SARCH:
Sub-architecture to build for. Right now you can only select xbox, which enables some code needed to run ROS on a XBox 1
OARCH:
Generate instructions for this CPU type. See CPU Type list below.
TUNE:
Which CPU ReactOS should be optimized for.  Specify one of the above CPUs or generic. When this option is not used, GCC will optimize for the processor specified by OARCH.See CPU Type list below.
OPTIMIZE:
What level of optimisation to use.
KDBG:
Whether to compile in the integrated kernel debugger.
DBG:
Whether to compile for debugging. No compiler optimizations will be performed.
GDB:
Whether to compile for debugging with GDB. If you don't use GDB, don't enable this.
NSWPAT:
Whether to compile apps/libs with features covered software patents or not. If you live in a country where software patents are valid/apply, don't enable this (except they/you purchased a license from the patent owner).
_WINKD_:
Whether to compile with the KD protocol. This will disable support for KDBG as well as rossym and symbol lookups, and allow WinDBG to connect to ReactOS. This is currently not fully working, and requires kdcom from Windows 2003 or TinyKRNL. Booting into debug mode with this flag enabled will result in a failure to enter GUI mode. Do not enable unless you know what you're doing.
_ELF_:
Whether to compile support for ELF files. Do not enable unless you know what you're doing.
BUILD_MP:
Whether to compile the multi processor versions for ntoskrnl and hal.


CPU Type List:

i386 Intel's i386 CPU. (No scheduling is implemented for this chip.)
i486 Intel's i486 CPU. (No scheduling is implemented for this chip.)
i586, pentium Intel Pentium CPU with no MMX support.
pentium-mmx Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
i686, pentiumpro Intel PentiumPro CPU.
pentium2 Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
pentium3, pentium3m Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set support.
pentium-m Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set support. Used by Centrino notebooks.
pentium4, pentium4m Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.
prescott Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction set support.
nocona Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and SSE3 instruction set support.
core2
Intel Dual Core CPU, MMX, SSE, SSE2 and SSE3 instruction set support.
k6 AMD K6 CPU with MMX instruction set support.
k6-2, k6-3 Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support.
athlon, athlon-tbird AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions support.
athlon-4, athlon-xp, athlon-mp Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE instruction set support.
k8, opteron, athlon64, athlon-fx AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)
opteron-sse3
AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, SSE3, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)
barcelona
AMD Multi Core CPU. MMX, SSE, SSE2, SSE3, 3dNOW!, enhanced 3dNOW! Support
geode
Low power version AMD CPU. MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! Support
winchip-c6 IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction set support.
winchip2 IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW! instruction set support.
c3
Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is implemented for this chip.)
c3-2
Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is implemented for this chip.)