Scanning and Rebuilding CHDs

Two "MAME CHDs (Merged)" dat-files are provided. A table with their differences follows:

Notes

(1) Because there isn't information about parent-clone relationships, the Merging Mode can't be selected on clrmamepro's scanner.

(2) The MAME emulator checks only the 'internal' hash (size isn't checked) of CHDs before starting emulation, because there can be two or more CHD files with the same 'internal' hash but with different 'external' hashes and sizes. Read DIF File for more information.

(3) CHDs in 'rom' XML tags makes clrmamepro 'think' those are regular (non-CHD) files, and because of that the 'CHDs' option can't be selected on clrmamepro's scanner.

Examples
Below are the hashes of the Area 51 CHD as reported by different sources:


 * According to CHDMAN ('internal' hash):

Input file:  area51.chd File Version: 5 Logical size: 1,281,982,464 bytes Hunk Size:   4,096 bytes Total Hunks: 312,984 Unit Size:   512 bytes Total Units: 2,503,872 Compression: lzma (LZMA), zlib (Deflate), huff (Huffman), flac (FLAC) CHD size:    497,632,790 bytes Ratio:       38.8% SHA1:        3b303bc37e206a6d7339352c869f050d04186f11 Data SHA1:   9ea749404c9a5d44f407cdb8803293ec0d61410d Metadata:    Tag='GDDD'  Index=0  Length=35 bytes CYLS:2484,HEADS:16,SECS:63,BPS:512.


 * According to the regular (XML) dat-file ('internal' hash):

Area 51 (R3000) 1996 	 Atari Games < disk name="area51" sha1=" 3b303bc37e206a6d7339352c869f050d04186f11 "/>


 * According to the Dir2Dat dat-file ('external' hash):

area51 < rom name="area51.chd" size ="497632790" crc="fe0e16af" sha1=" 86b126ee2d613d7e3ba5b12886962ccfbc8817e2 "/> 


 * According to How to hash a file with clrmamepro guide ('external' hash):

Name:	area51.chd Size:	497632790 CRC32:	fe0e16af MD5:	19ffdd41d0a05e882a6b08638f4c17ac SHA1:	 86b126ee2d613d7e3ba5b12886962ccfbc8817e2