.SID File Format – Versions

Commodore 64 SID tune

The version is the big-endian word at +04. Each version keeps everything of the one before and adds to it, so a reader that knows version 5 reads every file. The format document (SID_file_format.txt, last updated 9 October 2026) describes them together; this page separates them. The names “PSID v2NG” (“next generation”) and “RSID” belong to version 2 and later: a version 2 file can be an old PlaySID file or a v2NG one, and nothing in the header tells them apart except the flag bits that old players ignored.

What each version added

VersionHeader sizeData offsetAdded
1118 bytes ($76)$0076The magic PSID, the data offset, the load, init and play addresses, the number of songs, the start song, the speed word, and the three 32-byte strings. No flags: every tune is for a PAL or NTSC machine and the SID model are not stated.
2124 bytes ($7C)$007CThe flags word (built-in or MUS player, PlaySID-specific, video clock, SID model), the start page and page length of free memory, and two bytes that must be 0. PSID v2NG and RSID are version 2 and later: RSID (the magic RSID) is for tunes that need a real C64 environment.
3124 bytes$007CThe second SID: its address at +7A and its model in flag bits 6 and 7.
4124 bytes$007CThe third SID: its address at +7B and its model in flag bits 8 and 9.
5124 bytes$007CUp to 15 SID chips through an address configuration (+7A and +7B mean something else), stereo panning (flag bits 6 to 9 mean something else), the three strings as one 96-byte run of null-terminated strings, an optional song length table after the data (flag bit 10), and the FM OPL flag (bit 11).

RSID is valid only from version 2: its load address, play address and speed must be 0. A header with a version outside 1 to 5, or with the magic neither PSID nor RSID, is not a SID file.

Telling them apart

  1. Read the magic: PSID or RSID.
  2. Read the version word at +04. 1 means the 118-byte header with no flags. The data offset at +06 repeats this: $0076 for version 1, $007C for the rest.
  3. For version 3 and 4 the bytes at +7A and +7B are SID addresses ($42 to $7E, $E0 to $FE, even); for version 5 they are the multi-SID configuration (bits 0 to 3 the number of chips, bits 4 to 7 the address configuration) and the start of the second SID.
  4. For version 5, the flag word’s bits 6 to 9 are the panning, not SID models, and bit 10 says a length table follows.

Fields that an older version does not have are reserved in the newer layout: a version 2 file must have 0 at +7A and +7B, a version 3 file 0 at +7B, and a version 3 file’s flag bits 8 and 9 are 0. The explorer notes each of these when it finds them set.

Examples from real files

Version 2: Rob Hubbard’s “Commando” from the HVSC. The load address in the header is 0, so the first two bytes of the data (00 50, little-endian $5000) give it. Init is $5FB2, play $5012, 19 songs, start song 1; the speed word is 0, so every song is called by the vertical blank. The flags are $0014: the built-in player, C64 compatible, PAL, a MOS 6581.

00000000  50 53 49 44 00 02 00 7C  00 00 5F B2 50 12 00 13  PSID..|.._.P...
00000010  00 01 00 00 00 00 43 6F  6D 6D 61 6E 64 6F 00 00  ......Commando..
00000070  00 00 00 00 00 00 00 14 00 00 00 00 00 50  .............P
Version 2: the magic, the version, the data offset $007C, the addresses, the songs and start song, the speed, the name; then at +76 the flags $0014, start page 0, page length 0, two reserved bytes, and the data

Version 3: “Mega Power Man” by Owen Crowley has a second SID. The byte at +7A is $42, so the second chip is at $D420; the flags are $00A4 (PAL, MOS 8580, and an 8580 for the second chip too). Version 4: “A Walk in the Countryside” by Gaetano Chiummo has three: +7A is $42 and +7B is $44 ($D420 and $D440), flags $02A4.

00000070  00 00 00 00 00 00 00 A4 00 00 42 00 00 10  ...........B...
00000070  00 00 00 00 00 00 02 A4 00 00 42 44 00 10  ...........BD..
The end of the header of a version 3 file (top) and a version 4 file (bottom): the flags, the free pages, then the second and third SID address bytes

Version 1 has no flags: the data (and in a typical file, the two-byte load address) starts at +76. Version 5 files are written by new tools; the format document’s own example gives the song lengths of Rob Hubbard’s “Human Race” as 02 44 05 54 - 01 16 08 10 … (2:44.554, 1:16.810 …) at the end of such a file.

RSID against PSID

RSID is PSID v2NG with limits: the version is 2 to 5, the load address, play address and speed are 0, and the effective load address is at least $07E8. A PSID tune is called by the player through its play address; an RSID tune is started once and sets up its own interrupts. See C64 environment for what each gets before it starts, and flags for bit 1 (PlaySID-specific for a PSID file, C64 BASIC for an RSID one).