Some 90k 8c still contain the 2.20 BIOS.
@noise: If FMCB doesn´t work Memento/Memor32 won´t also, because both rely on the OSD-Upgrade-Feature (which has been disabled in BIOS 2.30. Even thought the function is still there, it is simply not called.).
Beside that FMCB+ESR has a better compatibility, than Memento.
I would even say, that Memento doesn´t have a complete system-initialisation (which FMCB since 1.8 [hopefully complete] has).
About the ESR-Question.
If you have a way to run Homebrew (i.e. AR MAX and X-Mas 2k8-Loader), you can try the ESR-GUI.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux