Just wanted to say thanks for taking the time to actually figure this one out. Tony H, looking forward to the finished result.
No problem. The 2x walking speed hack seems to work very well. The 3x and 4x speed hacks had some problems, so won't post those.
Here's how to hack your ROM to walk twice as fast...
Open up your Phantasy Star 3 ROM with a hex editor and make these changes:
At ROM address $0002D0, change the D258 to 6032. This causes the game to completely skip the whole checksum process (no red screen). This also makes the game load faster.
At ROM address $002E1D, change the 01 to 02. This determines how fast the "screen" will move.
At ROM address $004E4D, change the FF to FE. This is your speed when walking Left.
At ROM address $004E4E, change the 01 to 02. This is your speed when walking Right.
At ROM address $004E51, change the 01 to 02. This is your speed when walking up.
At ROM address $004E52, change the FF to FE. This is your speed when walking Down.
Save those changes and you're all set. Just remember that any save states/save games made BEFORE you hacked your ROM will need to use one of the PAR codes below. However, any save states made after the hack should work fine without the extra PAR code. If you're using an old save state/save game, make sure you turn the PAR code on BEFORE you load your saved game!
Here are the Game Genie codes for walking twice as fast (in case you don't want to hack your ROM).
Master code (improved). Only use if you get a blank/red screen. This code
also makes the game load faster.
Makes your character walk twice as fast.
Some notes about these codes...
These codes must be turned on before the game starts.
If you're starting a new game, make sure you have all the codes turned on before
you pick your message scrolling speed.
If you're using the codes with an emulator save state, you'll need to add one
of these PAR codes as well:
FFD242:0002 (use this code with Gens emulator).
FFD243:0002 (use this code with Kega Fusion emulator).
Make sure you have all the codes turned on BEFORE you load your save state!