dcr0801%ritcv@cs.rit.edu (12/17/89)
I'd like to thank everyone who responsed to my question about accessing memory over 1 Meg. in protected mode on an IBM. Here is the answer: System Control Port A (0x92) can be used to enable or disable the Alternate Gate Address 20 signal. When Bit 1 of this port is set to 0, address lines 20-23 are forced to 0. This way, any address generated over 20 bits (access over 1MB) will be wrapped around to the lower Meg. Enabling this signal (setting Bit 1 on) will allow the full address (24 bits in 80286) to be placed into the address bus. (IBM Tech. Ref. , Compatability Section, page 3-26,3-23,3-38,3-50 for the PS/2 Models 50,60,70, and 80 respectivily.) Thanks again for everyone that replied. I hope this information will help someone else out of a bind in the future. Dave Rein (dcr0801@ultb.isc.rit.edu) "I just goes to show what you can do if you're a total psychotic" - Woody Allen