What does the long beep sound when booting up with a DS3 Mobo mean?

It's not the regular quick beep, it's as soon as I boot, and sometime around the memory post I get this long 1-2 loud beep, but the computer continues to boot fine. What does this mean?

This was only happening when I had the CPU overclocked.

Specs
Core2Duo E6600
2GB (2x1GB) Patriot DDR2 667Mhz RAM 4-4-4-12 (1.8V)
Sapphire X1800XT
WB 250GB SATA 3.0Gb/s 16MB Cache
550W Ultra X-2 Connect PSU
Gigabyte 965P-DS3 Mobo