The Silicon Graphics SGI O2 boot chime #VintageComputing #RetroComputing @TheMogMiner

Twitter user @TheMogMiner provides some history on the Silicon Graphics (SGI) O2 machine boot chime:

It’s not a sample, the plucked string is generated live using the Karplus-Strong method. It relies on uninitialized memory. It relies on values that are both unusually large, and unusually small, for single-precision floats.

Even in MAME’s MIPS interpreter, it hits the FPU so hard that +/- infinity comes up, then it explodes, because the boot PROM isn’t set up to expect exceptions at this point. “I mean, the architect was either a certified genius or an authentic wacko.” – Dr. Ray Stantz

The routine seems to have a legit FP divide-by-zero, and due FP exceptions being turned off by the boot PROM, it produces a result that doesn’t propagate denorms.

See the example posted on Twitter.

Here are some other examples posted on YouTube: Example 1 and Example 2


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