Why does my system see all my memory above 16MB on POST but DOS only sees 16MB.?

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  • Wednesday, May 11, 2011
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  • siva
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  • When installing more than 16MB of memory, BIOS relocation must be disabled. BIOS relocation copies the video BIOS (C0000-C7FFF) and the system ROM BIOS (F0000-FFFFF) into RAM. The motherboard (BIOS?) adds 15MB to these addresses (F00000) to be able to differentiate between the ROM and RAM. Enabling the relocation feature causes the memory above 16MB to become non-contiguous and therefore inaccessible. For DOS to size and utilize the memory above 16MB you MUST disable all BIOS and video ram relocation and/or caching settings in your CMOS setup. It may slow the system down somewhat but this is a throwback to the 286 memory limitation (24 bits) for 16MB of addressable memory.

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