Emulator

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Game Name?
All games seem to be affected.

Game ID?
See above.

What's the problem? Describe what went wrong in few words.
When XFB is set to Disable, I experience a significant drop in performance, for example:

Super Smash Bros. Melee v1.02 (Main Menu)

4.0-7084 - 170 FPS
4.0-7088 - 42 FPS

A similar problem also happens with both SpongeBob SquarePants: Battle for Bikini Bottom and The SpongeBob SquarePants Movie. For the start screen of BFBB, the game hovers around 40FPS, non-fullspeed. However, in game, the game stays at 30FPS with 100% emulation speed (the same happens in TSSM), when it should be at 60FPS.

Shouldn't we just get rid of Disabled XFB if it:

1) Causes problems in many games e.g. Capcom vs. SNK 2 EO
2) Provides little to no performance improvement over Virtual XFB?

What did you expect to happen instead?
I expected performance with Disabled XFB to be equal to or higher than that of Virtual XFB.

What steps will reproduce the problem?
[Don't assume we have ever played the game and know any level names. Be as
specific as possible.]
(For Disabled XFB issue)

1. Start any game
2. Set XFB to 'Disable'
3. If your PC still runs the game at full-speed, try running the game with Disabled XFB and frame-limiting off, then with Virtual XFB and frame-limiting off. You should see a significant difference in performance.

Dolphin 3.5 and 3.5-367 are old versions of Dolphin that have
known issues and bugs, so don't report issues about them and test the
latest Dolphin version first.
Which versions of Dolphin did you test on?
4.0-7099
4.0-7088
4.0-7084
4.0-7015

Does using an older version of Dolphin solve your issue? If yes, which
versions of Dolphin used to work?
4.0-7084 and older.

What are your PC specifications? (including, but not limited to: Operating
System, CPU and GPU)

Athlon X4 750K @ 4.1GHz
AMD Radeon HD 7770
Windows 8.1 x64