diff --git a/CMakeLists.txt b/CMakeLists.txt
index 397b925c..8f522402 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,10 @@ set(CMAKE_FIND_ROOT_PATH ${LUNA_ROOT}/toolchain/x86-64-luna)
 
 set(ARCH $ENV{ARCH})
 
+if(NOT DEFINED $ENV{ARCH})
+set(ARCH "x86_64")
+endif()
+
 message(STATUS "Configuring Luna for ${ARCH}")
 
 add_subdirectory(luna)
diff --git a/kernel/src/arch/MMU.h b/kernel/src/arch/MMU.h
index f18e0302..095ed40a 100644
--- a/kernel/src/arch/MMU.h
+++ b/kernel/src/arch/MMU.h
@@ -1,9 +1,11 @@
 #pragma once
 #include <luna/Result.h>
 
-struct PageDirectory;
-
-extern const usize ARCH_PAGE_SIZE;
+#ifdef ARCH_X86_64
+#include "arch/x86_64/MMU.h"
+#else
+#error "Unknown architecture."
+#endif
 
 namespace MMU
 {
diff --git a/kernel/src/arch/Timer.cpp b/kernel/src/arch/Timer.cpp
index 26515c99..7f29500b 100644
--- a/kernel/src/arch/Timer.cpp
+++ b/kernel/src/arch/Timer.cpp
@@ -73,9 +73,9 @@ namespace Timer
     usize ticks_us() // We want a bit of precision; if there are 10 ticks/ms, do not return the truncated ms value *
                      // 1000, but ticks * 100 (1000/10), which is more precise
     {
-        if (ARCH_TIMER_FREQ > 1000) [[unlikely]]
-            return timer_ticks / (ARCH_TIMER_FREQ / 1000);
-        return timer_ticks * (1000 / ARCH_TIMER_FREQ);
+        if constexpr (ARCH_TIMER_FREQ > 1000) return timer_ticks / (ARCH_TIMER_FREQ / 1000);
+        else
+            return timer_ticks * (1000 / ARCH_TIMER_FREQ);
     }
 
     usize ticks_ns()
diff --git a/kernel/src/arch/Timer.h b/kernel/src/arch/Timer.h
index 21c389d7..c540631b 100644
--- a/kernel/src/arch/Timer.h
+++ b/kernel/src/arch/Timer.h
@@ -1,7 +1,11 @@
 #pragma once
 #include <luna/Types.h>
 
-extern const usize ARCH_TIMER_FREQ; // How many timer ticks in one millisecond?
+#ifdef ARCH_X86_64
+#include "arch/x86_64/Timer.h"
+#else
+#error "Unknown architecture."
+#endif
 
 static const usize MS_PER_SECOND = 1000;
 static const usize US_PER_SECOND = MS_PER_SECOND * 1000;
diff --git a/kernel/src/arch/x86_64/MMU.cpp b/kernel/src/arch/x86_64/MMU.cpp
index fa09ff14..d4088c1f 100644
--- a/kernel/src/arch/x86_64/MMU.cpp
+++ b/kernel/src/arch/x86_64/MMU.cpp
@@ -3,41 +3,6 @@
 #include <luna/String.h>
 #include <luna/SystemError.h>
 
-#define PAGE_SIZE 4096
-
-const usize ARCH_PAGE_SIZE = PAGE_SIZE;
-
-const u64 rindex = 0776;          // recursive index
-const u64 sign = 0177777UL << 48; // sign extension
-
-struct [[gnu::packed]] PageTableEntry
-{
-    union {
-        struct [[gnu::packed]]
-        {
-            bool present : 1;
-            bool read_write : 1;
-            bool user : 1;
-            bool write_through : 1;
-            bool cache_disabled : 1;
-            bool accessed : 1;
-            bool ignore0 : 1;
-            bool larger_pages : 1;
-            bool ignore1 : 1;
-            u8 available : 3;
-            u64 address : 48;
-            u8 available2 : 3;
-            bool no_execute : 1;
-        };
-        u64 raw;
-    };
-
-    void set_address(u64 addr);
-    u64 get_address() const;
-
-    void clear();
-};
-
 #pragma GCC push_options
 #pragma GCC diagnostic ignored "-Wconversion"
 
@@ -58,14 +23,6 @@ void PageTableEntry::clear()
     raw = 0;
 }
 
-struct alignas(PAGE_SIZE) PageDirectory
-{
-    PageTableEntry entries[512];
-};
-
-static_assert(sizeof(PageTableEntry) == 8UL);
-static_assert(sizeof(PageDirectory) == PAGE_SIZE);
-
 namespace MMU
 {
 
