With releases 8.04, 8.10 and now 9.04 beta I can confirm the same behaviour.
In my case the problem shows up with an MSI CD writer/DVD reader: 4.928302] ata6.00: ATAPI: ATAPI COMBO52XMAX, VER 1.40, max UDMA/100 [ 4.928318] ata6: nv_mode_filter: 0x3f39f&0x3f01f->0x3f01f, BIOS=0x3f000 (0xc700c600) ACPI=0x3f01f (20:600:0x13) [ 4.928320] ata6.00: limited to UDMA/33 due to 40-wire cable [ 4.944246] ata6.00: configured for UDMA/33 hdparm confirms that the device is capable of UDMA/100 (mode 5) but confirms that it is running at 33 (mode 2): ATAPI CD-ROM, with removable media Model Number: ATAPI COMBO52XMAX Serial Number: Firmware Revision: VER 1.40 Standards: Likely used CD-ROM ATAPI-1 Configuration: DRQ response: 50us. Packet size: 12 bytes Capabilities: LBA, IORDY(cannot be disabled) DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2 udma3 udma4 udma5 Cycle time: min=120ns recommended=120ns PIO: pio0 pio1 pio2 pio3 pio4 Cycle time: no flow control=227ns IORDY flow control=120ns A UDMA/133 hard disc on the same motherboard is no problem:- 4.728459] ata5.00: ATA-7: Maxtor 2F030J0, VAM51JJ0, max UDMA/133 [ 4.728462] ata5.00: 60058656 sectors, multi 1: LBA [ 4.728480] ata5: nv_mode_filter: 0x7f39f&0x7f01f->0x7f01f, BIOS=0x7f000 (0xc700c600) ACPI=0x7f01f (15:600:0x13) [ 4.744392] ata5.00: configured for UDMA/133 This had previously been reported under bug 285595 -- Wrong UDMA mode due to error in 40/80 wire cable detection https://bugs.launchpad.net/bugs/323302 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs