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1. Why are there several types of heatsinks available for Pentium III and Celeron processors?

2. Where should the thermal grease be applied for proper cooling?

3. Is the AMD K6-III processor compatible with the 430TX chipset?

4. Can you explain how motherboard speeds relate to processor speeds?

5. Will the clock multiplier settings of a processor change according to the speed of the motherboard?

6. How are temperatures of the Pentium II processor monitored?

7. What do I need to do to overclock my CPU?

8. Why is my computer making high-pitch noises after I installed a new motherboard and processor?

9. Can you provide jumper settings for my K6 CPU?

1. Why are there several types of heatsinks available for Pentium III and Celeron processors?

Reader: I understand that there are different types of heatsinks available for the Socket 370 Pentium III/Celeron CPUs. Why is more than one type necessary?

Computer Doctor: The reason for different designs for heatsinks made for Socket 370 is because there are two different types of chip packages used for Socket 370 CPUs.

Intel has strict keepout requirements for socket 370, and any heat sink designers must follow those requirements to be compatible with socket 370. See the link below for more information. http://developer.intel.com/design/celeron/applnots/24441002.pdf

If you use a PPGA (Plastic Pin Grid Array) package chip such as the older Celeron in your socket 370, then you need a heat sink that is compatible with that chip. Likewise with the FC-PGA (Flip-Chip Pin Grid Array) package for the newer Celeron and Pentium III processors. Heatsinks for the PPGA package will not work with the FC-PGA package.

With FC-PGA a pedestal is required on the underside of the heatsink to clear the socket cam box. This is because the FC-PGA chip is thinner, and the surface of the chip is below the raised cam box portion of the socket. A heat sink with a flat base will NOT work.

Also, an asymmetric heatsink clip is required for the FC-PGA package. An asymmetric clip applies the load to the center of the exposed silicon die. A PPGA symmetric clip, which applies load to center of socket body, would place uneven force on the die and tilt the heatsink reducing thermal performance.

All heat sinks require a thermal interface material (i.e. a thin layer of thermal grease) between the heat sink and the back of the FC-PGA die. Here are some sites for companies that manufacture heat sinks for the FC-PGA Celeron/Pentium III:

http://www.wakefield.com

http://www.electronics-cooling.com/html/heat_sinks.html

My personal favorite is the patented Agilent ArctiCooler model CA. For more information see http://www.arcticooler.com and http://ftp.agilent.com/pub/semiconductor/arcticooler/haca0001.pdf. This is the highest performance heat sink currently on the market and fully conforms to the Intel Socket 370 and FC-PGA specifications.

2. Where should the thermal grease be applied for proper cooling?

Reader: I have a Thunderbird Athlon (Socket A) CPU. I'm confused about where to put the thermal grease for proper cooling. Can you help me?

Computer Doctor: Your CPU should look like the picture on page 207 Figure 3.56 (12th edition). The rectangular area in the center is the CPU die. The heat sink must make direct contact with this part of the chip, and there must be a very thin layer of thermal grease applied in that area only. Be sure the heat sink you have is properly designed for your chip. If in doubt, I recommend heat sinks from PC Power and Cooling such as the Z1-D for the Athlon/Duron. See the link below for more information. http://www.pcpowercooling.com/products/cooling/cpu/index_amd.htm

3. Is the AMD K6-III processor compatible with the 430TX chipset?

Reader: My computer has Socket 7 and the Intel 430TX chip set. I noted in your chapter on CPUs that the AMDK6-III (550MHz) fits into Socket 7. Can I buy the off-the-shelf version of the CPU and use it in my motherboard, or do I need an upgrade version?

Computer Doctor: There are several problems you might have in using the AMD K6-III CPU on your motherboard. The first problem is voltage. The K6-2 and K6-III require a lower voltage at the CPU socket than your motherboard probably supports. Most K6-2 and K6-III processors require 2.2V or 2.4V (depending on the exact model), and your board would be currently set to 2.8V (standard for Intel Pentium MMX). You can't use the K6 chips unless you are able to change the CPU socket voltage to 2.2/2.4V.

