Beware using other people's DSDT

uman · #1 08-02-2009, 06:57 PM

Many newbies don't understand that you shouldn't be using DSDT's generated on other people's computers. I think everyone knows by now that you shouldn't use one from a different make and model, but many noobs assume that one generated on the same make/model is okay.

It ain't.

A DSDT can be very system specific. For example, my DSDT has this code:

Code:

OperationRegion (GNVS, SystemMemory, 0x7F697DBC, 0x0100)

But another one (also with 2GB) has this:

Code:

OperationRegion (BIOS, SystemMemory, 0x7F7AE064, 0xFF)

While one with 1GB may have this:

Code:

OperationRegion (BIOS, SystemMemory, 0x3F7AE064, 0xFF)

If you use one with an incorrect memory specification, you could get all sorts of strange symptoms.

So don't share needles, err... DSDT files. Make your own.

-u

Gurruwiwi · #2 08-03-2009, 02:33 PM

hahahah !!

Got a great laugh out of that last liner!

But so true...

uman · #3 08-04-2009, 02:57 PM

Thanks. I hope that over time this subforum can be a good repository of DSDT tips & tricks. We should also think about pulling out individual bits (like some of candycane's posts) into individual posts with relevant titles and tags...

-u

DocShadow · #4 08-04-2009, 06:16 PM

So .. are you implying that anytime I change my system hardware I should remake the DSDT or are there only certain hardware changes that affect the file?

Thanks

uman · #5 08-05-2009, 05:54 PM

I'm not sure about other types of changes. But if you change the amount of RAM installed, you should remake the DSDT.

Whether you need to do it for things changes to audio, graphics, firewire, etc., will depend on whether you have customized your DSDT to support audio, graphics, firewire etc in some way.

If you don't have extensive customizations to your DSDT then I doubt very much that changing your hard disk, graphics card or audio card, etc., will change your DSDT.

But it's a testable hypothesis. Save your old DSDT.dsl file, and then generate a new one after installing your hardware. Diff the two (if you have Xcode installed, you can use opendif from the Terminal) and see if there's any changes.

If you do find changes, post back here so we can all learn some more mystic DSDT tricks...

-u

Quote:

Originally Posted by DocShadow

So .. are you implying that anytime I change my system hardware I should remake the DSDT or are there only certain hardware changes that affect the file?

Thanks

DocShadow · #6 08-05-2009, 06:59 PM

I just updated my BIOS and made a new DSDT file so I'll practice on that.

adriangb · #7 04-01-2010, 04:30 PM

Thank's for the tip. I had been thinking lately that there must be some difference in system's DSDT's (I even read about the RAM one somewhere, but I wasn't sure until I read this, I guess that means I'm still a noob).
It would be nice to have a thread with all those obvious assumptions that noobs not unlike me always make, and are incorrect.
@ DocShadow: I'm pretty sure that SATA info for the drives is on a other table, I remember seeing some SATA code on an SSDT (not the same one that had the CUP0CST etc), It might be that...

artimess · #8 05-04-2010, 09:44 PM

Quote:

Originally Posted by uman

Many newbies don't understand that you shouldn't be using DSDT's generated on other people's computers. I think everyone knows by now that you shouldn't use one from a different make and model, but many noobs assume that one generated on the same make/model is okay.

It ain't.

A DSDT can be very system specific. For example, my DSDT has this code:

Code:

OperationRegion (GNVS, SystemMemory, 0x7F697DBC, 0x0100)

But another one (also with 2GB) has this:

Code:

OperationRegion (BIOS, SystemMemory, 0x7F7AE064, 0xFF)

While one with 1GB may have this:

Code:

OperationRegion (BIOS, SystemMemory, 0x3F7AE064, 0xFF)

If you use one with an incorrect memory specification, you could get all sorts of strange symptoms.

So don't share needles, err... DSDT files. Make your own.

-u

Could you please explain to me where those hex numbers are coming from and where, which book or source one can find them. I am not only talking about systemMemory, but there others in any DSDT with some sort of hex addresses.

Thanks
Artimess

Drule · #9 05-18-2010, 05:22 PM

I created my first DSDT file from Windows, using DSDTse for Win, while I still had AHCI disabled. Then after enabling AHCI, disabling the serial and parallel ports in the BIOS, plugging in and turning on all eSata drives I generated another DSDT.dsl from Windows. As I don't have Xcode installed, I can't diff them, but if you like I can upload both DSDT.dsl files (or attach them to a post) if they would be of any use to the pros ....