've just returned from a local store with
necessary equipment. I hope I'll be able to post some more messages in
near future after my modifications to P2B-D

cheers,
Geos

In article , geos wrote:

[snip]

HTH,
Paul

Great post Paul! Thanks! I've just returned from a local store with
necessary equipment. I hope I'll be able to post some more messages in
near future after my modifications to P2B-D

cheers,
Geos

I was just checking the datasheet, and the internal resistor is a
pulldown on FS3, but the same arguments apply. Gotta proof read
these more carefully.

Paul

Paul, I have another question. What is a typical scenario when 10kohm
resistor losses its connection with PIN9 while motherboard is working
and FS3 is connected for example to get 124MHz and PCI@33MHz? Will P2B-D
go to heaven (or hell) then? If so, how does such sudden
disconnection affect PCI cards, processors, memory etc.?

Perhaps it may be useful to know "apollo13-like" procedure I couldn't
find it on the Internet..

cheers,
geos

In article , geos wrote:

Paul, I have another question. What is a typical scenario when 10kohm
resistor losses its connection with PIN9 while motherboard is working
and FS3 is connected for example to get 124MHz and PCI@33MHz? Will P2B-D
go to heaven (or hell) then? If so, how does such sudden
disconnection affect PCI cards, processors, memory etc.?

Perhaps it may be useful to know "apollo13-like" procedure I couldn't
find it on the Internet..

cheers,
geos

The "strapped" logic value defined by the 10K ohm resistor, the
three pin header, and the jumper, is only sampled at power up.
When the computer is running, the resistor can fall off if it
wants. You could pull the jumper, for example, and the clockgen
would continue to run as it had before. But I don't recommend
floating bits of wire on a motherboard, as if one of the wires
that connects to +3.3V or GND touches the wrong thing, there could
be big sparks :-)

If you don't feel confident in your ability to solder a SMT
resistor to the board, then get an axial lead 1/8th watt resistor
from your electronics store and use it. Place a 1/2" long piece of
30 gauge wire on one end of the resistor and twist it around
the resistor lead several times. Push the twists of wire
right up to the body of the resistor. Solder the twists in
place. Cut off the excess resistor lead off that end of the
resistor. Once the resistor has been prepared, with this flimsy
piece of wire on the end, hold the other end of the wire to
the R99 junction, and heat the junction until the wire is
immersed in the solder. If you "tin" the end of the 1/2" wire
first, it will solder easier to the R99 junction. As I said in
the previous post, the length of wire on your 10K resistor
should be kept short, where it meets R99. That is why I suggest
the 1/2" or shorter length. The 30 gauge wire mechanically
is weak, so if tugged there is less chance of damaging the
motherboard.

30 gauge bare Twists of wire around resistor lead.
wire | Solder the twists, then cut off the excess
| resistor lead
| |
| v 10K
| ((((-/\/\/\---------
v | ^
--------+ |
|
Run a wire from here to the 3 pin header.
Or just solder a wire on this end and
connect to +3.3V or GND, for a permanent
logic "1" or logic "0" strap. That is
less work than glueing on a header.

When you make any modifications like this, make sure the
components are secured to the board, so they don't fall off
and touch something. Cover any exposed wire with an insulator.
I like to use "heat shrink tubing" and keep several diameters of
the stuff available, and slide a piece over the whole resistor and
soldered joints. That way there is a little less danger caused
by the modification.

HTH,
Paul

Paul wrote:

The "strapped" logic value defined by the 10K ohm resistor, the
three pin header, and the jumper, is only sampled at power up.
When the computer is running, the resistor can fall off if it
wants. You could pull the jumper, for example, and the clockgen
would continue to run as it had before. But I don't recommend
floating bits of wire on a motherboard, as if one of the wires
that connects to +3.3V or GND touches the wrong thing, there could
be big sparks :-)

ok, so I understand that until a computer is on and the resistor falls
off "properly" :-) eg. without sparkles, it's fine.
but how about if it fall off in the way that I won't notice? I mean what
is the scenario when the resistor falls off (I don't know that it
happens), I turn off a computer, and turn it on again? There would be
the air instead of 10KOhm while FS3 connected altogether with FS0
modified. Would be that situation dangerous when I power the computer on
again?

If you don't feel confident in your ability to solder a SMT
resistor to the board, then get an axial lead 1/8th watt resistor
[snip]
soldered joints. That way there is a little less danger caused
by the modification.

