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Xp Has Drive Locked In Pio Mode. Dma Unavailable.

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#1 NorCal_Mike


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Posted 04 October 2007 - 01:38 AM

After much investigation, I think I've discovered why my Sony laptop's been running SO slow. The following, taken from another site, mirrors other things I've read today about this problem:

"A maddeningly understated problem arises with how Windows locks down what it thinks is the best transfer mode for each of your IDE devices. After the initial hardware detection, XP keeps a running tally of the number of times a drive fails access attempts. When this cummulative number reaches six, it reduces the compatibility mode and tries again. At first XP will try downgrading within the same transfer method, eg: from UDMA Mode 4 to UDMA Mode 3, but when these sublevels run out it will assume DMA is no longer available and permanently fail back to PIO Mode, because the transfer mode tweaking is one way (downwards)."

Mine is currently locked in PIO mode, apparentlywith no easy way to get back to the higher DMA transfer rate I formerly enjoyed. One site suggests uninstalling the driver, then rebooting, which is somewhat scary, as I wonder how it'll shut down properly and reboot with NO driver. The site the above description came from provides a series of steps which call for editing the Registry, which is even more scary -- tho' I have done some of that before.

I'm using XP Home Edition w/ SP2
Sony Vaio VGN-FS742, w/ 80GB HD, which is the IDE device with the problem. (It's not my DVD burner, as is often the case with others.)

The slowness is not related to some of the more obvious things some might suspect:

* Almost 70% of the HD is free space.
* The drive's recently been fully deep scanned for viruses, malware -- all that -- which turned up nothing.
* Ran chkdisk (/f/r) this afternoon, which found & repaired two minor bad clusters: sys32\dsound.ll and sys32\hhctrl.ocx, files 7200 and 41303
* HD was defragmented yesterday (3% at the time)
* Running bare bones with respect to startup or background programs, tho' not entirely sure about all Services.

In the interest of sticking to one issue at a time, I'd just like to address the best way to get my drive back to DMA, ASAP, and will ask about other things another time. Thanks in advance for any concrete suggestions.


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#2 NorCal_Mike

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Posted 04 October 2007 - 03:33 AM

I found the fix, and it's so cool and fast that I have to pass it along to others. First, I'd just like to say that I've learned today that this problem is more prevalent one might imagine. Windows is SO sneaky, with respect to how it changes your DMA transfer mode progressively lower until it is finally locked in the slowest of PIO modes, that most are completely unaware it's even happened! Meanwhile, their system is running like a tortise instead of the hare it once was, as running in the PIO Mode causes a host of issues/problems.

The site I found the fix on, right at the top of the page, is: http://winhlp.com/node/10. They provide an in-depth explanation of the problem and a few different ways to fix it:

(1) You can download a very small program in Visual Basic, which will reset your drive to DMA on next reboot. This was my choice. After downloading, viewing it in Notepad, and running Norton on the file, I ran the fix in mere seconds. Upon reboot my IDE Drive is running in Ultra DMA Mode 5!! FINALLY, my system is screaming again.

(2) They offer step-by-step manual instructions for those who have any fears that the program could be malevolent, plus a couple other options.

Anyone having problems with a "slow" computer, or problems with their DVD burner (which seemingly causes this more often than a HD) ought to check out this setting on their system. One final note, laptops seem to be more prone to this, since going into and coming out of Standby Mode can cause the errors, which in turn causes Windows to continually ratchet down the DMA Mode settings into the slow (antique) PIO Mode -- and after it hits bottom, it stays there.

This was a Godsend for me. Hope it helps someone else.

#3 WinCrazy


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Posted 04 October 2007 - 11:57 AM

Hi NorCal_Mike.

This is a great fix! :thumbsup: Nice researching.

If I understand this correctly, this fix sets DMA modes to bothe IDE/ATA hard drives and optical drives.

#4 hamluis



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Posted 04 October 2007 - 12:07 PM

Getting back to DMA mode in Windows XP - http://sniptools.com/tipstricks/getting-ba...e-in-windows-xp

This works for me. I've moved drives around a lot and sometimes wind up with a harddrive on the optical drive connector...and run into the situation described.


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