Sector 0 (256 byte) bootloader
 reads from track 4 (formatted with track80, 512 bytes/sec, sec numbering 48..41)
 
Track 5, Sector 0
  Start of Terminal code, same as s10.trm in cp/m
  Physical track 5 has logical track 82
  Last Track for terminal code: 8
Track 9, h0
  8 * 512. logical track 90, empty
Track 9, h1
  16 * 256 Bytes


Track 25, h0 .. Track 35
  8 * 512 Bytes, logical track 128, sectors 80..73
  start of bbm ? (S10-xxxxx)
  only head 0
  