Mupen64 never was a performance monster, even in Windows versions. Although, it was the most "portable" N64 emulator. Project64 is absolutely x86 oriented, and 1964 was a complete mess...1964 0.7.3, especially, was fast as hell. But instable as hell + 1.

So, we have specific problems with Mupen64 binary and with gln64. I believe - knowing N64 emulation history - that the binary problems are worst. So, binary updates are mandatory. "Simply" problems, when resolved, give huge performance boosts.