Access to \device\physicalmemory

Originally Posted by souz

so, a get into ring0 by driver, (TVICHHW for Delphi) and trying to write into \\device\physicalmemory.... but exception Access violation popups....
Trying to change bytes at physical address $c0000 with SoftIce - if changed, after second they will be the same as original....
May be i need to intercept some native API???

Video BIOS (like any other BIOS) usually resides in ROM (Read-Only Memory). So, you can't write in it.

In DOS times there was some trick used by chpset to speed-up BIOS access (EEPROM was much slower that RAM). BIOS was copied into RAM and that RAM region was marked as Read-only and mapped in address space instead of BIOS. And for some chpsets there was known way to unlock mapped region of RAM, modify its content (e.g. replace font characters bitmap) and lock region back. But mapping of RAM instead of BIOS ROM was supported by chipset, not by CPU itself...