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Notes:
1: These vipers have large pc104 interrupt rates. Occurs with both Sep 14 (a1,a8) and the Oct 4 (a5) kernels.
2: Not completely sure why on m21 the IRQ3 rate is less than the pc104 load. Perhaps that version of the pc104 irq routine exits if pending bits are 0.
3: High USB interrupts are seen on vipers with bluetooth radios interfaced via USB. Not High USB interrupts are not seen on Titans, even though on a1-19 "A" site titans, USB serves both the bluetooth radios and flash drives are USB. On a1-19 "A" site Vipers, USB has only bluetooth radios are on USB. Assume it is due the different USB interface chips. Viper USB driver is isp116x_hcd. Titan USB driver is ohci_hcd.
4: On c20,m21, m22, USB is used only for flash drives
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Vipers at a2, a6 and c20 are OK.
The viper kernel has a patch to use an assembler delay function for the isp116x, and not the kernel ndelay() function. Don't think this is related though.