Originally Posted by
fastyÂ
I use those sort of capacitors for work - but I'm not going to bother fitting any to my Z77X-UD5H just yet
For those who are interested:
It is usually "good practice" to put capacitors like this on power supply signals to chips, especially processors.
Processors don't consume current smoothly; it tends to be drawn in gulps and spikes, with these "current transients" moving up and down incredibly fast. Now, when there's a brief high peak of current, the voltage at the chip will tend to drop a bit because of the electrical resistance in the circuit tracks. As the current falls, the voltage will rise. Not a good idea.
In principle, the "load line compensation" is designed to compensate for this fluctuation in current and keep the voltage actually at the chip steady, but in practice it can never react fast enough to keep pace with the very fastest changes of current.
Are you with me so far? Good.
So, this is where capacitors are useful. Think of them like little reserve buckets of current right at the chip, ready to supplement the power supply and provide the extra little transients of current when they are needed, smoothing out the current changes, and helping the load line compensation to cope.
I believe that the intel processor chips themselves actually have some capacitors integrated into the chip package. This is great, because that's exactly where they are most effective. Of course, more fitted on the board close to the processor should not do any harm.
Now, if you've got a really clever power supply on the motherboard than can react very quickly to the changes in current, the "belt and braces" capacitors fitted to the motherboard are probably less important. The digital power supplies that Gigabyte are using should have a very fast response to transient current changes ("transient load regulation"), so may well not need the extra capacitors. The fact that there are circuit board "pads" in place where capacitors could be fitted shows that Gigabyte considered the possibility of them being needed, but ulimately decided not to fit them. The cost saving is not much, so that's probably not the reason.
The heavyweight copper used by Gigabyte for their circuit board also reduces the droop in voltage with current transients, again making the extra capacitors less important.
Summary: Gigabyte are using a state-of-the-art onboard power supply. If the motherboard works well without dozens of extra capacitors by the processor, then leaving them out should only make it more reliable. A less experienced designer might fit them anyway "just in case".
