PhilsComputerLab wrote:What is the reason for Panasonic caps not being recommended for VRM on P4 / Athlon 64? They don't make low ESR capacitors?
I have two AOpen P4 boards with Japanse capacitors. Interestingly they have a mix of brands. One has Panasonic and Rubycon, the other one Panasonic and KZE or something similar sounding.
Panasonic caps were often used on P4/Athlon 64 boards and later... And for that matter, Asus even used UESR caps on Athlon XP boards (Unfortunately they used Nichicon HM from a time when they were a defective series, so you always see them bloated. The A7N and A7V series are a good example of this). But the series used were FJ or FL... The problem with FJ and FL is that they were never sold directly to the public.
These days, you're limited to the diminishing supply of UESR caps from Nichicon, who stopped production last year or so. Technically, Sanyo/Suncon will still manufacture WG series, but I can't confirm that. It's either that, or you use Polymer caps like carlostex just mentioned.
You will have to drop the capacitance though, especially on the VRM high where you always need a 16V cap for the 12V input. So typically, for VRM high caps where there's space for only an 8mm part, you use something like 16V 270uF (whereas you'd use 16V 1000uF with an electrolytic). The way polymer cap technology works, you don't gain capacitance with height, so even taller 16V 8mm caps will not be much higher than 270uF. I think 470uF is the maximum at 16V in 8mm. For the VRM low, you can get 2.5V 1500uF caps in 8mm. 2.5V caps in the VRM low are always acceptable replacements for 6.3V parts because the CPU voltage will never go above 2 volts.
Having said that, the theory behind using polymer caps in these types of VRMs is that you lose nothing by halving the capacitance because lower ESR is more important.