- Date:
- Monday , July 10, 2000
- Author:
- Kyle Bennett
- Google +1
Get MORE POWER on your Mainboard
By: Ed Gannaway
As all the regular readers of the HardOCP know, the Celeron II has become one of the darlings of the overclocking crowd. With a price hovering around the $110 mark for the 533 iteration and the ability to run (in most instances) at over 800 MHz it’s no wonder this chip is so popular. However, in combination with some motherboards these lofty goals are not attainable. At times the problem rests with the chip but oft times it is due to the options available on certain motherboards. This is where the adventure begins.
Editor's Note: To make this happen you will need a Celeron-II system with a mainboard that has adjustable voltage for the CPU.
Based on Kyle’s favorable review of the SOYO 7VCA a while back, I bought one to play around with. I coupled this with a Celeron II 533. As mentioned in the review, the 7VCA bios voltage tweaks only go up to +10% which for this chip means the voltage maxes out at 1.65 volts. Even at this, my dear little Celeron would not run stable at 800 MHz. I feared I was in possession of a "little cpu that couldn't." Since I also have an ABIT BM6, I plugged the belligerent chip into it and went straight for 1.8 volts. While in the BM6 it ran stable for over an hour while playing Q3. This left me in somewhat of a quandary. I could use the BM6 and miss out on all that ATA66 luvin', wait for SOYO to correct the problem (not likely), or I could take matters into my own hands, which is exactly what I did.
After reading the Intel spec sheet (http://developer.intel.com/design/celeron/datashts/) on the different pinouts I came upon the logic table (excerpt below) that determines at what voltage the CPU natively uses. These pins (and locations) are the VID0 (AL35), VID1 (AM36), VID2 (AL37), and VID3 (AJ37).
VID3 | VID2 | VID1 | VID0 | VccCORE |
1 | 0 | 1 | 1 | 1.50 (Default) |
1 | 0 | 1 | 0 | 1.55 |
1 | 0 | 0 | 1 | 1.60 |
1 | 0 | 0 | 0 | 1.65 |
0 | 1 | 1 | 1 | 1.70 |
0 | 1 | 1 | 0 | 1.75 |
0 | 1 | 0 | 1 | 1.80 |
0 | 1 | 0 | 0 | 1.85 |
0 | 0 | 1 | 1 | 1.90 |
0 | 0 | 1 | 0 | 1.95 |
0 | 0 | 0 | 1 | 2.00 |
0 | 0 | 0 | 0 | 2.05 |
1 | 1 | 1 | 1 | No Core |
NOTES:
1. 0 = Processor pin connected to VSS.
2. 1 = Open on processor.
The logic table shows the state of these pins from 1.3 volts all the way up to 2.05 volts; the Celeron II is factory set for 1.5 volts. This corresponds to only VID2 being internally connected to Vss (AK36). Different combinations cause the motherboard to supply different voltages.
Now here's the beauty of the whole thing - connect VID1 and VID0 (in addition to the already internally connected VID2) to Vss to make the CPU boot at 1.65 volts! This doesn't change the 10% adjustment factor in the bios, but now it STARTS at 1.65 instead of 1.5 volts! At 10% maximum tweak, the CPU now feasts on 1.8 volts of overclocking goodness whereas before the maximum was 1.65 volts...what used to be the max is now the default.
To accomplish this, I thought about soldering jumper wires across the back of the socket370. Not only would this make the change semi-permanent but also it would void the warranty. To solve this problem, I pulled one strand out of an 18 gauge multistranded wire and, using just a couple of turns on each pin, wire wrapped VID0, VID1, and Vss together on the cpu itself (see picture below) being extremely careful not to contact any of the other pins. The benefits of this option are:
1. Only the CPU is changed.
2. The CPU retains the new preset voltage regardless of motherboard used.
3. The motherboard warranty remains intact and I can swap out the CPU with a PIII without having to remember I had modified the motherboard.
4. It is reversible in about three seconds.
The end result is that my 7VCA will now run my Celeron II at 800 MHz (haven't tried higher yet...still having fun with it the way it is) rock solid stable!
VID1
VID2
VID3
VID0
Vss
Why not go higher, you might ask? Once again refer to the chart. As you can see up top, the internal VID2 connection (highlighted in yellow) is shared in the ranges of 1.5 to 1.65 volts and 1.90 to 2.05 volts. Without some kick-ass cooling, the upper range is probably out of reach unless you like the taste of Celeron popcorn! Anything between 1.70 and 1.85 volts requires VID2 to be disconnected from Vss. I would venture to say that it is impossible to disconnect this pin internally without destroying the whole thing therefore some external method would be needed. I don’t currently know of a reliable (heavy emphasis on reliable) way to insulate a pin on the socket format CPUs. You could cut the VID2 pin off of the CPU (bad idea!) or disassemble the socket370 on the motherboard and desolder the corresponding pin. The first method is permanent while the latter is reversible but requires more than just basic soldering skills. Perhaps someone more enterprising than I will find an easier method but for now 1.65 volts at default is the practical limit.