Extreme lag/game freeze on snapshot with HD texturepack

It seems snapshot 13w04a has a performance issue with HD texturepacks when Minecraft 1.4 didn't have any on same computer (but Minecraft 1.4 had more glitches and less features than 13w04a of course).

What happens is (in order):

• Smooth framerate during ~30 seconds

• Horribly laggy framerate during ~20 seconds (impossible to play)

• Smooth framerate during ~30 seconds

• etc...

The problem happens with a 128x up-to-date texturepack (optimized for 13w04a). However, the problem also happens with default texturepack but is less noticeable (it's just like a lag spikes).

The game doesn't crash so there is no crash-report.

Note:

• My LWJGL library is up-to-date.

• My computer (a dual-core one) has a good hardware and is able to run MassEffect3 without any problem.

• The problem is less noticeable (or shorter) when using a lower resolution of texturepack

• When the problem happens ingame, it also still happens in the main menu before stopping

• During the problem, one core is at 100% but the other is iddle.

• Can be related to MC-4349, MC-2098, MC-1514, MC-3130, MC-8304, MC-2176 and MC-2434