Abyss installed to the hard drive...

The load times were GONE, but it kept crashing on transitions from one area to the next, or to the battle screen.  I should have done my research first, it looks like I need to enable compatibility mode 1.  I feel like I should do some playtesting to see if it works, but that data originally came from the epic PS2HD.com compatibility list that died a while back and they've never failed me before.

There's also a note saying "Use MDMA0 to avoid freezing".  This is interesting because I'd left the ToxicOS HDD mode option set to Default and almost everything's worked fine.  This might fix some of my issues with Guitar Hero crashing when loaded off of the HDD.  Compatibility Mode 1 slows down HDD access (I believe to the speed of the optical drive), since some games have issues if they get their data too quickly (lol wut).  MDMA0 is a hard drive mode that has a transfer speed of 4.2MB/sec.  I'm not sure how exactly Mode 1 and MDMA0 will interact, it seems kind of redundant to me. I'm unable to find anything stating what mode is used if the setting is left at Default, but I can guess that it's probably the fastest mode the drive supports, which is UDMA5 for my Maxtor drive.

It's always irritated me that lists of games that say "enable mode 3" or whatever are prevalent, but what exactly the modes do isn't really widespread.  After doing some research, Modes 1-3 are consistently the same thing through all the various HD loading methods.

• Mode 1, as previously mentioned, slows down HDD access.
• Mode 2 disables DVD9 (dual-layer DVD) support.  Very few games need this mode.
• Mode 3 makes the bootloader (in my case, ToxicOS) unload itself from memory after it launches the game.

ToxicOS has a mode 4, but I'm unsure what it does.  I know of a game it fixes though.  War of the Monsters can be played in one or two player modes using ToxicOS Mode 4 (without it, you must play with $player_count + $cpu_count >= 3 or it will crash).

Mode 3 is the most commonly required mode, followed by Mode 1.  Some games take Mode 1 and Mode 3.  Very few need Mode 2, and I believe a mere handful need ToxicOS' Mode 4.  The vast majority of games can be run without any modes at all.