hdparm and hdparm -i give conflicting info about DMA status. The following post shows two systems output that are inconsistant in opposite ways. http://forums.gentoo.org/viewtopic-p-2398728.html#2398728 Reproducible: Always Steps to Reproduce: 1.hdparm /dev/hda 2.hdparm -i /dev/hda 3.hdparm -I /dev/hda compare DMA info. Actual Results: hdparm /dev/hda /dev/hda: multcount = 16 (on) IO_support = 1 (32-bit) unmaskirq = 1 (on) using_dma = 1 (on) keepsettings = 0 (off) readonly = 0 (off) readahead = 256 (on) geometry = 16383/255/63, sectors = 120034123776, start = 0 hdparm -i /dev/hda /dev/hda: Model=ST3120026A, FwRev=8.01, SerialNo=5JT4E937 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4 BuffType=unknown, BuffSize=8192kB, MaxMultSect=16, MultSect=16 CurCHS=65535/1/63, CurSects=4128705, LBA=yes, LBAsects=234441648 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio1 pio2 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 AdvancedPM=no WriteCache=enabled Drive conforms to: ATA/ATAPI-6 T13 1410D revision 2: hdparm -I /dev/hda /dev/hda: ATA device, with non-removable media Model Number: ST3120026A Serial Number: 5JT4E937 Firmware Revision: 8.01 Standards: Used: ATA/ATAPI-6 T13 1410D revision 2 Supported: 6 5 4 3 Configuration: Logical max current cylinders 16383 65535 heads 16 1 sectors/track 63 63 -- CHS current addressable sectors: 4128705 LBA user addressable sectors: 234441648 LBA48 user addressable sectors: 234441648 device size with M = 1024*1024: 114473 MBytes device size with M = 1000*1000: 120034 MBytes (120 GB) Capabilities: LBA, IORDY(can be disabled) bytes avail on r/w long: 4 Queue depth: 1 Standby timer values: spec'd by Standard, no device specific minimum R/W multiple sector transfer: Max = 16 Current = 16 Recommended acoustic management value: 128, current value: 0 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=240ns IORDY flow control=120ns Expected Results: Consistant info. refer to forum link to see opposite behaviour. hdparm dev/hdx shows DMA off whilst -i shows UDMA2* , system usage indicated it is off.
I have Use_DMA_when available in kernel. man hdparm indicates that this info is boot time info. but presumably not from before the kernel is loaded !
This is not a bug - see man hdparm hdparm -i displays "the identification info that was obtained from the drive at boot time, if available... The data returned may or may not be current, depending on activity since booting the system." hdparm -I requests "identification info directly from the drive" The output shown here means that DMA was off when booting and was turned on later on (via hdparm, kernel drivers, ...)
So how does this relate to the info posted in the thread that I indicated above: I9300 zobi # hdparm -i /dev/hdc /dev/hdc: Model=_NEC DVD+/-RW ND-6500A, FwRev=202C, SerialNo= Config={ Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic } RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0 BuffType=unknown, BuffSize=0kB, MaxMultSect=0 (maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0 IORDY=yes, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio1 pio2 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 *udma2 AdvancedPM=no * signifies the current active mode here dma is shown as being active by -i at boot. I have dma built-in (and no hdparm in init) so how can another system get output where this is on. Could it be that the BIOS turns this on before boot on the other box and not mine. Thx [*] Use PCI DMA by default when available
Of course that BIOS can turn on DMA on the other machine and not on yours... As for the forums thread, whether DMA works or not with CD/DVD writer is completely unrelated to "inconsistent" hdparm output and making the output "consistent" would not fix anything at all. Could be caused by anything from kernel miscofiguration to broken hardware, firmware bugs, k3b or other software bugs, master/slave settings and position on the cable, issues with another ATAPI drive on the same IDE cable, etc. etc.
as the manpage indicates, and like Jakub said, -i/-I may report outdated information, and the output of -I is 'displayed in a new expanded format with considerably more detail than with the older -i flag' if you have any other concerns, please the hdparm website and file an issue there: http://sourceforge.net/projects/hdparm/ they are much more likely to tell you everything you ever wanted to know
