[PD] about latency

[Alex]

Hi,

When I start up pd My version of portaudio tells me the latency I have: 
46ms
I have built a patch that records sound input on a tempo and I have 
noticed that my sound takes some times to get into pd. I have always 
thought that latency was the time the sound would put to get in then 
out but I thought that the sound would put something like 0.005ms to 
get in and a file played from the HD would put the same. So as I did 
not care about direct monitoring stuff, I did not mind.
Recently I have recorded samples on a tempo generated in pd and when 
playing the samples back I have noticed that my samples were not 
synchronized with the tempo. Can somebody confirm me that the signal 
get some significant time before getting into pd ? Or else ?
Also, I have then tried to play my samples a bit earlier than the tempo 
something like 89ms and then my samples where back on tempo. But 2 days 
later that 89ms became 130ms. (I used different patches) Can the 
in/output latency be variable according to the CPU I use ? Humm...

Alex