I did something different. I bought a special kind of varnish that leads
a current (I'm not sure if this is that called in English) and 1/8th
watt axial resistor (very small one). I measured the length of its
connectors and cut them properly. Then and I glued this resistor with
tiny drop of special glue to the chip. One end of the resistor was
directly placed above PIN9 of the chip (less than 0.5mm in distance).
Then with magnifying glass I made the connection between the resistor
and PIN9 using the leading current varnish.

Do you think it is OK? I haven't made other connections yet, but I
assembled computer again and it works. At least I know that I haven't
connected for example pin9 with pin8 on the chip.

Now I would like to check if this connection is OK and leads the
current. Is is safe to put one pin of a digital multimeter before
connection and one after it (but before the 10kOhm resistor)?

I didn't have experience either in soldering SMT elements, nor I didn't
want to make holes in the motherboard. I thought that modifying the
motherboard with glue and varnish could be easily demounted if there
would be a need for it in future..

What do you think about this way of making modifications?

thank you for your responses, they are very detailed and helpful.
cheers,
Geos

In article , geos wrote:

Paul wrote:

The "strapped" logic value defined by the 10K ohm resistor, the
three pin header, and the jumper, is only sampled at power up.
When the computer is running, the resistor can fall off if it
wants. You could pull the jumper, for example, and the clockgen
would continue to run as it had before. But I don't recommend
floating bits of wire on a motherboard, as if one of the wires
that connects to +3.3V or GND touches the wrong thing, there could
be big sparks :-)

ok, so I understand that until a computer is on and the resistor falls
off "properly" :-) eg. without sparkles, it's fine.
but how about if it fall off in the way that I won't notice? I mean what
is the scenario when the resistor falls off (I don't know that it
happens), I turn off a computer, and turn it on again? There would be
the air instead of 10KOhm while FS3 connected altogether with FS0
modified. Would be that situation dangerous when I power the computer on
again?

If you don't feel confident in your ability to solder a SMT
resistor to the board, then get an axial lead 1/8th watt resistor
[snip]
soldered joints. That way there is a little less danger caused
by the modification.

I did something different. I bought a special kind of varnish that leads
a current (I'm not sure if this is that called in English) and 1/8th
watt axial resistor (very small one). I measured the length of its
connectors and cut them properly. Then and I glued this resistor with
tiny drop of special glue to the chip. One end of the resistor was
directly placed above PIN9 of the chip (less than 0.5mm in distance).
Then with magnifying glass I made the connection between the resistor
and PIN9 using the leading current varnish.

Do you think it is OK? I haven't made other connections yet, but I
assembled computer again and it works. At least I know that I haven't
connected for example pin9 with pin8 on the chip.

Now I would like to check if this connection is OK and leads the
current. Is is safe to put one pin of a digital multimeter before
connection and one after it (but before the 10kOhm resistor)?

I didn't have experience either in soldering SMT elements, nor I didn't
want to make holes in the motherboard. I thought that modifying the
motherboard with glue and varnish could be easily demounted if there
would be a need for it in future..

What do you think about this way of making modifications?

thank you for your responses, they are very detailed and helpful.
cheers,
Geos

If you are using a varnish or a conductive paint, then make sure
the components cannot move. Glue should hold them in place.

When using varnish, you would want to use the digital multimeter
and probe without touching the varnish. The varnish could be
easily damaged.

___/\/\/\____
X--R99--X-/ ^ \--X--- ...
|
^ Glue ^
| resistor to |
| board |
| |
Probe where there is a solid metallic
connection, without touching or stressing
the varnish.

Are you certain you want to do this ? If you have an electronics
repair shop, like a TV repair or a stereo repair, perhaps you
can bring the information on how to make the modification to
them, and they could solder the resistor for you.

Instead of the three header pins, you could also use a
single pole, double throw switch to select a logic 0 or
a logic 1. Use a hot melt glue gun, and glue the switch
securely to the motherboard, before taking the motherboard
to your local repair shop for the soldering.

/ Single pole, double throw
/
+3.3V ---------x x x-----------GND
|
|
10K
resistor
|
|
v
To R99

If you restrict your use of FS2, FS1, FS0 to the four combinations
marked as "Safe" below, then if the resistor falls off, the PCI
clock stays below or equal to 37.5MHz, so the disk won't get
corrupted on boot. The 115/38.3 probably isn't safe to use
anyway.

