High temperature protection for motherboards that don't have it?

[larrymoencurly]

I have an ECS K7S5A Pro Athlon mobo with a BIOS that doesn't seem to
have any built-in alarm functions to prevent the CPU from burning up
in case the fan stops. While I can use Motherboard Monitor for this
protection, I'm looking for something that doesn't depend on anything
as unreliable as Windows. But since I don't know how to patch a BIOS,
I want to add a temperature sensor to the CPU
heatsink and a circuit to short the jumper pins for the power-on
button (short won't hurt -- it's open collector). My questions are:

1. Do ATX computers always go into suspend mode when the power button
is pressed briefly?

2. In suspend mode, is the CPU always slowed way down enough to run
safely without a fan? I'd rather put the computer into suspend mode
rather than shut it down completely and crash any programs that were
running, but only if suspend mode is safe enough.

I'm not looking for hardware protection that can prevent damage if the
heatsink pops off, only if its fan fails.

 

[Kyle Brant]

|
|
| larrymoencurly wrote:
|
| > I have an ECS K7S5A Pro Athlon mobo with a BIOS that doesn't seem
to
| > have any built-in alarm functions to prevent the CPU from burning
up
| > in case the fan stops. While I can use Motherboard Monitor for
this
| > protection, I'm looking for something that doesn't depend on
anything
| > as unreliable as Windows. But since I don't know how to patch a
BIOS,
| > I want to add a temperature sensor to the CPU
| > heatsink and a circuit to short the jumper pins for the power-on
| > button (short won't hurt -- it's open collector). My questions
are:
| >
| > 1. Do ATX computers always go into suspend mode when the power
button
| > is pressed briefly?
| >
| > 2. In suspend mode, is the CPU always slowed way down enough to
run
| > safely without a fan? I'd rather put the computer into suspend
mode
| > rather than shut it down completely and crash any programs that
were
| > running, but only if suspend mode is safe enough.
| >
| > I'm not looking for hardware protection that can prevent damage if
the
| > heatsink pops off, only if its fan fails.
|
| I think shorting the 'power on' pin turns on the supply. I don't
think it
| will
| go to suspend

my k7s5a goes into a suspend mode if the power switch is closed after
the initial hardware ID and bootstrap process is completed (i.e., if I
have no boot disk or I boot to a DOS prompt). To power down, I must
reset or ctl-alt-del and hit the power button before the BIOS is
completed with it's initialization routines.

As to the proposed mod of the power on switch circuit, sounds to me
like it might work. I would suggest a reed relay in parallel with the
existing power switch connections, and a temp monitor circuit that
produces a pulse to activate/deactivate the relay. Another thought is
a simple op-amp comparator might work nicely, and some have open
collector outputs with enuf umph to drive a reed relay coil, I think,
it's been a while since I perused an IC databook. All you need then
is a voltage from your temp sensor and a simple resistor divider with
a pot to establish your "switch" point. The trick will be to produce
a 50 ms pulse to activate/deactivate the relay, as the mobo does not
go into suspend mode until the power switch is released.

 

[larrymoencurly]

I think shorting the 'power on' pin turns on the supply. I
don't think it will go to suspend

Thanks. I did some checking, and it turns out that a lot of BIOSes
don't always put the computer into suspend mode when the pins are
shorted briefly, and one BIOS even has a setting to prevent going into
suspend mode no matter what. So I think I'll just make the protection
device short the pins for at least 10 seconds to make sure that the
computer shuts down.

 

[larrymoencurly]

As to the proposed mod of the power on switch circuit, sounds to me
like it might work. I would suggest a reed relay in parallel with the
existing power switch connections, and a temp monitor circuit that
produces a pulse to activate/deactivate the relay. Another thought is
a simple op-amp comparator might work nicely, and some have open
collector outputs with enuf umph to drive a reed relay coil, I think,
it's been a while since I perused an IC databook. All you need then
is a voltage from your temp sensor and a simple resistor divider with
a pot to establish your "switch" point. The trick will be to produce
a 50 ms pulse to activate/deactivate the relay, as the mobo does not
go into suspend mode until the power switch is released.

I'm going to try to get by with just an LM339 quad comparator because
it should be able to handle both the thermistor and the latch for the
output (I've decided against just trying to put the computer into
suspend mode -- too many BIOSes allow it to be disabled), plus it has
open collector outputs, which is exactly what the power switch circuit
uses. But since I don't want to void any warranties in an obvious
way, I'm looking for a funny header pin connector that will let me
plug this circuit onto the mobo pins and then plug the regular power
button leads on top.

 

[Mike Tomlinson]

I have an ECS K7S5A Pro Athlon mobo with a BIOS that doesn't seem to
have any built-in alarm functions to prevent the CPU from burning up
in case the fan stops.

I don't understand this. I have a K7S5A with the Pro BIOS flashed, and
it has configurable audible alarms for CPU overheat and fan failure in
the BIOS setup.

 

[jaster]

"Kyle Brant" <[email protected]> wrote in message

I'm going to try to get by with just an LM339 quad comparator because
it should be able to handle both the thermistor and the latch for the
output (I've decided against just trying to put the computer into
suspend mode -- too many BIOSes allow it to be disabled), plus it has
open collector outputs, which is exactly what the power switch circuit
uses. But since I don't want to void any warranties in an obvious
way, I'm looking for a funny header pin connector that will let me
plug this circuit onto the mobo pins and then plug the regular power
button leads on top.

Have you tried the free MotherBoard Monitor 5 (MBM5) from
www.livewiredev.com ? It's a real time cpu and m/b temp and fan monitor
that you can configure to play beeps and shutdown at critical tempuratures.
I use it on my K7S5A to monitor temps and it's accurately reports temps.
This is a software solution instead of risky wirings but hey it's your cpu
and m/b.

 

[Jan]

The official 2003-01-20 BIOS on my K7S5A Pro offers no such options. Which BIOS version are you using? A HoneyX or Cheepoman version from the K7S5A forum?

Marc.

 

[larrymoencurly]

I'm going to try to get by with just an LM339 quad comparator
because it should be able to handle both the thermistor and the
latch for the output [to shut down the computer completely]

Have you tried the free MotherBoard Monitor 5 (MBM5) from
www.livewiredev.com ? It's a real time cpu and m/b temp and fan
monitor that you can configure to play beeps and shutdown at
critical tempuratures. I use it on my K7S5A to monitor temps
and it's accurately reports temps. This is a software solution
instead of risky wirings but hey it's your cpu and m/b.

Do you really think that I'd use *my* mobo as the guinea pig for the
prototype? Actually I'm going to first try it with a P4 mobo
since it's impossible to burn up those CPUs, but I'd really like to
make something that can protect the CPU even if the heatsink pops off;
unfortunately I don't know how to test this cheaply.

I've installed MBM, and it's great and a couple of times may have
saved computers when their power supply fans failed.