Increasing CPU usage of PostgreSQL

Hello All,

I am using jdbcrunner-1.2 to run PostgreSQL performance tests. For
certain tests, i need to increase the CPU usage of the servers
especially at user level.
I tried using both tpcc and tpcb load with scale factor of 100. Even
after setting the number of client connections as high as 420, I am
unable to achieve high CPU usage. It is hardly 3 percent. I think this
is because most of the client connections are idle.
The tpcc and tpcb transactions seem to be consuming very less CPU.

In postgresql.conf file, I have lowered checkpoint segments to 1 in
order to overwhelm the server with checkpoints but no significant
increase in iowait of the CPU.

Can somebody suggest a better idea to load PostgreSQL servers to
increase CPU usage.?

Configurations of my machine is:

Processors: Xeon E5-2650 Processor Kit
Intel® Xeon ® Processor E5-2650 (2 GHz, 8C/16T,
20 MB) * 2 nos

RAM : 32GB DDR3-1600 REG Memory Kit
8x 4GB Registered ECC DIMM, DDR3L-1600(PC3L-12800)

HDD: 450GB 10K Hot Plug 2.5-inch SAS HDD * 8 nos
1 x 450 GB SAS HDD, 2.5-inch, 6Gb/s

Disk Speed : 10,000 RPM

RAID Controller (512MB, RAID 0/1)

Thank you,