I also suffer from random lag-spikes during gameplay. My setup:
- No other software running on the background (except Avast antivirus)
- Windows 7 64bit installed ~month ago.
- 6 GB DDR3 memory
- Quad-core Intel from 2009
- Nvidia GTX 260 with newest drivers installed
- Osu! & Windows 7 running from SSD harddrive
- Osu! is in fullscreen, using DirectX. Resolution 1280x960. FPS limited to 120.
- Osu! is upgraded to the newest version. Can't remember if i had lag spikes with previous versions...
Lag-spikes are very random, and pretty rare. I would say that one spike every 1-2 hours.
During the lag-spike music plays normally but graphics freeze for <1 second. In fast paced maps it usually causes failing of the beatmap.