upgrade to 5.1.4 breaks XP mode hack

[csmccarron]

Ok, I am not trying to be difficult but I think I covered the posters question on the How To part which would mean the post is resolved. Its working for me and I know how to reproduce going forward. My only wish would be if possible, can VirtualBox support XP Mode as an option in the future?

Regards,
Chris McCarron

[Sandshark]

While I am not the original poster, just a "me too", I had no trouble following your instructions and it did, indeed, resurrect the "XP Mode Hack". It was not necessary to do anything but create the file and replace the old with the new. No need to re-issue the VBOXMANAGE command to specify the BIOS (which may or may not be changed/broken in 5.1). I would expect most anyone who follows this forum should have no trouble doing the same.

One question left a bit unclear is for the future: Is the 913A offset always the correct place for the string? I'm thinking the answer is yes, but would you please confirm?

Thank you ever so much for your efforts. Have a virtual beverage of your choice on me.

[mpack]

One question left a bit unclear is for the future: Is the 913A offset always the correct place for the string? I'm thinking the answer is yes, but would you please confirm?

Your question is a tad ambiguous. It could mean "does the hack only work if the string is at x913A?" or "is it always safe to trample over the previous bytes at x913A"? I'm not aware of what supporting data you would use for either conclusion.

IMHO, instead of hacking an existing BIOS, it would be a lot safer to recompile the BIOS code, using pragmas if it all possible to properly locate this string at the necessary offset.

[csmccarron]

That appears to be the location of the PKey in the SLIC BIOS information. See images on my earlier post.

[mpack]

I'm not sure that answers anything. Are the SLIC tables at a constant address? I'd have thought not. I'd have guessed that you call a function to get a SLIC table pointer. I could certainly be wrong, but I don't see why a modern BIOS would locate things at fixed addresses. Rather, it would be inside some range. Still, if it works (now) then it works.

[Eaxun]

Yes, this is another "me too".
My opinion is this is an issue about backward compatibility. Why a virtual machine that was running perfectly in version 5.0 is not working anymore?
After updating to version 5.1 (and Anniversary Update), I am sure that many users have the same problem and are really concerned about their daily job with old applications.
Since this an issue, I think it should be, as soon as possible, a patch to fix it.

[socratis]

After updating to version 5.1 (and Anniversary Update) ... daily job with old applications.

Have you considered to not update your system if you depend on it? I know a lot of people that are still using VirtualBox 4.3.x on Windows XP/7. The reason? Their old VMs depend on it, and they depend on their VMs.

I'm not saying that you shouldn't update. I'm saying that if you depend on it for your day-to-day operations, you should double-consider it and triple-test it before you do.

[mpack]

Yes, this is another "me too".
...
After updating to version 5.1 (and Anniversary Update), ...

That makes it not a "me too". If you're running a Win10 host then you don't have an XP license, and it has never been our intention to help people breach copyright. In fact this was already made clear above.

[csmccarron]

@Sandshark,

The original pcbios file was using a VirtualBox BIOS from v4. It would appear that VirtualBox v5.1 altered the BIOS, this is to be expected, is such a way it broke the XP Mode Virtual Machine. From this point forward when a major release comes out, I intend to go thru the process again to make sure my XP Mode machine is using the correct VirtualBox BIOS.

@mpack,
I do not know much about how a BIOS works so I am not sure if those addresses are fixed or not. So is it possible to compile the BIOS into a BIN file? Are there instructions available on how to do this?

Thanks,
Chris McCarron

[hd]

I can't thank csmccarron enough for his detailed solution. Saved me days of work of upgrading, rolling back to working snapshots, testing, verifying, etc. The first time I googled VB 5.1 pcbios was back in early August, and until a few weeks ago, I didn't even think anyone had a use for this hack anymore.

Thank you very much csmccarron, I think a lot of us owe you a beer.

[mpack]

I do not know much about how a BIOS works so I am not sure if those addresses are fixed or not. So is it possible to compile the BIOS into a BIN file? Are there instructions available on how to do this?

There is nothing except the normal VirtualBox OSE build guidelines - which would of course create a new BIOS ROM along with everything else. I did take a look at the source code and I saw that VirtualBox seems to use some kind of preprocessing step (not just the C preprocessor) to include and exclude modules in the BIOS. I think the resulting file is a monolithic single source file intended for the GNU assembler (I glanced at it and saw assembler - I didn't study it). I'd have thought it was possible to modify the monolithic file for your needs, but I wasn't sufficiently motivated to work out the details, as none of my XP VMs derive from XP Mode, and I don't really recommend that anyone else's should be either.

[csmccarron]

@mpack, Thanks for the info.

[bmn]

New pcbios.bin

Attachment: bios.txt

[mpack]

I think a little more information than that is appropriate. What is this file, where did you get it, what has been done to it, and do you have a right to distribute it?

I have removed the attachment pending this explanation.

[csmccarron]

Please do not PM me asking me to send the PCBIOS.BIN file. I will not do it! The instructions are posted for users that legally own Windows 7 Professional and want to use Virtualbox as the VM host instead of the default Microsoft option. You MUST own a legal copy of Windows 7 Professional to run the Windows XP Mode virtual machine and you need to extract the BIOS file yourself!