Postgresql on an AMD64 machine

I'm not sure if this is the appropriate list to post this question to
but i'm starting with this one because it is related to the performance
of Postgresql server. I have a Penguin Computing dual AMD 64 bit
opteron machine with 8 Gigs of memory. In my attempt to increase the
number of shared_buffers from the default to 65000 i was running into a
semget error when trying to start Postgresql. After reading the
documentation I adjusted the semaphore settings in the kernel to allow
Postgresql to start successfully. With this configuration running if I
do a ipcs -u i get the following.

------ Shared Memory Status --------
segments allocated 1
pages allocated 30728
pages resident 30626
pages swapped 0
Swap performance: 0 attempts 0 successes

------ Semaphore Status --------
used arrays = 1880
allocated semaphores = 31928

------ Messages: Status --------
allocated queues = 0
used headers = 0
used space = 0 bytes

I'm questioning the number of semaphores being used. In order for
postgresql to start I had to set the maximum number of semaphores system
wide to 6000000. This seems to be an abnormal amount of semaphores. I'm
curious if this is a bug in the amd64 postgresql port. Is anyone else
using postgresql on an AMD64 machine without similar issues?

TIA
Mark