Format:SNA snapshot file format - Revision history

ColinPitrat at 15:30, 9 March 2025

2025-03-09T15:30:17Z

2022-08-07T10:00:30Z

cleanup example of RLE compression

2014-08-23T14:15:12Z

‎Memory

2014-08-21T08:29:44Z

‎Memory block chunks (CPC/Plus/KC Compact/Aleste)

2014-08-21T08:29:20Z

‎Limitations of this snapshot format

2014-08-21T08:28:09Z

‎CPC+ Chunk

2014-08-21T08:27:54Z

‎Memory block chunks

2014-08-21T08:27:26Z

‎Memory

2014-08-21T08:26:50Z

‎Memory block chunks

2014-08-21T08:15:38Z

‎CPC+ Chunk

@@ Line 719: / Line 719: @@
 * The snapshot format doesn't support additional hardware. A basic CPC464, CPC664, CPC6128 system is assumed.
 * The snapshot format doesn't support KC Compact or Aleste hardware.
-* The snapshot doesn't have knowledge of which ROMs are in use. This means it doesn't know which OS, BASIC or AMSDOS ROM, and nothing about expansion roms.
+* The snapshot doesn't have knowledge of which ROMs are in use. This means it doesn't know which OS, BASIC or AMSDOS ROM, and nothing about expansion roms. On Plus range, it doesn't know which Cartridge is loaded.
 The format generally assumes a base CPC6128/6128Plus system with no attached hardware except for up to 512K of dk'tronics compatible RAM.

@@ Line 681: / Line 681: @@
 i.e. <control byte>, <count>, <byte>
-Examples:
+Examples (Uncompressed = Compressed):
+* 11 22 33 = 11 22 33
-Uncompressed = Compressed
+* E5 03 11 = 11 11 11
-22 33 = 11 22 33
+* E5 00 = E5
 E5 03 11 = 11 11 11
 E5 00 = E5
 === Breakpoint chunk (Winape emulator specific) ===

@@ Line 687: / Line 687: @@
 E5 03 11 = 11 11 11
 E5 00 = E5
 == Memory ==

@@ Line 652: / Line 652: @@
 |}
-== Memory block chunks (CPC/Plus/KC Compact/Aleste) ==
+=== Memory block chunks (CPC/Plus/KC Compact/Aleste) ===
 There may be 1 or more of these memory blocks.

@@ Line 703: / Line 703: @@
 * The snapshot format doesn't support KC Compact or Aleste hardware.
 * The snapshot doesn't have knowledge of which ROMs are in use. This means it doesn't know which OS, BASIC or AMSDOS ROM, and nothing about expansion roms.
-It generally assumes a CPC6128/6128Plus system with ram expanded up to 512K.

@@ Line 451: / Line 451: @@
 == V3 Chunks ==
-=== CPC+ Chunk  ===
+=== CPC+ Chunk (Plus only) ===
 Chunk name: "CPC+"

@@ Line 690: / Line 690: @@
 == Memory ==
-Uncompressed snapshot allows sizes of:
+Uncompressed memory described by the snapshot allows sizes of:
 * 64K (base 64K only),
 * 128K (base 64K + 64K dk'tronics compatible RAM expansion using ram selections C4-C7),

@@ Line 654: / Line 654: @@
 == Memory block chunks ==
-Chunk name: MEM0..MEM8. 64K is stored per block.
+There may be 1 or more of these memory blocks.
-MEM0 for Standard 64k.
+Chunk name: MEM0..MEM8.
-MEM1 to MEM8 for memory expansion bank.
-If a chunk exists for that block, this means the memory is stored compressed.
+Each block represents 64K.
-It is possible to have a snapshot with 64KB base ram uncompressed and additional banks compressed, but it's advised to either use MEM chunks or store the memory uncompressed in the V2 style.
+MEM0 describes the standard on-board 64k.
 A RLE compression is used with 0x0e5 as the control byte.
-Example:
+i.e. <control byte>, <count>, <byte>
 22 33 = 11 22 33
 E5 03 11 = 11 11 11

@@ Line 448: / Line 448: @@
 The following chunks are currently defined:
 === CPC+ Chunk  ===
 Chunk name: "CPC+"
 Chunk data: