I have a dual core processor

[Klammy]

Every time I turn on multicore rendering on in TF2 or L4D my game lags more than it did before, any ideas/suggestions?

My processor; AMD Athlon? 64 X2 Dual-Core

 

[Clarko]

I had a similar issue and found it was due to 1. The current drivers I was using ( which were the up to date) so I reverted back to some more stable ones 2. I have Rainmeter and Rainlander as my desktop toys for productivity which I learned also cause the problem so I shut them down before I start the game. Even steam sometimes but I didn't exactly get lag it was more of a quick skip which I can notice right again and I did not like. The funny thing was that my FPS was always 80-120 and never dropped so it was a weird glitch. Hope it helps.