View Full Version : cpu voltages question?
02-28-2002, 07:38 PM
so i just got that 400watt PSU and the 12V+ is shooting up to about 13.245 when i run something that requires the video card.
is this bad?
and if you guys can, help me distinguish the difference between all those voltages...like the 12, 5, 1.8....
02-28-2002, 09:14 PM
Here is a quick breakdown of what all of the voltages coming from your power supply are used for:
The -5V is for Legacy ISA products, so you will probably never need to use this. The -12V is once again for Legacy ISA, but it is also for serial ports, including the PS/2 port. 3.3V is used for motherboard logic and for AGP and PCI slots. +5V is for motherboard logic (TTL), drive logic, and for PCI and ISA slots. +12V is for fans, hard and optical drive motors, and for PCI and ISA slots. The 1.8V that you see in your BIOS is the voltage that your CPU is receiving. As transistors get smaller and smaller, in general, less and less voltage is required for switching action. Therefore, today's CPUs run at lower voltages than CPUs of the past. Of course, when you consider that the number of transistors on today's chips outnumber older chips by millions of devices, the input voltage required may not represent an overall decrease.
The +12V rail generally has 5% regulation, which would mean that it should swing to about 12.6V. I am a bit suspicious about the 13.245V reading from your BIOS. While video cards may place a large load on the power supply at times, it is still on par with the load placed on the power supply by drive motors. I am one to never trust any readings displayed in my BIOS, be it voltages or temperatures. This is why I am building a circuit to monitor the temperature on my CPU directly, which will instantly shut down my power supply if the temperature gets too hot. :P
03-01-2002, 12:17 AM
thanx, that's actually helpful. i use my asus software that came with the mobo to monitor the system.
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