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#1
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Lower VCORE on A7V8X?
Hi
I have an ASUS A7V8X motherboard and I have recently bought a CPU Athlon XP-2400 Mobile 35 W. I want to run a cool and quiet PC (not overclocking) and therefore I want to lower VCORE as much as possible. This CPU needs a VCORE on only 1.35 V. When I test this CPU on my A7V8X I realized unfortunately that the lowest Vcore I can set is 1.525V. Is there an easy way to lower VCORE further? I have upgraded BIOS to the latest 1013. I saw in this newsgroup some months ago how you can increase VCORE with a resistor between pin 9 on L6917BD and ground. Can I just do the opposite and connect a resistor between pin 9 and Vcc (12V)? I want to have a possibility in BIOS to change between 1.2V and 1.4V. I wonder now if anyone has tested this approach and if so, the value on the resistor you have chosen. I would be very grateful if anyone has some thoughts about this subject. Thanks, Lars J |
#2
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In article , "LarsJ"
wrote: Hi I have an ASUS A7V8X motherboard and I have recently bought a CPU Athlon XP-2400 Mobile 35 W. I want to run a cool and quiet PC (not overclocking) and therefore I want to lower VCORE as much as possible. This CPU needs a VCORE on only 1.35 V. When I test this CPU on my A7V8X I realized unfortunately that the lowest Vcore I can set is 1.525V. Is there an easy way to lower VCORE further? I have upgraded BIOS to the latest 1013. I saw in this newsgroup some months ago how you can increase VCORE with a resistor between pin 9 on L6917BD and ground. Can I just do the opposite and connect a resistor between pin 9 and Vcc (12V)? I want to have a possibility in BIOS to change between 1.2V and 1.4V. I wonder now if anyone has tested this approach and if so, the value on the resistor you have chosen. I would be very grateful if anyone has some thoughts about this subject. Thanks, Lars J I see a couple of possibilities. The solution requiring the least knowledge, is to pry the five VID signals on the Vcore regulator chip, then control them with a five position dipswitch connected to GND. Prying the pins up is necessary to isolate any GPIO signals that the BIOS is using to drive those pins. (Use solder wick to remove the solder, and carefully pry the pin up a fraction of an inch with a dental pick, while heating with the soldering iron to free it. Too much prying will snap the pin off, or rip the copper foil, so be careful). If the BIOS has an option to modify the VID voltage, then there have to be some GPIO pins connected to the VID lines, to force them, and you don't want to damage those signals if possible. If you want to take the analog modder route, then a resistor connected to a regulated rail voltage higher than the output voltage should work. The +12V on a power supply will wander around a good deal (+/- 5%), while some voltages regulated by the motherboard will be much more stable. Your wiring must be kept short, to keep the wire from becoming an antenna. And, somehow, you'll need to figure out just how much resistance is required. (Search some of the private forums, to see if someone has already figured this out.) The thing that makes me nervous about the analog mod route, is adding the resistor could be affecting the stability of the control loop. If you can find instructions on a private forum of someone who has succeeded at undervolting this board, that is probably better than me guessing at whether it is going to work properly or not :-) If you plan on using a potentiometer to dial the resistance, remember that dialling the device to zero ohms could destroy something on the motherboard. There should always be a limiting resistor in series, to provide a measure of safety. So, the first part of your mission, is to find a locally regulated voltage on the board, like the +2.5 used for the DIMM or a local +3.3V if there is one. (By using 3.3V, the resistor value used for the voltage boost should be in the same ballpark as the resistor value needed to cause the output voltage to drop, so that is another advantage of a lower voltage like that. The resistor value would be a lot higher, if you are connecting to +12V or the like. Like (12V-Vout)/Vout times higher. Evaluating that equation for (3.3V-1.65V)/1.65V gives a factor of 1X compared to the "resistor value to GND" mod.) For that amount of messing around, I think the digital approach is less trouble. Practice your soldering skills on something else first. I have a lot of soldering experience with more robust boards, and I found the Asus board I worked on, to use thinner copper foil than I am used to. Delamination of the foil is pretty easy to do. And those tiny pins cannot be bent through too large an arc, before they snap off. Enough clearance to slide some mylar film under the pin as an insulator, is all that is needed. An Uber-style BIOS would be another way to get there. If someone has freed up some settings with MODBIN or the like, then a modified BIOS might open up more options. The A7N8X BIOS has been hacked, but I don't know if the A7V8X has been blessed this way or not. HTH, Paul |
#3
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Hi
I want to thank you for your answer and your valuable advices. I think I am going to do the digital mod which feels safest. Now I am going to practice to solder on an old, not functioning motherboard to increase my skill on SMD components. I hope I can report in this thread about a successful mod in the coming week. Thanks, Lars J |
#4
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Hi
I have now modded and tested the motherboard and I am very satisfied with the result. I now have VCORE =1.25V and the CPU runs very cold at 1.6GHz. The computer is also very stable and I have not have a single blue-screen or hanging. The modding was rather difficult because of the small sizes of components and wires but with patience and steady hands I succeded. /Lars J |
#5
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In article , "LarsJ"
wrote: Hi I have now modded and tested the motherboard and I am very satisfied with the result. I now have VCORE =1.25V and the CPU runs very cold at 1.6GHz. The computer is also very stable and I have not have a single blue-screen or hanging. The modding was rather difficult because of the small sizes of components and wires but with patience and steady hands I succeded. /Lars J Did you have any trouble getting the pins free of the board ? And, did you use switches, or just hardwire the five VID pins to GND or open, as appropriate ? Also, does this allow using less fan on the CPU ? Congratulations, Paul |
#6
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=|[ LarsJ's ]|= wrote:
Hi I have now modded and tested the motherboard and I am very satisfied with the result. I now have VCORE =1.25V and the CPU runs very cold at 1.6GHz. The computer is also very stable and I have not have a single blue-screen or hanging. The modding was rather difficult because of the small sizes of components and wires but with patience and steady hands I succeded. /Lars J Wow, Id love to do this with my A7v8x-x but it does sound tricky. -- ' gathering moss, android |
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