# No DMA on disks (Asus K8VSE Deluxe motherboard)

## MFA

Hi,

The DMA on my disk(s) aren't running. The fact that DMA isn't enabled is obvius when you look at the poor preformance, and because reiserfs.fsck warns me that DMA is disabled..

So I tried doing a `hdparm -d1 /dev/hdb` (yes, /dev/hdb _is_ my main disk), but I get a

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hdparm -d1 /dev/hdb

/dev/hdb:

 setting using_dma to 1 (on)

 HDIO_SET_DMA failed: Operation not permitted

 using_dma    =  0 (off)

--

And I'm pretty sure DMA is enabled in the kernel (Gentoo-2.6.10), because a quick grep thourgh the config file of the kernel gives::

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cat /usr/src/linux/.config|grep -i dma

CONFIG_GENERIC_ISA_DMA=y

CONFIG_BLK_DEV_IDEDMA_PCI=y

CONFIG_BLK_DEV_IDEDMA_FORCED=y

CONFIG_IDEDMA_PCI_AUTO=y

# CONFIG_IDEDMA_ONLYDISK is not set

CONFIG_BLK_DEV_IDEDMA=y

# CONFIG_IDEDMA_IVB is not set

CONFIG_IDEDMA_AUTO=y

--

So now I'm lost... a chance me be that the chipset is unsupported, but before a kernel-upgrade DMA worked, so now I just don't know which module to load in order to regain DMA on my disk? - anyone know?

Morten Fangel

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## moocha

Well, which chipset are you using?

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## MFA

Hmm, not sure which one of them is for the disks, but the following two:

VIA K8T800

VIA VT8237

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## NeddySeagoon

MFA,

Probably neither of them.

Can you do a lspci and post the line(s) with IDE in please?

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## moocha

VT8237 is the south bridge, which includes the IDE controller. Disable the generic IDE stuff (Generic/default IDE chipset support and Generic PCI IDE Chipset Support) since it slows things down, and enable CONFIG_BLK_DEV_VIA82CXXX (VIA82CXXX chipset support ). Do not compile it as a module. Build it into the kernel.

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## MFA

Well, I don't know if it actually is one of them, but i did a grep for "via" in the kernel-config, and found out that "CONFIG_BLK_DEV_VIA82CXXX" wasn't set, so I simply enabled it (with [y]) and now it works... 

great

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## MFA

moocha -> yep, you were right, the VIA module (well, not not as a module, but still) did the trick... I might try out the disabling of the Generic IDE one day, but for now, this is great... a rough test (can't remember the original measures)

Before:

 Timing cached reads:   2316 MB in  2.00 seconds ~= 1050 MB/sec

 Timing buffered disk reads:  120 MB in  3.01 seconds ~=  6.5 MB/sec

After: 

 Timing cached reads:   2316 MB in  2.00 seconds = 1155.86 MB/sec

 Timing buffered disk reads:  120 MB in  3.01 seconds =  39.90 MB/sec

So a nice improvement..  :Wink: 

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