Mayumi V4 = SCPH-5xxx to scph-10x (Full Stealth, Not recommended for SCPH-102 PAL model. JPN consoles need the Import player swap disc for Import Games).
MM2 = SCPH-100x Series (Partial Stealth, Does not provide stealth on the SCPH-1000 PU-7 JPN board. Certain JPN boards may need the Import player swap disc for USA and PAL games).
Stealth 2.8a = SCPH 1000 JPN PU-7 Board  (Partial Stealth)
ONEChip = SCPH-102 (PAL). (Comes with some wire "NTSC Color FIX" for proper NTSC color display when using Composite/S-Video cables)

Please let me know which model and region your console is when ordering, so i have the right chip ready for your model and region (It's located on the bottom of the console).
i.e
SCPH-5500 NTSC-J
SCPH-7501 NTSC-U/C
SCPH-102 PAL