The second problem is bus speed. Your motherboard probably supports a 66MHz bus speed maximum. Some 430TX boards had "unsupported" speed settings of 75MHz, 83MHz, or even 100MHz, but most don't. BTW, if your system does support higher bus speeds, you could probably just change the bus speed from 66MHz to 75MHz and your current CPU speed would then automatically change from 233MHz (3.5x66) to 263MHz (3.5x75). In fact I have a system at home that is running that exact configuration. Most of the Intel 233 Pentiums I've encountered will reliably overclock that far. The good thing is that is a "free" upgrade, requiring only that you change the bus speed via the jumpers on your motherboard. Whether your board supports that, and how to do it is up to you. It may be an undocumented setting, or it may not be possible at all. Since I've never seen your exact board I couldn't advise further.

The bus speed problem relates to the K6 processors in that all of them past 366MHz require a 95MHz or 100MHz bus speed setting, and that is something your board probably doesn't support. So, based on voltage and bus speeds you are probably locked in to the Intel MMX 233 as the fastest CPU that will be a direct plug-in.

Still, all is not lost! There are companies making voltage regulator adapters that allow a K6 processor to be installed in a 2.8V socket. They then set the CPU to a higher than normal multiplier, and still work off of the 66MHz bus. Normally you purchase the CPU and adapter together in a single unit that then directly plugs into your Socket 7. Such a device is available from Evergreen Technologies at:

http://www.evertech.com/whitepaper/spectra400wp.asp.

The one I'd recommend is the "Spectra 400", which is essentially an AMD K6-2 400MHz processor mounted on a voltage regulator adapter board, pre-set to a 6x multiplier, and topped off with an active (fan) heat sink. This device will plug directly into your Socket 7, replacing the 233MHz Pentium MMX with what is essentially an AMD K6-2 400MHz. This costs about $130 and would be IMHO the best upgrade you could consider short of replacing the entire board, processor, and memory.

These devices should work with your existing BIOS, however if there are any BIOS upgrades available for your board, you should probably download and install them first.

4. Can you explain how motherboard speeds relate to processor speeds?

Reader: I don't understand motherboard speeds verses processor speeds. I have a 133 MHz motherboard and a 500 MHz processor. This confuses me; if the motherboard bandwidth is 133 MHz, then it can only "pump" information into the processor at 133 MHz. If you have a 500 MHz chip, a lot of the processor's bandwidth would seem to be wasted. Is that true?

Computer Doctor: You would think so, but since the processor "feeds" directly off the L1 cache memory in the CPU, and the L1 cache is running at the CPU speed of 500MHz, then the processor can run at full speed. Since most L1 caches have about a 90% hit rate, the CPU runs at full speed 90% of the time. Of the remaining 10% of time which are L1 cache misses, the CPU first checks the L2 cache, which also hits 90% of the time, and then as a last resort goes to main memory.

So... the typical CPU reads out of L1 cache 90% of the time, L2 cache 9% of the time, and main memory 1% of the time. Cache is the key to the ability for the processor to run faster the motherboard it is plugged into, and is also why main memory speeds have lagged tremendously behind processor speeds. If you could double the speed of your main memory, I'd say "congratulations!, you've doubled your speed 1% of the time!, gee I hope you didn't pay too much for that small an increase..." <g> Computer Doctor.

You'll note that the first processor to run faster than the motherboard was the 486, which was coincidentally (not!) the first processor with integral L1 cache.

5. Will the clock multiplier settings of a processor change according to the speed of the motherboard?

Reader: In your book you state that the processor operates at a multiple of the motherboard bus speed. Does this in fact mean that certain processors can only work with motherboards with certain speed, or will the clock multiplier settings of the proceesor change according to the speed of the motherboard?

Computer Doctor: A processor rated for a given speed is normally designed to operate at a specific multiplier and motherboard speed setting. You must make sure your board has the correct support for a given processor, that is it will supply not only the correct multiplier and bus speed settings, but that it will also supply the correct voltages and BIOS support. Contact your motherboard manufacturer for a list of the specific processors supported by a given board. Note that a BIOS upgrade may be necessary to allow your motherboard to support a given processor.

6. How are temperatures of the Pentium II processor monitored?

Reader: What method is used to monitor the temperature of Pentium II processors? The 'hardware monitor' in the BIOS set-up for my motherboard shows 'N/A' next to the CPU temperature. Why? I thought that the CPU case would have some kind of internal device for monitoring the temperature. Does it?

