Editing Commodore 1581 (section)

== Specifications ==
{| class=wikitable
! Quantity !! Value
|-
| Onboard CPU    || [[MOS Technology 6502]] @ 2 [[Hertz|MHz]]
|-
| RAM            || 8 [[kilobyte|kB]]{{r|z81sv02|page=2}}
|-
| ROM            || 32 kB{{r|z81sv02|page=2}}
|-
| Disk controller || [[Western Digital FD1771|WD1770]]{{r|w81}}{{r|z81sv02|page=2, 12}} or WD1772{{r|1987_LtKernal}}
|-
| Communications controller || [[MOS Technology 8520|MOS Technology 8520A]]<ref name=z81sv02/>
|-
| Transfer protocols || Standard and fast serial; [[Burst mode (computing)|burst mode]]; and commands for parallel interface (the latter not used)
|-
| Disk type      || 3.5" inch
|-
| Storage format || [[Modified Frequency Modulation|MFM]], [[double density]], [[Double-sided disk|double-sided]]
|-
| Interface      || [[Commodore bus|CBM's proprietary serial IEEE-488]]
|-
| Power          || {{nowrap|5 V @ 1 A}} {{nowrap|(5 [[Volt-ampere|VA]])}}<br> {{nowrap|12 V @ 0.5 A}} {{nowrap|(6 VA)}}
|}

=== 1581 Image Layout ===
The 1581 disk has 80 logical tracks, each with 40 logical sectors (the actual physical layout of the diskette is abstracted and managed by a hardware translation layer).  The directory starts on 40/3 (track 40, sector 3).  The disk header is on 40/0, and the BAM (block availability map) resides on 40/1 and 40/2.

Header Contents

 $00–01 T/S reference to first directory sector (40/3)
     02 DOS version ('D')
  04-13 Disk Label, $A0 padded
  16-17 Disk ID
  19-1A DOS type ('3D')

BAM Contents, 40/1

 $00–01 T/S to next BAM sector (40/2)
     02 DOS version ('D')
  04-05 Disk ID
     06 I/O byte
     07 Autoboot flag
  10-FF BAM entries for Tracks 1–40

BAM Contents, 40/2

 $00–01 00/FF
     02 DOS version ('D')
  04-05 Disk ID
     06 I/O byte
     07 Autoboot flag
  10-FF BAM entries for Tracks 41–80