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Shooting for 504Mhz with Dual Heat-Sink
by Apex (16/9/98)

Shooting for 504:

Ok, you read all the hype about the celeronA processor and you ran posthaste to the store to pick one up. You were wise enough to pick up an Abit BH6 motherboard, knowing full well that it's the best all around and overclocking board available today. You run home and in no time, you're up to 450mhz or 464mhz at 2.1 volts or so and running strong. Unreal flies by at incredible framerates and your system is rock solid. You laugh thinking this would give a Pentium II 450 a run for it's money. You think to yourself that you paid is less than you would have for an iMac. You laugh some more...

But the speed bug is always nibbling at your toes, isn't it? Like some drug, "more" is never enough. Welcome to 504Mhz...

Ok, reality check here. First things first. The things here CAN AND MAY cause serious problems to your system. Mistakes can cause your brand spanking new CPU to become a $160 piece of postmodern art. Errors as simple as pouring silver alloy thermal grease all over your CPU/Motherboard can fry your computer, your hands, your house, the RX-7 in your garage, your little sister's overprocessed hair... You get the picture. AND, this is not guaranteed to allow you to run 504Mhz. If you are unlucky enough to get a processor cut from the margin of the wafer, you might be SOL. If some disgruntled Intel employee decided to scrape "Bill Sux" too deep on your L2 cache, this will not make it to 504Mhz. Know the risks. If you're willing to deal with them, read on:

Note: I will constantly refer to 504Mhz because I have a Celeron 300A chip that is locked at 4.5x multiplier. This means I'm running at a 112Mhz front side bus frequency. At this speed, my AGP is running at 75Mhz, 12mhz above spec. My PCI and IDE is running at 37Mhz, 4Mhz above spec. Your cards and hard drive may not be able to take this. Mine were able to. I'm using:

Intel I740 AGP card

Creative Dxr2 PCI DVD decoder

DCS S805 A3D PCI sound card

USR 56K Voice/Fax/Data ISA modem

IBM 10.1G Deskstar 14GXP 7200rpm 512k cache Ultra/DMA33 IDE hard drive

Creative 2X DVD-ROM

128Meg dimm of Micron -8C ram (same price as cheap ram, higher speed capacity. There is NO need to get expensive CAS 2 ram, such as Samsung -GH or equally expensive -G8, or even more costly -G7. Most quality CAS3 ram can reach 112mhz bus, though cheap ram and poorly constructed PCB's cannot).

If you have a Celeron 333 chip, slightly different principles apply. You are going to start by shooting for 500mhz (5x100). If you make it, go for 515, which is 5x multiplier and 103 (100mhz bus with turbo enabled). If you can do that, then shoot for 560Mhz (5x112). Overclocking the peripherals only applies in practicality to the 560Mhz level, which most likely is going to be difficult to reach.

With 1 good heatsink, I was able to reach 464Mhz (4.5x103) with my C300A at 2.05 volts. At 504Mhz, even at 2.2 volts, I was only able to barely get into windows, it would crash or freeze within a minute. After I did the second heatsink mod, I was able to run 504Mhz at 2.0 volts, ROCK STABLE. It is now 5 days later and no crashes, even through extensive heavy use.

Ok, with all that out of the way, here are the instructions on how to put together the dual heatsink rig. I'm going to cut this in 3 sections. The first section will outline the basic principles and things you have to check. The second is on your main heatsink choice. The third is going to cover putting the cooling system together.

SECTION 1 - Basic Principles & Things to Check

First thing to check is are you able to post at 504mhz with L2 on. If you could not post at all when system is cool (hasn't been running for at least 1/2 hour or so.), extra cooling WILL NOT HELP. Turn the voltage up a little if you can't post (ABSOLUTELY no more than to 2.3volts); see if that helps. Please please remember, if you can't at least post, extra cooling will do nothing for you. It will merely be a waste of time (though it'll probably make your processor last longer.

If you were able to at least post, but froze soon after that, then cooling may be your solution.

First off, look inside your case to make sure there's enough room for a second heatsink. There should be enough space, as long as your secondary heatsink is squat. Then, take the Celeron retention mechanism off of your motherboard. You will no longer be able to use that. But have no fear, as long as you don't play Frisbee with your computer, your processor will stay where it is.

Equipment Needed

1. 1 Main heatsink/fan - more details on this later

2. 1 Secondary heatsink/fan

3. 1 packet of NON-electrically conductive (IMPORTANT!!!) thermal grease, enough for 2 applications

4. 4 1" long Bolts and 4 nuts of corresponding sizes

5. Screwdriver and wrench

6. Thin, heat resistant electrical tape.

7. Scissors

8. Cold beverage of choice (for afterwards)

Possible Extra Equipment Needed

1. Steel wire

2. 4 springs that fit over the bolts

3. Electric drill with high speed (tungsten carbide is suggested) metal boring bits.

SECTION 2 - The Main Heatsink

Decide what main heatsink you are going to use. Many suggest the 2 fan one from Global Win or Computer Nerds. Those are both ok units. I would suggest if you're doing something as radical as dual heatsinks, mind as well go for a good main heatsink, right? The main heatsink still does most of the heat dissipation.

What I did was convert a good OEM P2 heatsink. Why did I use this? Most Celeron heatsinks are small, light, and use 15-20 rows of fins. As you can readily see, this is a poor design. The huge, heavy OEM P2 heatsink has 136 individual pins with a full 1" height. It has a much greater thermal capacity due to its mass as well as a much greater thermal dissipating capacity due to its pin instead of fin design. What you have to do is drill 4 holes in the heatsink, to match the mounting holes for the Celeron. Aluminum is reasonably soft, so it's not too difficult. Just make sure your alignment is good. Also make sure you don't drill the holes too "high" on the heatsink, or else the heatsink will sit too low on the processor and interfere with the plastic on the Slot-1. After drilling, get your two (hmm...you can use 3 if you want) fans and attach them to the face of the heatsink using steel wire. Make sure the wire is snug and no loose ends are sticking out where they can short something on the fan, CPU, motherboard, or nearby components.

