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Author Topic: Introduction For Beginners (OSX86)  (Read 10174 times)
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« on: May 30, 2010, 05:04:47 am »

Introduction For Beginners

This guide is prepared for newbees of OSX86 who are interested to run OSX on their ordinary P.C. but not aware with OSX dictionary. Most of migrator comes from Windows platform & never heard about Kernel,Kext,Vanilla etc. Forums are the best place for finding information.I have collected some information from the major OSX86 sites about these basic terms lets take a quick look.

Q. What are kexts ?

Ans. Kexts, or kernel extensions are drivers that are installed to /System/Library/Extensions/.Kext files often have the “.kext” extension and allow for extra hardware support and and in the case of OSx86, to replace Appleʼs original drivers with ones that are optimized for use on PCs.

Where are kext located?
kext are not files rather a folder (disguised as a file),

Leopard holds kext files/folders in the /System/Library/Extensions folder,
at boot time the relevant kext are uploaded from Extensions.mkext this is a cachefolder that contains kext related to the installed hardware,

you can delete it, if Leopard can’t find it, it will create it again,

you can also state to rebuild it from darwin prompt at boot time using the switch -f see this post for further information.
How to Install a new Kext?

cd /System/Library/Extensions
mv KextName.kext KextName.old (where kextName stands for the kext you want to replace)this will rename the kext and this way back it up, it is highly recommended, warmly advised, very important to follow this step, it saved my OS many times

cd /path/to/new/kext (put your downloaded kext path here)
cp -R KextName.kext /System/Library/Extensions

next you need to fix permissions so the kext can be executed by OS user (root/system)
cd /System/Library/Extensions
chmod -R 755 KextName.kext
chown -R 0:0 KextName.kext (this will set the ownership on files to system user (root))
rm /System/Library/Extensions.mkext (this will reset all kext caching done by OSX)

Q. What is a kernel ?

Ans. A kernel is in short terms the “core” of the operating system. It controls basically all low level operating functions. Kernels exist in all Linux and UNIX based systems, including Mac OS X. In Mac OS X the kernel is located in the root of your hard drive (/) and is named “mach_kernel” by default. If you have a vanilla based system (see below) then replacing the kernel is most likely not necessary, however if you have an AMD or SSE3 incapable processor then a patched kernel will likely be required.

Q. What is DSDT ?

Ans. DSDT is a part of ACPI. Actually DSDT tells OS how to interract with the hardware (simplified way of telling it). OSX has an incomplete ACPI implementation which supports only a subset of DSDT. By replacing DSDT we can declare essentially the same interface but in the way that OSX understands. This potentially can solve nearly any ACPI-related problem (except if OSX bypasses ACPI). Other usage case is emulating by the means of DSDT features or hardware components not present on your system. But this is limited to devices that use ACPI.

Q. What is DSDT patching?

Ans. This is an area very rarely delved into, and is something that some of even the most experienced users dare not venture. In reality, its not dangerous, it just can be painfully hard at times. DSDT is a table found in your computerʼs BIOS that controls ACPI (power, time, etc.) functions. Starting at OS X 10.5.6 Apple decided to start checking for faulty DSDTs when it boots. Obviously the PCs DSDT comes back as faulty so it will not boot. The only way to counteract this is to make a dump of the DSDT in the BIOS and patch it properly for Darwin. First of all, you need a modified bootloader that will support DSDT override. This installer includes just that, using the “Install PC_EFI v9 Chameleon Edition 1.0.12” checkbox. Now you need a patched DSDT file that will be copied to / dsdt.aml. To create DSDT dumps you can use the DSDT Patcher (also included in the Extras folder) but this is an advanced method, and often UOI plugins will include a DSDT file that you can install easily with this installer. However beware, even if you have the same motherboard DSDTʼs can vary by BIOS version so try to make sure that you have the same BIOS version as what is specified in the plugin.

Q. Difference between SMC & RTC ?

Ans. The SMC is basically System Management Controller. By resetting the SMC you can resolve some computer issues such as not starting up, not displaying video, sleep issues, fan noise issues, and blah-2. While The Real Time Clock (RTC) is a chip on the logic board that controls the date and time functions of the computer. If the computer is experiencing a booting issue, resetting the RTC may resolve it.

Q. What is a vanilla compatible system ?
Ans. A vanilla compatible system is a computer capable of running OSx86 with minimal modifications (no patched kernel, compatible with Apple software updates). You have a vanilla capable system if: you have a Core 2 based processor.

Q. What is EFI emulation ?

Ans. EFI is the Extensible Firmware interface found in real macs. EFI is basically the “BIOS” of a Mac. For a computer to be properly recognized as a mac and to have the most compatibility it must have EFI. The problem here is that PCs do not have EFI.Developers have counteracted this problem by using EFI emulation which enables basic EFI function calls through a specially modified bootloader. EFI distributions for OSx86 include PC_EFI and Chameleon. Nearly all OSx86 installs have some form of EFI emulation installed, so this is not necessarily something to worry about. EFI emulation is required to use vanilla (unpatched) kernels and kexts, and to use GUID partition maps and EFI strings (more on that below)
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