OPC communication between plc and pc slow

I have an opc communication between a pc (with a common network card) and a plc S7 315 2 dp, but it is extremely slow, what point should I pay attention to to speed this up?
Thanks.

Please describe the EXACT hardware and software setup on both PC and PLC.
How much data ?
How often ?
What is "slow" ?

JesperMP said:

Please describe the EXACT hardware and software setup on both PC and PLC.
How much data ?
How often ?
What is "slow" ?

Click to expand...

Plc_side : cpu 315-2dp 2AG10 v 2.6.5 ethernet card lean, cpu-cycle time = 50 ms, cpu load for communication : 50%, , pc-side : standard network card and Simatic net 2008. About 6 reals, 4 dint's, 6 bools are written within 6 seconds. These are 'separate' variables = not placed in an array. The values are written with the write synchronously method by a Delphi programm, but same delays are encountered by the OPC-scout.
To the mpi port also an TP177A is connected, to the ethernet card also a MP277 card is attached. If the MP is connected to the ethernet or the mpi does not make difference. When the MP is disconnected communication goes gast : 1-2 seconds. The panel has a lot of variables, but only few are updated continiously.