unstable server fps

[paradisha]

Hello,
I have dedicated machine. Server specification is
CPU: Intel Core 2 Quad Q8200
RAM: 4GB DDR2
Motherboard: Intel DG31PR
LAN: Intel PRO 100/S Desktop Adapter
OS: Windows Server 2003 x64 Standard
ISP: Korea Telecom FTTH

Server startup command: srcds.exe /high -console -game tf +map cp_orange_x3-3 +maxplayers 32 +fps_max 600 -port 27018
Server cfg:
fps_max 600
sv_minrate 20000
sv_maxrate 100000
sv_minupdaterate 20
sv_maxupdaterate 50
sv_maxcmdrate 50
sv_mincmdrate 30

It runs 3x TF2 (32 Slots + 16 Slots + 16 Slots) Servers. But it have problems.


As you can see, fps is very unstable. Join the server, and checking server fps use net_graph 4, it reaches 500, 64, 500, 64, 500, 64...

Is there anyway to stablize server fps?


Here is cpu load graph.