The Radeon R300 and R420 GPUs used an "fp24" floating-point format with 7 bits of exponent and 16 bits (+1 implicit) of mantissa.
ðə ɹˈeɪdiːˌɑːn ˈɑːɹ θɹˈiːhˈʌndɹɪd ænd ˈɑːɹ fˈoːɹhˈʌndɹɪd twˈɛnti dʒˌiːpˌiːjˈuːz jˈuːzd æn "ˌɛfpˈiː twˈɛnti fˈoːɹ" flˈoʊɾɪŋpˈɔɪnt fˈɔːɹmæt wɪð sˈɛvən bˈɪts ʌv ɛkspˈoʊnənt ænd sˈɪkstiːn bˈɪts plˈʌs wˈʌn ɪmplˈɪsɪt ʌv mæntˈɪsə.