I have arranged the table below, so rows with identical FS2..FS0
are next to one another. If the resistor falls off, the setting
makes a transition from the left side of the table, to the
right (as FS3 has a pulldown to logic "0" as its default).

FS3 FS2 FS1 FS0 CPU PCI FS3 FS2 FS1 FS0 CPU PCI
1 1 1 1 133 33.3 0 1 1 1 100 33.4 Safe
1 1 1 0 124 31 0 1 1 0 133 44.3
1 1 0 1 150 37.5 0 1 0 1 112 37.3 Safe
1 1 0 0 140 35 0 1 0 0 103 34.3 Safe
1 0 1 1 105 35 0 0 1 1 67 33.4 Safe
1 0 1 0 110 36.7 0 0 1 0 83 41.7
1 0 0 1 115 38.3 0 0 0 1 75 37.5
1 0 0 0 120 40 0 0 0 0 124 41.3

By using only FS2..FS0 = 111, 101, 100, 011, you still
have access to 67, 100, 103, 105, 112, 133, 140, 150 MHz.
And, with those values, the PCI bus will always be less
than or equal to 37.5MHz, no matter whether FS3 is a
logic "0" or a logic "1".

Your varnish method makes me nervous :-)

HTH,
Paul

Paul wrote:

In article , JK
wrote:


On Sat, 31 Jul 2004 09:18:35 +0200, geos wrote:


hello,

I'm going to make some modifications to my motherboard as described on:
http://tipperlinne.com/p2b-ds150.htm

I have a question about 10K ohm resistor. There is used the term "The
10K ohm *programming resistor*". Since I'm not a professional I would
like to ask if this term ("programming resistor") refers to the resistor
of special type or not?

Would it be OK if I buy just "ordinary" 10K ohm resistor or I should
look for some specific one?

I would appreciate any response that will clarify that to me. I don't
live in US and I have to translate all terms used on the page mentioned
into local ones.


In the shop: ask for FS3 programming resistor ! and see if they have
that and buy a: p2b soldering iron

Just an idea

best regards

John


Nyuk Nyuk Nyuk!

Of course it is an ordinary resistor. You can use any of several types,
whatever is available at your local electronics store. The value isn't
that critical. Like 5% is OK, 1/8W or 1/10W or even 1/20th of a watt
are safe power ratings. The only detail, is the form of the resistor,
either surface mount or through hole (axial leaded type). The resistors
on the motherboard are surface mount, and for this application SMT would
be the best if you can find some.

http://www.digikey.com (Enter P10.0KHCT-ND in the search box
The resistors are 10 for $0.90)
http://dkc3.digikey.com/PDF/T042/0914.pdf (link valid until catalog update)

The way this resistor is being applied, means it is named "programming
resistor" or a "strapping resistor". The idea is, a pin on an IC can be
used for two purposes, where one purpose exists at "T=0 seconds" and
the other purpose exists after that.

Let us draw a circuit...

+3.3V
+3.3V ---X |
10K |
X----/\/\/\---+ \ (Internal
"strap" | / 240K
GND ---X | \ Pullup
------------- | / Resistor)
| | |
| | | 22 ohm
PCICLK0 |----+--+--/\/\/\--------- Clock to PCI slot
| Series
| Damping
------------- Resistor ("R99")

When the circuit is running in its normal mode, PCICLK0 will be
enabled as an output. A square wave at 33MHz would be coming out
of that pin. The purpose of the 22 ohm resistor, is to match the
load at the end of the line, which in this case would be a PCI
plugin card. The sum of the output impedance of the pad, plus the
22 ohm resistor, is attempting to match the transmission line
impedance of the clock track. So, this is all that is needed of
the circuit, to do the normal stuff...

-------------
|
| 22 ohm
PCICLK0 |----------/\/\/\--------- Clock to PCI slot
| Series
| Damping
------------- Resistor ("R99")

Now, the other condition to worry about, is what happens at powerup,
i.e. when time is at zero seconds in the life of the IC. The PCICLK0
pin is not enabled to drive out at that time, and is instead an input.
It can sense a logic "1" as a 3.3V level, or a logic "0" as a 0V
level. The chip actually has a resistor of value 240K ohms inside
the chip, and the end of the resistor goes to +3.3V. This places a
weak 3.3V level on the pin, and that is the reason that no FS3 circuit
is required. So, with no modification to the circuit, FS3 always sees
a logic "1" caused by the weak (high resistance) internal resistor.

