1
\$\begingroup\$

There are multiple traces connecting the gpu to the pcie slot to communicate with motherboard. On some traces, which I suspect to be Motherboard to GPU, there are 220nf caps. Normally I would expect some decoupling caps to filter the signal, that would connect to trace on one side and to GND on the other. Are these there so only the ac (the signal) can pass through?

enter image description here

\$\endgroup\$
5
\$\begingroup\$

Yes, those are AC coupling capacitors. The PCIe specification requires the lanes to be AC coupled with a 220nF capacitor.

\$\endgroup\$
1
  • 2
    \$\begingroup\$ The capacitance is actually a range which has changed across the generations of PCIe. 220nF is a good compromise that works for gen 1, 2 and 3. \$\endgroup\$ – Peter Smith Feb 27 at 10:25
0
\$\begingroup\$

If they are in series with the signal (and they appear to be) then you are correct. 220nF seems rather large for that purpose though.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.