PSF is the Linux standard font format, but various old and very obsolete formats still exist.
CP font files are just fragments of CPI fonts, obtained by concatenating
CPEntryHeader (28 bytes), FontDataHeader (6 bytes),
and for each font ScreenFontHeader (6 bytes) and
ScreenFontData, that is, the part of a CPI font describing
one code page.
(History: the first .cp files used with Linux that I know of
were 972.cp and 880.cp included in
codepage.tar.gz