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How to force DMA?



A friend of mine has an old AMD K6-2 550 system and I installed a new hard drive for him. A Maxtor ATA100 20 GB HD. The hard drive is detected at UDMA 4 (ATA66 I believe) by the motherboard and everything is fine, but windows detects it as PIO mode 4 and not even as UDMA/33 or even regular DMA. He has an AT PCChips motherboard with integrated video and sound with the SIS 530/5595 chipset. I don't remembet the exact model. All with the latest bios. I checked and XP is set to use DMA if available but still only uses PIO 4 which makes his system very slow as HD acceses easily eat up a large portion of the CPU time. I need to know how to force XP to use DMA, any DMA even if not UDMA if at all possible.



Have you tried getting the latest IDE drivers for XP. You're most likely to find some on your friends chipset internet site.


I tried, the SIS website doaes not have specific XP drivers, only 2000 drivers and they are dated earlier then the XP default drivers. Should I install the SIS drivers anyway? If I do, were can I find the XP drivers if something goes wrong?



I don't know if they will work, but I don't belive there is any harm in trying. I had a simular problem, and tried to install the VIA IDE drivers. They totally screwed up my computer, but it was just to load a previous restore point and everything was back to before the driver.

Anyways, SIS might be better at making drivers than VIA, and 2k drivers are usually compliant with XP drivers, so you sould give it a go.


You may want to search the other forums here for a post about making an "EnableATA66" key in the registry. I'll check around here and some places and if I find a link or the registry hack, I'll post it here.


I downloaded the SIS drivers for win NT/2000 but when I try installing them XP gives me the propt that it could not find drivers for my hardware. I hate this the most about the newer MS operating systems. They search and only look for a maching driver. I uninstalled the old XP driver and am trying to install with add hardware wizard but when I pint to the driver file windows XP says this location has no drivers for my hardware.

I need help to install the driver. Basicaly I need a way so that windows will just give me a list of drivers in some folder like I want instead of tell me that it does not mach my hardware. Or maybee somebody knows how I can change the hardware identification string in the INI file to trick XP into installing the driver.

Thanks in advance for any help.


OSNN Addict
Many hard drive controllers switch both channels on the controller to the lowest common denominator device's access mode -- in other words, if you have a UDMA and a PIO device on the primary controller, your whole primary controller will only work under PIO.

If there's a CD-ROM drive on the same controller as this hard drive, remove it or move it to the secondary controller. Most CD/DVD-ROM drives are PIO, and will cause this very issue on said motherboards/controllers.


Nope, he has the hard drive on the Primary IDE only and then a burner on the Secondary which I believe is capable of DMA/33 and is also detected as PIO.

My concern right now is no longer to try to enable DMA but to try and force XP to install the SIS IDE drivers for win 2000 and see if maybe the older SIS drivers will support DMA properly.


Windows XP will take a drive to the highest level it will allow, UDMA-5,4,3,etc. If it can't run the drive at that level it takes it down one, like if its running at 5 it goes down to 4, if it can't run at 4 it goes down again. So if the drive is ending up in PIO mode, then it is due to the IDE drivers , a jumper on the drive, or the BIOS. It is probably due to the IDE drivers though.

To install the driver you will have to choose the Let me choose the driver to install, and when it gives you a list of options, and hardware click on Have Disk... and point it to the INF file of the drivers. DO NOTE HOWEVER, that many Windows 2000 IDE drivers WILL NOT work on XP, due to NTFS 5 not being the same as NTFS 5.1 and you will not be able to boot into XP, so make SURE you backup your config before installing the W2k ide driver.


I do not use NTFS and I have tried choosing the driver from a list and then have disk and selecting the ini file. That is when XP says that this location has no information for my hardware and what I need to do is somehow forece windows XP to install the driver anyway without checking it.



Same chipset and same problem

I am also haveing the same problem. Sadley however I am still not able to get DMA enabled on my computer. I've tried almost everything (Including IDE drivers from the SiS website) and the result NOTHING! It is really dissapointing, I have a dvd player that is not able to work because of PIO mode, and I enjoy the OS very much and have to much already configured and saved to go back to Me or 98. I hope somebody has a solution to this problem. Thanx in advance for y'all help.

P.S. I tried the reg hack (you know the one where you delete the Slave and Master values. The solution offered in the link.) and this did not fix the problem.


I do succeed

I'm French, please excuse me for the accent ;-)
I have a laptop (Gericom Overdose... P3-1GHz...SiS 630 or 640 Chipset) with WinMe installed, UltraDMA successfully enabled for the HDD (Chan1, Master) and the DVD drive (Chan2, Master).
I have formatted the HDD (Fujitsu [...]) and installed WinXP. The HDD has been set on "DMA if available" but run in PIO mode (no problem for the DVD drive).
SiS IDE drivers for XP not on SiS Web site :-(
I set the HDD in PIO mode only, then reboot. After that, I set back the HDD in "DMA if available". OK. Properties again, read at Active Transfert Mode : UDMA Mode 5 ! Victory !

PS : setting the empty connectors's peripheral type to "None" may help (I have done this)


If the system uses UDMA and UDMA is enabled in the bios. You may not need to set it in the operating systems.
Infact doing so. Sometime creates the disappearing CDROM affect.


Thanks pinkshark, you were right, I set it to PIO only mode for drives and none for the free conections, restarted and then set to DMA if available and the system has UDMA 4 for the hard drive and Multi-wird DMA for the burner.

I'm not sure what actualy did it but thanks.

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