I'm seeing some interesting behavior when I perform a Linux reboot when the OS is loaded on particular models of compact flash drives.

A customer reported this problem using some later version of RH and I was able to recreate using Puppy Linux 4.2.1.

The CF drive resides on a PCI card with a SIL680 PCI/ATA controller.

When linux system is shutdown and then powered up everything boots fine. If linux system is rebooted then the system hangs and you have to power down the system. This problem occurs on more than one brand of CF but works fine with other brands.

When I load XP onto problem CF drive, reboot works fine.

So it appears to be something that Linux does in particular during a reboot.

My theory is that Linux must put CF drive into sleep mode or something and a reboot does not reset it out of this mode like a full powerdown does.

Two issues.

One is the ejecting of the CF I'd think. Once it ejects it stays that way over a reboot. I have seen it even on usb flash drives.

Other idea is.


For maybe the last 25 years this has been a common issue.

A reboot is not a shutdown.

Your system has not fully cleared all the registers before it rebooted. So the state is unknown.

After sorting thru various traces it doesn't really appear to be a CF problem but how certain CF drives perform to an odd BIOS sequence. Basically the BIOS sets the CF drive to operate in PIO mode and then issues a DMA command. At powerup it seems to work fine for some reason. During reboot the last thing linux does is write to the disk in UDMA3 mode. Reboot of Window XP works since last write it does to disk is write in PIO mode so it is already operating as on powerup. The last thing Windows XP does to disk is a flush cache which I would advise that Linux incorporate into their reboot/powerdown sequence. It would probably be good to do the SLEEP command before powering down as well. This would spin down the drive before powering down and make hard drives last longer.

Some CF drives work since their reset does reset to as it is on powerup while others do not. So much as jefro says "A reboot is not a shutdown".