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AH = EFh
Return:
DL = video adapter type 00h original Hercules 01h Hercules Plus (port 03BAh reads x001xxxxx) 02h Hercules InColor (port 03BAh reads x101xxxxx) FFh not a Hercules-compatible card (port 03BAh bit 7 not pulsing) DH = memory mode byte 00h "half" mode 01h "full" mode FFh not a Hercules-compatible card
Program: MSHERC.COM/QBHERC.COM is a support program for the Microsoft Quick languages which makes their graphics libraries compatible with a Hercules card by adding video modes 08h and 88h, and supporting text in the new graphics modes.
Notes: While in mode 08h or 88h, INT 10 supports the Hercules card much like a CGA.. MSHERC performs an installation check by setting DL=FFh and testing whether it has been changed on return, which causes it to reinstall itself when no HGC is present (or HGC emulation has temporarily been disabled); a better installation check would be to use DX=80FFh and check whether DX has been changed. Reportedly returns DH=00h on some not-entirely-Hercules-compatible cards
Index:
Installation check;MSHERC
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