Chances are, you're not going to have enough fan connectors on your motherboard (this is given you are using 2 fans on your front heatsink, 1 on the back heatsink). For one of the front ones, rip the 3pin connector off. Then, strip the wires up about 1.25cm. Fold that 1.25cm bare wire in half and twist so it looks neat. Then, shove each wire into the back of the other 3 pin connector from the front fan. It will fit pretty well, and tension will hold it in. After you're done with this, it will look like a 3 pin connector with 6 wires coming out of it, 2 in each pin. Use some of your electrical tape to bundle the wires together close to the 3 pin connector, to make doubly sure that they won't come out. Your 3 CPU fans are now using two 3 pin connectors, perfect for the BH6 motherboard.

SECTION 3 - Putting it all Together

Get out your electrical tape. I used thin clear high temperature 3M electrical tape. Stay away from that thick black stuff that turns to goo when heated up. If it is too thick, your heatsink won't be touching the back of the PCB at all. Completely cover the BACKSIDE of the CPU with tape, except for the small square where the processor itself sits. Do a clean job. You'll be happy you did.

Clean off your heatsinks. Carefully scrape off the graphite pad/thermal tape. Use the thermal grease instead. Apply a THIN EVEN patch of thermal grease onto the square of PCB where the CPU sits, where it is untaped. On the other side, apply a THIN EVEN patch of thermal grease on the metal plate of the CPU. Carefully align both heatsinks (the bigger/better one goes on the front side, of course) and place them on the Celeron. It will look like a "sandwich" heatsink/Celeron/heatsink, with fans on the outsides. Then, take 4 bolts and put them through the mounting holes, starting from the main heatsink side. You now have the heatsink/Celeron/heatsink with the bolts in place, sticking out the backside. Take the 4 springs, and place them on the bolts and then place the 4 nuts on the bolts. SLOWLY, CAREFULLY, and EVENLY tighten them down. You want it so that it won't wiggle, but not too tight. If you tighten too much, you will crush your processor. Just tighten so it stays firm. Make sure all 4 corners are even, so the heatsinks rest flat against the CPU. The springs are not completely necessary, but are good for safety, and to keep the unit together in the face of expansion and contraction due to thermal cycling (hot, cold, hot, cold).

Plug in the fans, plug in the Celeron, and turn on your computer. Start at 66mhz bus, just to see if everything is working properly. Look inside the case. Are the fans all running ok? If the computer doesn't boot up, don't worry, you didn't seat the CPU in properly. Even a slight misalignment causes this. Turn it off and reseat the CPU. This took me 2 tries.

Ok, moment of truth. Reset the computer and change to 100mhz bus. Start at 2.0 volts. If it is still unstable, move slowly upwards, starting at 2.05, then 2.1, then 2.2.

When you reach stability, play some of your 3D games to double check. By all means, keep the computer on and running hard for about 2 days so the system can burn in. After this time, sometimes you can lower the voltage down a notch and still have it be stable. The "burning in" process tends to do that with electronics.

Sit back, play with your new 504Mhz toy, and go enjoy that cool beverage. The first Intel processor to come out at 500mhz is sure to cost at least $900. You just bought one with $170 or so and some of your time.

SECTION 4 - Photo Shots

Fig 1 : This is the first picture of the back of the cpu, sorry it's fuzzy.  My camera sucks.  It's a flat heatsink w/ 5mm high pins, and a single fan.  Notice how it is attached using 4 screws.  You can see the full sized heatsink on the other side.

Fig 2 : Above is a picture of how the Radio Shack DC Blower motor is attached.  The mouth opening is flush with the plastic 5.25" panel. Notice the red wire goes to the yellow, and the black to the black.

Fig 3 : This is a picture of the front heatsink, with 2 fans, attached to the cpu.  Notice the bolts and nuts.  Also notice that both fans are connected to the same 3pin connector.

Fig 4 : Above is a picture of the front of my case.  The Radio Shack Blower is at the top 5.25" slot and is sucking hot air out from the top of the case.  Near the bottom, you can see where the I widened the tiny ventilation holes behind which a 80mm fan is drawing in cold air.

Fig 5 : This is a picture of the inside of the case, near the CPU.  Though it is a little hard to see, notice how the rear heatsink is still about 1" from the back of the case, giving room for air to move.  Behind the CPU is 2 60mm case fans.  The top one is sucking air out, and the bottom is blowing air in.   After a little experimentation, this seemed to work best.

Fig 6 : Here's a picture of the rear of the case.  You can see the two fans behind where the CPU resides.  The powersupply fan is reversed, so it's sucking hot air out.

Fig 7 : Here's a picture from the open side of the case.   Fans are labeled:

1. 60mm high output fan sucking hot air out

2. 60mm fan blowing air in

3. 50mm heatsink fan blowing air towards back heatsink

4. 50mm heatsink fan blowing air towards main heatsink

5. 50mm heatsink fan also blowing air towards main heatsink

6. 80mm case fan blowing air towards 7200rpm hard drive

7. 80mm case fan sucking cold air in near bottom of case

8. Radio Shack DC Blower motor sucking hot air out of case

9. 80mm power supply fan turned around to suck hot air out

10. 40mm fan on i740 card.

Fig 8 : Here's a picture of the backside of another Celeron that I taped.  Notice the tape covers the whole backside except for the center where the CPU itself resides.  The tape even covers over the CPU to PCB pins.