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Copyright © 1998 by Fabian Pascal. All Rights Reserved
By Fabian Pascal
With increasingly faster systems, temperature control
is becoming becoming more important. Faster CPUs, buses, graphics
cards and drives generate more heat and require proper cooling.
Witness the plethora of Web information on a variety of increasingly
sophisticated cooling devices and techniques (all the way to cryogenics),
including sites dedicated entirely to this subject.
Temperature control requires temperature monitoring. Yet all
the cooling sophistication notwithstanding, the PC industry must
still get its act together on basic monitoring.
This article discusses monitoring requirements for a system and
offers some practical recommendations.
CPU Fans
Beyond 300MHz, CPUs in general, let alone overclocked ones, must
be properly cooled. Pentium II (PII) CPUs come with basic coolers
consisting of a heatsink and one fan. While for speeds of up to
300MHz they are sufficient, it is advisable to get a more powerful
cooler for faster CPUs.
The better PII coolers come with a bigger heatsink and two fans.
Tennmax's VIVA (www.tennmax.com),
for example, has a unique advantage, explained by Vincent Tzeng
of TennMax as follows:
"The interface material on the VIVA cooler is a TennMax
proprietary materials, T-Pad. It is highly thermally conductive
and will soften above 45 degrees Celsius, becoming "comfortable"
to enhance thermal conduction between the sink and the CPU, which
usually has "micro surface defects".
Those defects can trap air pockets between the mating surfaces.
The T-Pad becomes gummy when the temperature raises above 80-90
degrees. But unlike many other "phase change" materials,
it will retain its physical integrity under high pressure and
high temperature (way over 100 degrees Celsius). It will, however,
revert back to its original elastomeric state when the temperature
falls back to 40 degrees or lower, so when the user removes the
cooler off the CPU, there is a clean break and no need to reapply
the interface material."
Overclocking, however, requires larger heatsinks and fans, such
as, for example, those of Global WIN's VEK-12 cooler (www.globalwin.com)
and there are even larger coolers with three fans.
But even with an effective cooler, not monitoring the CPU fans
is risky, particularly on Slot 1 boards, which make the CPU temperature
monitoring itself less likely (see below).
As a concrete example, when the CPU fan connector on my system
board failed for an unknown reason, both the cooler's fans stopped
working. Luckily, I had to open the case for another reason and
happened to notice it (although I do not know how soon after the
problem occurred I noticed it). This could have damaged the CPU
even without overclocking, but I was running a "Klamath"
PII/300 at 100x3.5=350MHz at the time, overclocking both it and
the bus! A fan monitoring facility would have issued an alarm
when the fans stopped. Even if the CPU temperature were monitored
-- it wasn't -- this would be safer than waiting for the temperature
increase to trigger an alarm.
System boards provide only one connector for the CPU cooler, to
which both fans must be connected with one wire. That means that
if one of the fans fails (which is what Murphy's law says will
happen), a monitoring facility won't detect it. The VEK-12 can
be connected to either one, or two places on the board, if they
are available and within reach (which may defeat the monitoring
of a case fan, see below) .
Coolers for Super7 CPUs (e.g. Cyrix MII and AMD K6-2), such as
TennMax's Ultra -- have only one fan, but monitoring is not guaranteed
(see below).
Case Fans
All cases come with a power supply fan, but vary on the number
of additonal fans, how many are standard/ optional and whether
they connect to the system board (3-pin) and can be monitored,
or to the power supply (4-pin) and cannot be.
For example, California PC Products's minitower case (www.calpc.com),
has two optional fans in front, under the drive bays, which normally
connect to the power supply; fans connecting to the system board
are available, but must be ordered explicitly. AProImage's tower
case (www.aproimage.com)
has three fans, one standard on the back, above the power supply,
and two optional in front, under the drives, but they all have
power supply connectors. Other cases I've seen accept two optional
fans with power supply connectors, or take up to five optional
fans, four on the sides of the drive bays (two on each side) and
one in front, but only one can be ordered with a system board
connector that can be monitored.
As far as I can tell, the standard power supply fans come with
4-pin connectors and, therefore, unless the vendor agrees to provide
a 3-pin connection, they cannot be monitored.
Drive Fans
Proper air flow and cooling must be provided for 10,000rpm hard
drives (and is advisable for even 7,200rpm), even if only to prolong
their lives; a $20-$35 expense for a drive cooler to protect a
>$600 drive certainly makes sense.
Tests of the various drive cooling devices available suggest that
their effectiveness is similar and they vary mainly in looks,
installation and price. California PC products offers the basic
BayCooler, which has two front fans and a grilled bezel which
makes it more esthetically pleasing.
Global WIN's KingKong is not as pleasing to the eye (the front
fans are exposed), but has three fans and its black metal enclosure
also serves as heatsink, for better heat dissipation. They also
offer the I-Storm, which is quieter and also helps circulate the
air in the case, but it protrudes from the face of the case (
the California PC case has a door and cannot be closed with it
installed).
The fans on drive coolers comes with 4-pin connectors and cannot
be monitored. The less esthetical fan exposure of the King Kong
enables visual detection of fan failure. Other than that, the
user must hope for the best (see conclusion).
