Special boot-up key commands [NEC PC98]

Hold down a key showed in bellow table when you turn on the PC or reset it. Ten keys (numeric pad) doesn't work.

Key Function Notes
STOP Skip system memory test Undocumented
TAB Show Fixed Disk Boot menu With an extended formatted HD.
COPY Boot from RAM drive Only models with a RAM hard drive
SHIFT+STOP+CTRL Dump system memory into FD PC-9801VX and later, undocumented
CTRL+CAPS+カナ+GRPH Show CPU speed and screen mode PC9801RA and later, undocumented
CTRL+SHIFT Reset data in Memory switch Only laptop models, undocumented
GRPH+SHIFT Reset data in Memory switch PC-9801DA and later, undocumented
HELP Access to System Setup Menu PC-9801DA and later
HELP+RETURN Access to System Setup Menu Some machines come with CPU upgrade kit
GRPH+1 Set H-Freq of monitor-out to 24 kHz PC-9821 and later except model S1, S2
GRPH+2 Set H-Freq of monitor-out to 31 kHz PC-9821 and later except model S1, S2
HELP+ESC+1 Show BIOS revision PC-9821An and later, undocumented
HELP+ESC+5 Allow sending memory refresh to C-bus PC-9821 and later, undocumented
HELP+ESC+6 Stop sending memory refresh to C-bus PC-9821 and later, undocumented
HELP+ESC+8 Show BIOS Update Menu PC-9821 and later, undocumented
HELP+ESC+9 Init PnP (Plug and Play) BIOS PnP supported models, undocumented
CTRL Boot from FD in High Resolution mode (only specific models)
ESC Boot from drive number 00 in High Resolution mode (only specific models)
f1 - vf5 Boot from its drive number in High Resolution mode (only specific models)

Source: 第三研究所 第一電算機研究室 NEC PC-9800シリーズ、SV-98シリーズ裏コマンド一覧表 http://www.amy.hi-ho.ne.jp/nakajima-jr/com/appendix/uracom.htm