@@ -213,7 +170,7 @@ namespace MMU
             u64 addr = TRY(MemoryManager::alloc_frame());
             l4.present = true;
             l4.set_address(addr);
-            memset(l3_table(virt), 0, PAGE_SIZE);
+            memset(l3_table(virt), 0, ARCH_PAGE_SIZE);
             l4.ignore0 = l4.ignore1 = 0;
         }
         if (flags & Flags::ReadWrite) l4.read_write = true;
@@ -225,7 +182,7 @@ namespace MMU
             u64 addr = TRY(MemoryManager::alloc_frame());
             l3.present = true;
             l3.set_address(addr);
-            memset(l2_table(virt), 0, PAGE_SIZE);
+            memset(l2_table(virt), 0, ARCH_PAGE_SIZE);
             l3.ignore0 = l3.ignore1 = 0;
         }
         if (flags & Flags::ReadWrite) l3.read_write = true;
@@ -239,7 +196,7 @@ namespace MMU
             u64 addr = TRY(MemoryManager::alloc_frame());
             l2.present = true;
             l2.set_address(addr);
-            memset(l1_table(virt), 0, PAGE_SIZE);
+            memset(l1_table(virt), 0, ARCH_PAGE_SIZE);
             l2.ignore0 = l2.ignore1 = 0;
         }
         if (flags & Flags::ReadWrite) l2.read_write = true;
diff --git a/kernel/src/arch/x86_64/MMU.h b/kernel/src/arch/x86_64/MMU.h
new file mode 100644
index 00000000..0ebc7978
--- /dev/null
+++ b/kernel/src/arch/x86_64/MMU.h
@@ -0,0 +1,43 @@
+#pragma once
+#include <luna/Types.h>
+
+const usize ARCH_PAGE_SIZE = 4096;
+
+const u64 rindex = 0776;          // recursive index
+const u64 sign = 0177777UL << 48; // sign extension
+
+struct [[gnu::packed]] PageTableEntry
+{
+    union {
+        struct [[gnu::packed]]
+        {
+            bool present : 1;
+            bool read_write : 1;
+            bool user : 1;
+            bool write_through : 1;
+            bool cache_disabled : 1;
+            bool accessed : 1;
+            bool ignore0 : 1;
+            bool larger_pages : 1;
+            bool ignore1 : 1;
+            u8 available : 3;
+            u64 address : 48;
+            u8 available2 : 3;
+            bool no_execute : 1;
+        };
+        u64 raw;
+    };
+
+    void set_address(u64 addr);
+    u64 get_address() const;
+
+    void clear();
+};
+
+struct alignas(ARCH_PAGE_SIZE) PageDirectory
+{
+    PageTableEntry entries[512];
+};
+
+static_assert(sizeof(PageTableEntry) == 8UL);
+static_assert(sizeof(PageDirectory) == ARCH_PAGE_SIZE);
\ No newline at end of file
diff --git a/kernel/src/arch/x86_64/Timer.cpp b/kernel/src/arch/x86_64/Timer.cpp
index 9add861b..c35a4cf5 100644
--- a/kernel/src/arch/x86_64/Timer.cpp
+++ b/kernel/src/arch/x86_64/Timer.cpp
@@ -4,7 +4,6 @@
 #define PIT_CHANNEL_0 0x40
 
 const u64 base_frequency = 1193182;
-const usize ARCH_TIMER_FREQ = 5;
 
 void Timer::arch_init()
 {
diff --git a/kernel/src/arch/x86_64/Timer.h b/kernel/src/arch/x86_64/Timer.h
new file mode 100644
index 00000000..1a0e474b
--- /dev/null
+++ b/kernel/src/arch/x86_64/Timer.h
@@ -0,0 +1,4 @@
+#pragma once
+#include <luna/Types.h>
+
+const usize ARCH_TIMER_FREQ = 5;
\ No newline at end of file
diff --git a/luna/CMakeLists.txt b/luna/CMakeLists.txt
index 1ac0c37f..8cb8b56b 100644
--- a/luna/CMakeLists.txt
+++ b/luna/CMakeLists.txt
@@ -24,11 +24,6 @@ target_compile_options(luna-freestanding PRIVATE -fno-rtti -ffreestanding -fno-e
 target_compile_options(luna-freestanding PRIVATE -fno-asynchronous-unwind-tables -fno-omit-frame-pointer)
 target_compile_options(luna-freestanding PRIVATE -nostdlib -mcmodel=kernel)
 
-if("${ARCH}" MATCHES "x86_64")
-target_compile_options(luna-freestanding PRIVATE -mno-red-zone)
-target_compile_options(luna-freestanding PRIVATE -mno-80387 -mno-mmx -mno-sse -mno-sse2)
-endif()
-
 target_include_directories(luna-freestanding PUBLIC include/)
 set_target_properties(luna-freestanding PROPERTIES CXX_STANDARD 20)
 
@@ -39,4 +34,11 @@ target_compile_options(luna PRIVATE -Wmissing-include-dirs -Wswitch-default -Wca
 target_compile_options(luna PRIVATE -Wcast-align -Wwrite-strings -Wlogical-op -Wredundant-decls -Wshadow -Wconversion)
 target_compile_options(luna PRIVATE -fno-asynchronous-unwind-tables -fno-omit-frame-pointer)
 target_include_directories(luna PUBLIC include/)
-set_target_properties(luna PROPERTIES CXX_STANDARD 20)
\ No newline at end of file
+set_target_properties(luna PROPERTIES CXX_STANDARD 20)
+
+if("${ARCH}" MATCHES "x86_64")
+target_compile_options(luna-freestanding PRIVATE -mno-red-zone)
+target_compile_options(luna-freestanding PRIVATE -mno-80387 -mno-mmx -mno-sse -mno-sse2)
+target_compile_definitions(luna-freestanding PUBLIC ARCH_X86_64)
+target_compile_definitions(luna PUBLIC ARCH_X86_64)
+endif()
\ No newline at end of file