System Board Fan Support
System boards vary on the number of fan connections they allow,
as well as on their location. Abit's BX6 board (www.abit-usa.com),
for example, has three fan connectors, one near the CPU, one between
the CPU slot and the RAM DIMMs, above the power supply connector;
and one on the corner underneath the DIMMs. Since the power supply
fan does not connect to any of them, this allows for two case
fans to be monitored (or one, if two CPU fans are monitored).
The fans that came with the California PC's case had 4-pin connectors,
but luckily my integrator, Digital Systems Innovation (www.dsi2000.com
), had a 3-pin replacement with enough wire to reach one of the
connectors; but not the other. Besides, when the CPU fan connector
went bad, I had to use the other connector for the CPU, so I ended
up monitoring only one case fan.
Abit's newer BH6 system board has only two fan connectors, of
which one is available for a case fan. But the board is a tad
smaller, just enough for the 3-pin fan's wire not to reach it
anymore.
The AOpen AX59Pro Super7 board (www.aopenamerica.com)
comes with a 3-pin connector for only one fan, on the corner under
the ISA slots.
Monitoring Software
Even if there are enough connections for all the fans on the system
board and all fans have 3-pin connectors that reach the board
(which is not likely), monitoring is still not guaranteed.
There are several monitoring programs available, some of which
do not work under NT. Of the couple of NT-compatible programs,
I prefer MotherBoard Monitor (www.euronet.nl/users/darkside/mbmonitor),
for its features set and user interface. It resides in the system
tray and is capable of monitoring system voltages; four temperatures:
CPU, system board and two other user- defined sensor locations
(see below); and the speeds of three fans (see Figure 1)
Figure 1: Motherboard Monitor
But to do their job, such programs must access special chips on
the system board, which vary across boards. MotherBoard Monitor
supports the LM78, LM75, LM79, or Winbond chips. According to
its developer, Alex van Kaam:
"Originally, Socket 7 system boards had the LM78 chip
connected to the ISA bus and the LM75 connected to the system
management bus (SMB). (LM79 is a LM78 with some smaller changes).
The LM78 can monitor one temperature, three fans, five positive
voltages and two negative voltages; the LM75 can monitor just
one temperature. Since the CPU was on the board itself, it was
easy to just put a LM75 sensor underneath it to compensate for
the thickness of the CPU.
When the Slot 1 systems with the CPU off the board came out, the
LM75 got dropped. At that same time, Winbond developed their W83781D
chip, which was nothing more then a LM78 with two more banks which
point to the possible location of two LM75 sensors. Thus, instead
of having to access the SMB and search for these sensors, monitoring
programs can now let the Winbond chip do it and read the results
of the two extra sensors from the chip. This, however, still applies
to Socket 7 boards only.
Then manufacturers came with the idea of temperature sensors on
cables (which are available for purchase). With Winbond, the first
extra sensor can be connected to the CPU, the second to the power
supply, or against the chip on the graphics card, or the hard
drive, etc. The sensors will report the temperature to the chip,
which can be read by software."
The BX6 (and BH6) boards implement the LM79 chip, which means
that the CPU temperature cannot be monitored. The Super7 AX59Pro
board, implements a Genesys Logic chip (www.genesyslogic.com),
which is not supported by MotherBoard Monitor. It comes with its
own monitoring utility from AOpen, which does not work under Windows
NT. A version downloadable from the Genesys Logic site doesn't
either. Thus, for all practical purposes, no fans can be monitored
with this board under NT.
Conclusions
System boards should provide two fan connectors for the CPU cooler.
Ideally, there should be at least three connectors for case fans.
In the absence of standard locations, one should be close to the
power supply and at least two should be as close to the drive
bays as possible. Fan wires
should be long enough (30-50" preferably) to reach any location
on any board. However, since an increase in the the overall case
temperature from fan failures is not as critical as that from
a CPU fan failure (particularly with overclocking), monitoring
the case temperature and less than all fans is acceptable.
In addition to the power supply fan, cases should have at least
two additional fans standard. All should, at least optionally,
be available with 3-pin connectors. Standard case locations for
fans are desirable, such that the location of connectors on the
system board can also be standardized.
System board makers should implement chips that allow for monitoring,
at the very least, of two temperatures -- CPU and system board
-- system voltages and at least two fans (CPU), but preferably
more. Chip standardization is desirable.
As things stand, users must take factor complications into account
when choosing system boards, cases and cooling/monitoring devices.
* check (a) which monitoring chip and (b) the number and locations
of fan connectors implemented by the system board and, all else
being equal, prefer one with more fan connectors and the Winbond
chip, or at least one which is common and thus supported by monitoring
software
* use MotherBoard Monitor, or equivalent software to monitor
your system; there are instructions on the Web on how to monitor
CPU temperature via the Winbond chip, by installing sensors; without
the Winbond chip, you can get a device such as ThermAlarm (www.gsconline.com),
that combines a set of user-placeable sensors with its own monitoring
software
* order as many fans with 3-pin connectors as the system board
supports and the rest with power supply connectors (any excess
3-pin fans you won't be able to connect at all); make sure the
wires of the 3-pin ones reach the connectors on the board )
(I would like to thank Alex van Kamm, Vincent Tzeng of Tennmax
and Chung Bao of Acadia Technologies for help with this article)
Copyright © 1998 by Fabian Pascal. All Rights Reserved