Modifying ACPI tables in bios to add additional processors?

[fleabag]

Since HT was on the orginal P4 processors, I was wondering how possible would it be to change the ACPI tables in the bios to "access" the HT function of the older P4 processors that claim to "not have HT"? Also I was wondering if say on a PIII motherboard, could you modify the ACPI tables and make windows think that there are two processors when there is really just one. While process' will be fighting over CPU time, I feel that there is something to be gained by convincing windows that there are two physical or two logical processors.

Now this brings up my next question, is it possible to change the ACPI tables on a dual socket motherboard to say that the second processor is a logical processor instead of a physical processor. One of the reasons I'd see doing this is to allow the function of the second, physical processor on an OS such as XP Home edition.

Moved from General Hardware
General Hardware Moderator -- MarcVenice

 

[PottedMeat]

There are P4s that claim not to have hyperthreading but actually do?

What would be gained by having Windows think there are two processors when the hardware cannot physically do the work - are there some strange optimizations the Windows scheduler makes with imaginary hardware hehe?

 

[CTho9305]

Just changing the data structures that report CPU information is guaranteed to not work. You can't trick an OS into trying to run multiple threads simultaneously on a single processor just by telling it there are multiple CPUs present and having it try to use them.

When you are using a multi-threaded core or multiple cores, there's a process you have to go through to initialize extra cores... for AMD CPUs, it's documented in the "BIOS and Kernel Developer's Guide". I assume there's an equivalent Intel document somewhere. Keep in mind that the functionality is probably impossible to enable (i.e. disabled with fuses), and that everything I've read indicates that HT was turned off primarily because it didn't work properly in the early revs.