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Full Version: How To Change Hd Udma Mode
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While reading trough the forum, I've found that you can see info on you're hd with hdparm -i -v -t.

Here is mine :

multcount = 16 (on)
IO_support = 3 (32-bit w/sync)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 16 (on)
geometry = 39704/16/63, sectors = 40021632, start = 0


Model=Maxtor 5T020H2, FwRev=TAH71DP0, SerialNo=T2JC479C
Config={ Fixed }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=40021632
IORDY=on/off, 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=yes: disabled (255) WriteCache=enabled
Drive conforms to: ATA/ATAPI-6 T13 1410D revision 0: 1 2 3 4 5 6

QUESTION : how can I overide udma modes , in case they were not detected correctly? [and to make that change permanent].
and how can I make this change permanent hdparm -u1 -c3 -a16 /dev/hdc
Timing buffered disk reads: 64 MB in 2.21 seconds = 28.96 MB/sec
[root@robi2kv12 root]# hdparm -t /dev/hdc

Timing buffered disk reads: 64 MB in 2.15 seconds = 29.77 MB/sec
[root@robi2kv12 root]# hdparm -t /dev/hdc

Timing buffered disk reads: 64 MB in 2.16 seconds = 29.63 MB/sec
[root@robi2kv12 root]# hdparm -t /dev/hdc

Timing buffered disk reads: 64 MB in 2.15 seconds = 29.77 MB/sec
[root@robi2kv12 root]#

Question : how come I get same disk read with udma2 [just as another user got it with udma5] ?

By the way the computer is :

AMD XP 1700XP [oc 2000Mhz] 10x200
512 MB DDR 400
Gigabyte nForce2 Ultra Pro 2
80GB Quantum ATA133
60GB Quantum ATA133
40GB Quantum ATA100 [reported by bios] but Linux uses udma2 instead [I guess this is not 100, it's rather 33 or 66?]

Robert B
In linux, the controller will only write as fast as the slowest device on a bus ... if your hard drive is on the same bus as your IDE cdrom and if it is udma2 then the hard drive will also be at udma2.

here are the udma modes and hdparm -X switches:
-X66 is ata33 ( udma2 )
-X68 is ata66 ( udma4 )
-X69 is ata100 ( udma5 )
-X70 is ata133 ( udam6 )

But that is reallt burstable speed and not normal transfer rates ... for example:

Here is a system with hda at udma4:
Timing buffered disk reads: 64 MB in 1.94 seconds = 32.99 MB/sec

and hdd at udma2:

Timing buffered disk reads: 86 MB in 3.05 seconds = 28.20 MB/sec
Looking at the specs of your motherboard, I should support udma6 transfers ...

You can try passing in:

ide0=ata133 ide1=ata133

on the end of your kernel line (in /boot/grub/menu.lst) and see what happens on reboot

as for doing permanent changes in RedHat, the easiest way is this:

edit the file /etc/sysconfig/harddisks

set it to look like this:

EXTRA_PARAMS="-u1 -a32"

after rebooting, issue the command:

hdparm -i /dev/hdc


hdparm -v /dev/hdc

If everything else looks good, try this command:

hdparm -X69 /dev/hdc

Then do hdparm -i /dev/hdc again and see if it shifts to udma5 mode....

If it does and it works OK, add -X69 to the EXTRA_PARAMS="-u1 -a32" in /etc/sysconfig/harddisks, so it would be like this:

EXTRA_PARAMS="-u1 -a32 -X69"
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