New boot mechanism: load sector 0 to 0x800 and execute it

boot.asm

@@ -1,24 +1,15 @@
 ; disk booting routines
 ; these are only used during booting, they are not exposed via the jump table
 
-const KERNEL_FILE_STRUCT: 0x01FFF800 ; kernel.bin file struct is right above the system stack
+; load the boot sector of disk 0 to 0x00000800 and jump to it
-kernel_file_name: data.str "system  bin" data.8 0
-
-; read disk 0 and attempt to figure out what type of disk it is, and load the correct binary into memory
 ; inputs:
-; r0: disk size (bytes)
+; none
 ; outputs:
 ; none (doesn't return)
 start_boot_process:
-    ; r0 contains the size of the disk in bytes
-    ; divide the size by 512 and add 1 to get the size in sectors
-    div r0, 512
-    inc r0
-    mov r31, r0
-
     mov r0, BACKGROUND_COLOR
     call fill_background
-draw_boot_text:
+
     mov r0, boot_str
     mov r1, 16
     mov r2, 464
@@ -29,64 +20,16 @@ draw_boot_text:
     mov r12, FOX32ROM_VERSION_PATCH
     call draw_format_str_to_background
 
-    mov r0, 0          ; sector counter
+    mov r0, 0x80003000 ; command to read a sector from disk 0 into memory
-    mov r2, 0x00000800 ; destination pointer
+    mov r1, 0x80002000 ; command to set the location of the buffer
-    mov r3, 0x80003000 ; command to read a sector from disk 0 into memory
-    mov r4, 0x80002000 ; command to set the location of the buffer
 
-    ; first, check to see if this is a FAT-formatted disk or RYFS-formatted disk
+    ; read sector 0 to 0x800
-    out r4, r2         ; set the memory buffer location
+    out r1, 0x00000800
-    out r3, 0          ; read sector 0 into the buffer
+    out r0, 0
-    cmp.8 [r2], 0xEB   ; check for an x86 jmp instruction, indicating a possible FAT volume
-    ifz jmp start_boot_process_fat
-    cmp.8 [r2], 0xE9   ; check for an x86 jmp instruction, indicating a possible FAT volume
-    ifz jmp start_boot_process_fat
-    out r3, 1          ; read sector 1 into the buffer
-    add r2, 2
-    cmp.16 [r2], 0x5952 ; check for RYFS magic bytes
-    ifz jmp start_boot_process_ryfs
-    sub r2, 2
-start_boot_process_raw_binary_sector_loop:
-    out r4, r2         ; set the memory buffer location
-    out r3, r0         ; read the current sector into memory
-    inc r0             ; increment sector counter
-    add r2, 512        ; increment the destination pointer
-    loop start_boot_process_raw_binary_sector_loop
-    jmp start_boot_process_done
-start_boot_process_fat:
-    jmp start_boot_process_fat
-start_boot_process_ryfs:
-    ; open system.bin
-    mov r0, kernel_file_name
-    mov r1, 0
-    mov r2, KERNEL_FILE_STRUCT
-    call ryfs_open
-    cmp r0, 0
-    ifz jmp start_boot_process_error
 
-    mov r0, KERNEL_FILE_STRUCT
-    mov r1, 0x00000800
-    call ryfs_read_whole_file
-start_boot_process_done:
-    ; done loading !!!
     ; now clean up and jump to the loaded binary
     call boot_cleanup
     jmp 0x00000800
-start_boot_process_error:
-    mov r0, BACKGROUND_COLOR
-    call fill_background
-
-    mov r0, boot_error_str
-    mov r1, 16
-    mov r2, 464
-    mov r3, TEXT_COLOR
-    mov r4, 0x00000000
-    mov r10, FOX32ROM_VERSION_MAJOR
-    mov r11, FOX32ROM_VERSION_MINOR
-    mov r12, FOX32ROM_VERSION_PATCH
-    call draw_format_str_to_background
-
-    ret
 
 ; clean up the system's state before jumping to the loaded binary
 ; inputs:

main.asm

@@ -322,7 +322,6 @@ const MENU_FRAMEBUFFER:     0x0215618E ; max 640x480x4 = end address at 0x022821
 
 startup_str: data.str "fox32 - ROM version %u.%u.%u - insert boot disk - F12 for monitor" data.8 0
 boot_str: data.str "fox32 - ROM version %u.%u.%u - booting..." data.8 0
-boot_error_str: data.str "fox32 - ROM version %u.%u.%u - system.bin not found! - F12 for monitor" data.8 0
 
 menu_items_root:
     data.8 1                                                      ; number of menus