> I made a new discovery. And this nails it :-) > So then I ran > dd if=/dev/mem bs=4 count=1 skip=$((0xfc5c080/4)) | od -t x4 > a few times very fast, plucking the first affected word directly out of > memory by its physical address. The result: > > The low 16 bits are always zero as before. The high 16 bits are a counter, > being incremented at about 1000Hz (as close as I could measure with a > crude > shell script. 1024Hz would also be within the margin of error). And it's > little-endian. > So what type of driver, firmware, or hardware bug puts a 16-bit 1000Hz > timer > in memory, and does it in little-endian instead of the CPU's native byte > order? And why does it stop doing it some time during the early init > scripts, > shortly after the root filesystem fsck? It looks like it is the frame counter in an USB OHCI HCCA. 16-bit, 1kHz update, offset x'80 in a page. So either the kernel forgot to call quiesce on it, or the firmware doesn't implement that, or the firmware messed up some other way. Segher -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>