Computer Doctor: The Pentium II and Pentium III have a built-in temperature monitor, called a thermal diode, which is connected to pins B14 and B15 in the Slot 1 versions. Unfortunately not all motherboards have the requisite circuitry to read these pins, so on many boards they aren't connected to anything. Check with your motherboard manufacturer to see if your motherboard has the necessary on-board sensor to read this diode.  Intel describes a circuit that can be used on boards with or without the appropriate sensor to accurately monitor die temperature. Download and read the "Pentium III processor Thermal Metrology for CPUID 068h family processors" document at http://developer.intel.com/design/pentiumiii/applnots/245301.htm for information about a special adapter board you can get to add this capability to any system. This is used by system manufacturers to test and validate the thermal performance of their systems.

Another related document to check would be "Pentium III Processor Thermal Design Guidelines" document at http://developer.intel.com/design/pentiumiii/applnots/245087.htm.

An example of a motherboard that has the necessary on-board circuitry to read the diode is the Intel VC820 board. You can read more about this board or download documentation on it at http://developer.intel.com/design/motherbd/vc/vc_ds.htm.

7. What do I need to do to overclock my CPU?

Reader: I'm interested in experimenting with overclocking. What are the factors that control CPU speed and how can I change them to make my CPU run faster?

Computer Doctor: There are two factors that control CPU speed, the speed of the motherboard bus and the internal multiplier in the CPU. Motherboards may have multiplier settings, but these settings merely "tell" the CPU what to do, and the CPU is free to ignore those settings if so designed. Most Intel processors come with the multiplier locked, so that if you do change the multiplier setting on the motherboard, the CPU will simply ignore it.  That leaves bus speed changes as the only reliable way to overclock. Starting with the Pentium II Intel designed it such that the CPU "tells" the motherboard what the bus speed (and voltage) should be via two pins called BSEL0 and BSEL1. Motherboards can however include override capabilities for these settings, which will ignore what the CPU says and set the bus speed (or voltage in some cases) to whatever you want. Unfortunately, Intel's own boards do not allow this type of "hot rod" control, and you are left stuck with the default settings dictated by the CPU. If that is the case with your board, then you would have to make modifications to the processor or the motherboard circuit to "fool" the board into selecting 100MHz or 133MHz. This type of surgery is normally not recommended. If you think your board has the ability to set the bus speed either via jumpers or via the BIOS Setup, then you could try any available alternate settings to see if higher speeds are the result.

For your next system, if overclocking is something you would be interested in, I recommend you choose your motherboard with that in mind. Many review sources for ATX motherboards discuss overclocking issues. You'll find that BIOS-controller overclocking is much easier than opening the case and fiddling with jumper blocks.

8.Why is my computer making high-pitch noises after I installed a new motherboard and processor?

Reader: I recently upgraded my motherboard and processor. When I powered on my computer, I began hearing a high pitched tone coming from the computer. My only recourse to get it to stop is to shut down all programs, and shut down Windows. During the boot up process, after POST, it will make the same high pitched tone for awhile in DOS until WIN98 comes up, and then it will cease. As I work on the computer for awhile and then at odd intervals, seemingly related to nothing I can see, it will begin the tone again. And I must shut down to get rid of it.

Computer Doctor: The first thing you need to know is exactly where the sound is coming from. If it is coming from your speaker then you have a defective sound card, or problems with drivers. If it is some other component in your system, then you need to find out which one it is. Monitors have high speed oscillators which can produce annoying high pitched squeals, particularly in the flyback transformer section. I have a television which does this intermittently. Some of the components (transformers in this case) begin vibrating at a very high frequency, you can easily identify the component by touching it (after first grounding yourself to the chassis to eliminate any static charge) with your finger, which stops the vibration.

Basically I would remove the lid, and get the system to start making this noise, and then by listening and touching the various components figure out where it is coming from. Then in most cases that part will have to be replaced, or maybe you can put some damping material such as insulated foam tape to dampen the vibrations.

I have actually heard processors generate these tones! Using a different (heavier) heat sink or removing and replacing the processor in the socket will usually correct it.  It could also be one of the fans in the system particularly the smaller ones used on processor heat sinks. If it is the fan, then the bearings are dry and you will want to replace it not only because of the noise, but because that noise indicates it will soon seize up.

9. Can you provide jumper settings for my K6 CPU?

Reader: I am having difficulty figuring out the jumper settings I should use for my K6 CPU. Your book only goes up to the K6-2 450 processor! Can you give me the proper settings?

Computer Doctor: The bus speeds and multiplier settings would be as follows for faster versions of this CPU: