EMULAB Forum

clrmamepro [English] => clrmame Discussion => Topic started by: UnluckyForSome on 14 June 2018, 18:00

Title: What is CLRMAMEPRO doing when it “resizes” roms?
Post by: UnluckyForSome on 14 June 2018, 18:00

So recently I had to convert a bunch of TOSEC Dreamcast sets into The. ReDump standard using a tool I found online. Upon scanning with CLRMAMEPRO it alerted me that several of these converted files were the wrong size by a few bytes. I was just wondering why this would be and how (if the rom/iso is the wrong size) the size is changed without screwing up any of the precious data inside?

Thanks :-D

Title: Re: What is CLRMAMEPRO doing when it “resizes” roms?
Post by: Roman on 14 June 2018, 18:18

well, a wrong size is of course only fixable with a given hash for the correctly sized rom.

So assume you got a file with size 2kb and a hashvalue of let's say 0x12345678 and a given "right" size of 1kb. Now cmpro checks the first half of the 2kb file if it matches the checksum...or the 2nd half....or it starts to look at a block of 1kb size which matches the checksum etc...it does some checks like bitswaps, or fill with 0x00 / 0xff (when the right size should be bigger)....etc etc...some are done during the "fix checksum check (in combination with checksum analysis)...e.g. when the size is ok but the checksum is not

So it does not simply cut down the file ;-)

Title: Re: What is CLRMAMEPRO doing when it “resizes” roms?
Post by: UnluckyForSome on 14 June 2018, 20:31

Ahh I think I understand, clever stuff! Thanks for the explanation Roman :D