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Advanced PCB Course: Thru-hole vias versus microvia for connecting CPU to DDR3

mstamler , 10-20-2022, 11:33 PM

In Lesson 2 for "Advanced PCB Layout" you talk about using microvia and thruhole vias to connect data banks from the CPU to the four DDR chips. At 1:47 of the video you start your discussion by noting that some banks at the CPU using thruhole and some use microvias. You then say that you need to swap data banks to make the thruhole vias consistent with data banks at the bottom.

All this is good. What I don't understand is how you reached the decision to put thru-hole or microvias in the various data banks at the CPU to begin with?? This you don't discuss. Can you clarify this?

Wouldn't it be more prudent to first decide which data bank will go to which DDR chip, top or bottom, and then use the appropriate via, thru-hole or microvia, to achieve optimal routing?

robertferanec , 10-24-2022, 02:56 AM
I started from the middle - address command control and then I knew what vias I have to use for closest data banks to the addr/cmd/ctl so I can fit it all.
mstamler , 10-24-2022, 11:44 PM
But you still needed to perform bank swapping to get it right!!
robertferanec , 10-26-2022, 08:35 AM
If it's needed, yes, you may want to do bank swapping. You would like to have the banks ordered the way it will nicely connect in PCB layout - it will make the layout easier.
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