Better Late Than Never …
I’ve got to admit it, this article is rather late. Tom’s Hardware has the knowledge of how to change the core clock of an Athlon-processor since this new and powerful AMD-CPU was released. As you might remember from the first Athlon-Overclocking article, there is a tough way to change the clock speed of Athlon and there’s a much easier way as well. I decided to describe the tough way first, so that AMD wouldn’t get mad at me and so that AMD’s business wouldn’t get damaged even more than it is by the ridiculous, but currently improving, Athlon-motherboard situation. Altering Athlon’s core speed by soldering and de-soldering several SMD-resistors on Athlon’s, normally covered, PCB is a difficult job and thus only very few people have tried it. Back in the article, where I described this procedure, I told you about an easier way of overclocking Athlon and promised to finally disclose the details of it. Now I can see that it really is about time to fulfil my promise, because several publications popped up in the last few days using either home made or semi-home made hardware for Athlon-overclocking.
Overclock Using the Internal Connector of Athlon
Most of you know it, Athlon’s clock speed can be altered via its internal 40-pin connector.
You will have to open Athlon’s case to get to the internal connector. Opening the CPU-cartridge is done by C_A_R_E_F_U_L_L_Y preying the plastic cover from the aluminum heat plate. It’s best to use a knife with a large and very sturdy blade. Be careful that you don’t destroy any of the parts inside the cartridge! The plastic cover is connected to the heat plate with four little metal pins that stick inside little notches inside the cover. It’s very similar to opening an old Pentium II processor cartridge. Three of the pins come off very easily; the fourth is a tough one. In Athlon’s case the tough pin is in the lower left corner when you look at Athlon’s plastic cover so that you can read ‘AMD Athlon Processor’. It’s the opposite side to where you find the black plastic ‘AMD’-insignia.
The Parts Required for the Overclocking Card
The most professional plug for this connector looks pretty much like this:
It connects directly to a little PCB required for the dipswitches and resistors that you will need. So far, all solutions that I have seen on the web were rather unprofessional. If you want to go for it then either get a plug like this (AMP is the manufacturer of the above one), or only buy an overclocking-card that’s build like this. Other solutions may require a lot of little wires, which is messy and can be dangerous if one of those wires breaks. Using a connector that doesn’t ‘go around the corner’ as this one will make the PCB hovering very clumsy above the CPU.
The next thing you need is the circuit-diagram.
You can see that the circuitry is rather simple, however there’s one little problem. You require +5V, GND and +3.3 V as well if you want to do it right, following the spec. This surprised me as much as it may surprise you and we are trying to find out if VCC_CORE could be a viable alternative as well. However, VCC_CORE (supplied from Pins A8, A12 and A15 of the connector and used for the BP_FIDs) is a lot lower than 5 or even 3.3 V. Anyway, please realize that the pull-up resistors are of major importance. They ‘disable’ the selection on Athlon’s PCB (the resistors that I described in my initial Athlon OC-article). You could possibly do without the pull-ups and the external voltages if you’d remove all the VID and FID-resistors on Athlon’s PCB. I suggest that the only solution for this problem is a ‘CPU-external’ voltage-supply, using a normal power-chord, just as the ones used for everything inside the computer, e.g. for fans, hard-drives and more. Those chords supply +5 V, +12 V and GND. You grab the +5V and GND from it and use a tiny little voltage-regulator chip that produces the +3.3V. This little chip does not need to have any major power-dissipation (up to 400 mW). The 3.3 V are only required for some pull-up resistors as you can see in the above diagram. You might also see a problem in the lower part of the diagram, the one for the BP-FIDs. Of course you don’t require switches that can switch between two different sources, two on/off-switches can do the same job. You only have to remember to keep the two switches in alternating = opposite conditions, on/off or off/on.
Summarizing the requirements gets us to the following list:
- An AMP-connector 40-pin, pitch 1.27 mm or 1/20 inch
- A PCB which you design according to the above diagram plus the area of the 3.3 V voltage-regulator
- Two 8-switch dipswitches
- Four 4 x 56 Ohm SMD-resistor clusters
- A low wattage SMD 3.3 V voltage-regulator
- A PC-power supply Y-cable (supplies wires and connector for the power supply of the card)
With those parts you can build your own universally usable Athlon overclocking-card. I know that many of you won’t be able to design their own PCB, but I am sure that shortly after the publication of this article, many companies will start building their own overclocking-cards. With the information taken from the circuitry that I published, the offered cards will hopefully be more professional than what’s currently out there.
Let’s get to the settings
The first table shows the ‘FID’ = frequency ID settings, more commonly known as the ‘multiplier-settings’.
The next table is called ‘BP_FID’. You need to adjust those settings too if you want your Athlon to work at the desired frequency you adjusted in the ‘FID’-section. Please make sure to choose the same settings for the ‘BP_FID’ as you chose for the ‘FID’.
Last but not least there is the table for the voltage selection. Please be reminded that increasing the voltage can damage your CPU and don’t forget to re-read the comments I made in the first Athlon-overclock article.
The Second Level Cache Divider
On the web is a lot hoopla going on about Athlon’s L2-cache divider. The Athlons that are currently available are all using a divider of 2, which means that Athlon’s L2-cache is running at half the core-clock. Upcoming models that run at 750+ MHz will use dividers of 2.5 and 3 until AMD has integrated Athlon’s L2-cache on the die. There’s several websites that tell you to change the SMD-resistors on Athlon’s PCB to change the L2-cache divider. Tom’s Hardware knows that this is not necessary. The L2-cache divider can actually be changed via a software setting. It’s usually the BIOS of the Athlon-motherboards that sets the divider and the BIOS is designed that it automatically changes the divider for higher clock-frequencies of Athlon. Thus you normally don’t need to mess around with those settings when you plug an Athlon overclocked to 800 MHz into your board, the divider will automatically be changed by the BIOS.
Unfortunately we don’t know the software settings for the L2-cache divider yet, but we are working on it. Until then, I’d still like to advice against messing around on the PCB unless you really feel that you have to.
Epilogue
We are currently working on a PCB-layout that we will publish as soon as possible and some other workaround that might not even require a complete OC-card. This will also be published as soon as we could make sure that it works.
Please excuse that I wrote this article in a way that clearly addresses people who know how to work with electronic circuits. I am aware of the fact that most of you won’t be able to do this operation. However, I only want to get the word out on how to make a proper OC-card to every company that feels able to produce it. This way there will soon be a lot of overclocking-cards available for each of you and you don’t need to do any soldering operation by yourself anymore.
Addition [Updated]
The 56 Ohm FID Pull-Ups
AMD’s original design has one flaw, which made me re-check my circuitry-diagram several times before I released it on Saturday. The pull-ups for the FID-selectors are with only 56 Ohm against a voltage of 5V very low, resulting in a hefty power dissipation of 440 mW for each of the four resistors when the FID-dipswitch is in ‘ON’-position. This results in an unnecessary heat-production of the device and most likely in a short life span of the resistors. The pull-ups have to work against pull-down resistors of 1000 Ohm on the Athlon-PCB, so that 220 Ohm should suffice just as well. At this resistance each SMD-resistor would only have to ‘burn’ 113 mW, which should not result in any excess heat production.
Creating a Source for 3.3 V Out of the 5 V supply
Brian Andersen sent me a good idea to ‘circumvent’ the voltage-regulator to produce the 3.3 V out of the 5 V power supply. He suggests to use three 1N4001 diodes in series. The voltage drop across each diode is about 0.6 V, so that you would reach 3.2 V, which would be close enough to the needed 3.3 V. Thanks Brian!
