896k.txt Access

High-end EGA and VGA cards utilized the A segment for their frame buffers, making the 704K/896K mod incompatible with modern (for the time) graphics.

The 896K.txt methodology relies on the fact that while the memory segments A000hcap A 000 h FFFFhcap F cap F cap F cap F h 896K.txt

The original IBM PC architecture utilized the Intel 8088 processor, which had a 20-bit address bus capable of addressing 1 MB ( 2202 to the 20th power High-end EGA and VGA cards utilized the A

). On systems using standard MDA or CGA video cards, this segment was often empty. By installing RAM chips that responded to these addresses, users could gain an additional 64K, bringing the total contiguous memory to . Standard MS-DOS/PC-DOS versions could recognize this memory without a specialized BIOS. 2.2 Reaching 896K By installing RAM chips that responded to these

If a user lacked a high-resolution video card or specific expansion ROMs, segments B and E could sometimes be populated with RAM.

Because the IBM BIOS did not officially support RAM in these segments, some software that bypassed DOS to check memory limits would fail to "see" the extra space. 4. Historical Significance

Achieving 896K required more aggressive "filling" of the upper memory area (UMA). This involved: