Partial PS2 BC on Non-BC Fat PS3s!
It seems that Sony was working on full PS2 emulation right up to FW 2.60, and this feature works in Non-BC PS3s in Service Mode! Apparently this ability was removed from FW 2.70 and above, but if you have a PS3 which came with FW 2.60 or below (most fat PS3s except for late models) it can be downgraded to use this feature.
PS3News poster "MODERNTHIS" posted this guide;
How to Play PS2 Games on a Non Backwards Compatible PS3!
Okay I came across this while downgrading to several PlayStation 3 firmwares, here is how to play PS2 Games on a non backwards compatible PS3 in six simple steps!
Step 1. Enter Service Mode.
Step 2. Downgrade your PS3 System to System Software Version 2.50 (this is the one that supports more PS2 gaming).
Step 3. After downgrading don't get out of service mode.
Step 4. Uncheck Game-auto start in System Settings.
Step 5. Insert your PS2 disk cd/dvd on PS3.
Step 6. Load it and do not press the PS Button while playing otherwise it will crash.
Tested on a CECHP01 Console. The one game that would play exactly like in a PS2 was Twisted Metal Black.
Note: DO NOT TRY THIS ON A PS3 SLIM IT BRICKS! (But can be recovered while in service mode) This can only be done on a PS3 System bought 11/20/2008 80 GB PS3 12/31/2008 160 GB Uncharted Bundle (With Pain Voucher)
Cheers and happy playing.
This was later confirmed by poster "joffe"
It indeed works also on CECHK04 with FW2.50 and FW2.60 in service mode, FW2.70 complains about 'non bc-compatible titles'
Knight Rider (CD-ROM/PAL) works laggy, about 60% original speed.
Oni (CD-ROM/PAL) works maybe a bit laggy
ProRally 2002 (CD-ROM/PAL) works OK, some [accept/cancel] icons for name and country selection seem to be off-screen
CD-ROM games (blue CD icon) seem to work, DVD-ROM games (golden CD icon) crash after loading and some seeking, hard-off is needed to reboot.
CD-ROM games exit fine to XMB after pressing PS for >3s.
Tests were done on composite video out.
Obviously $ony planned full-SW emulation to get rid of EE but skipped it between 2.60 and 2.70
Poster "Mad Lion" remembered this old YouTube video from the start of 2009 of someone stuck in Service Mode on a Non-BC 40GB PS3 demonstrating the ability to play PS2 games. Back then it was assumed to be fake, but now it seems that it was possibly for real.
[ame=http://www.youtube.com/watch?v=_0U7vElslY0]YouTube - Ps3 de 40 Gb funcionando con juegos de Ps2(FactoryMode)[/ame]