Update format script

I think there may still be some issues with a drive that is formatted
wrong, but it works consistently right now.

When modifying the boot sector, it now leaves alone the partition tables
and the bios parameter block. This does reduce the amount of code from
510 bytes to 380, but this is find as it only takes about 29 bytes to
load a sector into memory.

sw/bios/bootloader.s

@@ -1,4 +1,4 @@
-.importzp sp, ptr1, ptr2, ptr3, ptr4, tmp1, tmp2, tmp3
+.importzp sp, ptr1, ptr2, ptr3, ptr4, tmp1, tmp2, tmp3, sreg
 
 .autoimport on
 
@@ -11,6 +11,10 @@ _console_read_char      = $2
 _console_write_char     = $4
 _sd_readblock           = $6
 
+buf  = $8200
+addrh = $0000
+addrl = $0001
+
 .segment "BOOTSECTOR"
 
 _start:
@@ -18,10 +22,35 @@ _start:
 
 .byte "SUPR6502"
 
+_preamble:
+
+.res (11+_start-_preamble)
+
+_bpb: .res 60
+
 _main:
         lda #<str
         ldx #>str
         jsr _cputs
+
+        lda #<addrh
+        sta sreg
+        lda #>addrh
+        sta sreg + 1
+        lda #<addrl
+        ldx #>addrl
+        jsr pusheax
+        lda #<buf
+        ldx #>buf
+        jsr pushax
+        lda #<ptr1
+        ldx #>ptr1
+        jsr _SD_readSingleBlock
+        
+        lda #<buf
+        ldx #>buf
+        jsr _SD_printBuf
+
 @end:   bra @end
 
 
@@ -29,7 +58,9 @@ str: .asciiz "Hello from the bootloader!\r\n"
 
 _end:
 
-.res (446+_start-_end)
+.res (440+_start-_end)
+
+.res 6
 
 .res 16
 .res 16