Ensuring DMA is on using registry key

  • Thread starter Thread starter Mark M
  • Start date Start date
M

Mark M

I was checking over my XP Pro system to make sure that DMA was being
used on all drives.

I came across this website at:
http://www.blackmaxpc.com/Guides/Enable_DMA.htm
where it says to go to this registry key ...

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-
E325-11CE-BFC1-08002BE10318}

and then it says to "Be sure the DWORD EnableUDMA66 or EnableDUMA100
as the case may be, is there and in each directory. If not you will
have to create it."

I took a look at that registry key on my system and found that (a)
there were 18 of them and (b) the word "enableUDMA" does not occur in
any of them.

(1) Why do I have so many entries for that key? Is it because I
often swap drives in and out of the system? I usually use about five
different hard drives in my PC so 18 entries seems like a high
number.

(2) Is what the website says about that "Enable UDMA" text being
there in the key actually true? Maybe it applies to XP Home and I
have XP Pro?
 
Mark M said:
| I was checking over my XP Pro system to make sure that DMA was
| being used on all drives.
|
| I came across this website at:
| http://www.blackmaxpc.com/Guides/Enable_DMA.htm where it says
| to go to this registry key ...
|
| HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E
| 96A- E325-11CE-BFC1-08002BE10318}
|
| and then it says to "Be sure the DWORD EnableUDMA66 or
| EnableDUMA100 as the case may be, is there and in each
| directory. If not you will have to create it."
|
| I took a look at that registry key on my system and found that
| (a) there were 18 of them and (b) the word "enableUDMA" does
| not occur in any of them.
|
| (1) Why do I have so many entries for that key? Is it because
| I often swap drives in and out of the system? I usually use
| about five different hard drives in my PC so 18 entries seems
| like a high number.
|
| (2) Is what the website says about that "Enable UDMA" text
| being there in the key actually true? Maybe it applies to XP
| Home and I have XP Pro?
Click to expand...


Eric Gisin said:
The enableudma value was used in the original Win2k for
UDMA/100, but is not need after SP1. I doubt WinXP used in. I
have found errors on every tweaking site.

I don't know why you have more than the default 3. I move drives
around too.
Click to expand...


Eric, thanks for the info. I suspect I may have those extra registry
entries because I used the reg tweaking utlity on that same web site
above.

Do you or anyone else know how I can safely prune the number of keys
down to the original three?
 
| > I don't know why you have more than the default 3. I move drives
| > around too.
|
| Eric, thanks for the info. I suspect I may have those extra registry
| entries because I used the reg tweaking utlity on that same web site
| above.
|
| Do you or anyone else know how I can safely prune the number of keys
| down to the original three?

I would never do it with regedit. You should be able to see them in device
manager if set an environment variable:
support.microsoft.com/default.aspx?scid=kb;en-us;241257
 
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