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a) Instead of the real random number generator, use a LFSR-based PRNG, with a polynomial that happens to give a good spectrum for acoustic testing with OLPC speakers. In addition to working around a unit- dependent problem with the MMP3's hardware RNG, this also speeds up the test because the LFSR is faster than the hardware RNG. b) Store 16-bit "random" values in the audio buffer instead of using 32-bit random numbers and hoping that the top and bottom halves are uncorrelated. This seems to give better decorrelation of left and right signals. c) Hard-reset the audio subsystem by powering off/on the audio island between the acoustic and loopback tests, thus making the loopback test more repeatable. git-svn-id: svn://coreboot.org/openfirmware@3623 1552c027-8020-0410-b4b5-a757f869b4ce