The high resistance is important. When the PCICLK0 is driving its square
wave, which is most of the time, the driver is so strong, it can
"override" the value the 240K pullup resistor was making at time t=0.
And, that is the trick of using "strapping" resistors, is the values
of the resistors are selected to "overcome" one another.

Our friend "P2B" has selected a 10K ohm resistor for a reason. It
is a stronger resistor than the 240K ohm resistor inside the chip.
When the 10K ohm "strap" is added to the circuit, and the other end
of the resistor goes to either +3.3V or GND, the 10K ohm resistor can
override what the 240K ohm resistor is doing. So, when a jumper plug
is used to connect the left hand end of the 10K ohm resistor to GND,
for example, the 10K resistor is saying to the PCICLK0 pin, "I want
a logic zero please". Since the 10K resistor is strong compared to
the 240K resistor, the 10K resistor "wins". There is actually a voltage
divider action, but I'm trying not to get too technical here.

But, of course, the PCICLK0 driver is much stronger than either the
10K ohm "strapping" resistor, or the 240K pullup resistor inside the
chip, so when the chip is finished initializing, the PCICLK0 will drive
out its square wave clock signal, and the other resistors just
"go along for the ride".

A detail that wasn't pointed out on the web site, is that another
function of the 10K ohm resistor, is it is separating the high
frequency part of the circuit (the "square wave"), from those nasty
long wires used to connect to the three pin header which is hot melt
glued to the PCB. It is important that the 10K ohm resistor be fastened
as close as possible to the 22 ohm resistor. The best resistor for
that purpose, would be a surface mount (SMT) resistor, of size
0603 or so.

This wire can be long.
|
|
v 10K
X----/\/\/\---+
"strap" |------ Keep this wire physically short,
| as it can upset the high frequency
------------- | signal.
| |
| | 22 ohm
PCICLK0 |----+-----/\/\/\-----

Surface mount resistors are not a lot of fun to work with. They
tend to stick by surface tension, to the tip of the soldering iron.
In this case, an SMT resistor could be reflow soldered to the
existing junction where "R99" is soldered to the motherboard.

Most hobbyists will have access to the older through hole resistors,
the axial ones with the wires sticking out of the end. These should
not be soldered directly to the board! The problem is, the wire on the
resistor is stiff, and after soldering is finished, if you accidently
put any stresses on the resistor (tugging), you can actually rip a
copper pad off the motherboard. I recommend using some thin wire,
such as 30 gauge wire wrap wire (kynar insulation is easier to strip
than teflon). The purpose of the thin wire, is it bends easily and
that wire will "give" first, rather than the copper pad.

The max stub I would have off that circuit, is perhaps 1/2". That
is the length of wire plus the lead on the resistor, as shown
in the above figure with the "Keep this wire physically short"
arrow next to it. That is why soldering an SMT resistor directly
to R99, keeps the equivalent wire length to well under 0.1".

If you feel these conditions are too difficult to meet, the
only downside of using longer wires at the 22 ohm resistor, is
that whatever PCI slot or PCI device is driven by PCICLK0, may
get misclocked. Simply not using the PCI slot it connects to is
one solution. However, if the PCICLK0 signal is used to clock
the Southbridge, then you must maintain the high frequency
quality of the signal, if you expect the board to boot.

The datasheet for the clock gen goes over some of these details.

http://www.icst.com/products/pdf/ics9250-08.pdf

So, now you know the "secret" of strapping ICs. Many ICs use
this same principle, of using output pins as inputs at time
t=0, and latching or sampling the value "strapped" to the pin
for that short time. As long as the "strapping resistor" is weak,
the normal output circuit never knows it is there.

HTH,
Paul

Great post, Paul!

I always use a surface mount resistor because it's much easier to solder
directly to R99 than any other type - besides, they are plentiful and
free if you have a few parts boards lying around. I wet R99 with
no-clean liquid flux, hold the resistor (with tweezers) on top of R99 at
about a 30 degree angle, reflow the solder, then solder 30AWG wire-wrap
to the 'upper' end of the new resistor, and finally add a drop of
hot-melt glue for mechanical protection.

I've had email discussions with several modders who insist on installing
the programming resistor at the jumper instead of at R99 because it's
easier. It seems to work, but I won't do it for the reasons you describe
- if you have problems with PCI devices later, diagnosing a bad PCI card
vs. a degraded PCI clock signal could be a nightmare!

P2B