Why is pgbench suddenly slow?

Hello all:

I know this is a hard question to answer, but I'm seeing some behavior
that's very odd. I have a postgresql application, with a PHP interface,
running on a single server (PowerMac G4 with 512 meg of RAM and a relatively
old version of LinuxPPC). Withno one on the system, my pgbench results vary
between 70-100 tps.

I just set up a big brand new server, tons of RAM, 15KRPM drive, two
processors, the works. Then I decided to run pgbench to see how much speed
I'd gained. The result? A consistent 30-33 tps, though it scaled very well
and stayed right at that level across loads from 1 to 64 connections.

What on earth could be going on? The new server has 2G of ram and I set
aside about 512 meg for shared memory.

Any ideas?

- steve