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Memory Usage

Memory Chart Flags

This is a list of the possible flags in the memory chart below. These flags specify some information which will be respected by the system, when administrating the memory. The flags are:

PA - The memory page(s) are allowed to be paged out memory.
UN - The memory in the segment will be unused by the system, for the sake of compatibility.
FO - Memory cycle will be forwarded to the PCI bus.
OF - Memory cycle can be configured by the system to be forwarded to the PCI bus.
DF - The memory segment/offset/size has been fixed when designing the system.
HF - The memory segment/offset/size is fixed by hardware design.
OH - The memory segment/offset/size optional fixed by hardware in conjunction with system.
DY - Dynamicly segment/offset/size in the available memory range.


Memory Chart

This is a list of all the memory ranges in the system:

Fixed Memory
Offset Size Flags Usage
00000000h400hUNReal-Mode Interrupt Vector Table
00000400h200hUNBIOS Data Area
00000600h200hUN... (Free)
00000800h66hUN80286 Loadall workspace
00000866h79AhUN... (Free)
00001000hF000hUN... (Free)
00010000h10000hDF64 Kb Real-Mode Compatibility Segment
00020000h60000h... (Free)
00080000h10000hOF, OH... (Possible Memory hole of 128 Kb)
00090000h10000hHFBIOS Extension
Below 1 Mb10000hDY, OHDMA Channel 0 buffer (8 bit) (Required < 1 Mb)
Below 1 Mb10000hDY, OHDMA Channel 1 buffer (8 bit) (Required < 1 Mb)
Below 1 Mb10000hDY, OHDMA Channel 2 buffer (8 bit) (Required < 1 Mb)
Below 1 Mb10000hDY, OHDMA Channel 3 buffer (8 bit) (Required < 1 Mb)
000A0000h10000hHFEGA+ Graphics Buffer
000B0000h8000hHFVideo buffer on some systems
000B8000h8000hHFEGA/VGA+ Text Buffer
000C0000h20000hHF(Real-Mode) ISA Add-on BIOS. Devided into 8 x 16 Kb Segments
000E0000h10000hHF(Real-Mode) BIOS Extension. Devided into 4 x 16 Kb Segments
000F0000h10000hHF(Real-Mode) BIOS
00100000h?PA... (Free)
00E00000h200000hOF, OH... (Possible memory hole of 1 or 2 Mb)
00F80000h80000hUNFlash BIOS Area (aliased from FFF80000h)
Below 16 Mb20000hDY, OHDMA Channel 4 buffer (16 bit) Cascaded (Required < 16 Mb)
Below 16 Mb20000hDY, OHDMA Channel 5 buffer (16 bit) (Required < 16 Mb)
Below 16 Mb20000hDY, OHDMA Channel 6 buffer (16 bit) (Required < 16 Mb)
Below 16 Mb20000hDY, OHDMA Channel 7 buffer (16 bit) (Required < 16 Mb)
01000000h< 64 MbPA... (Free - Cacheable)
04000000h< 256 MbPA... (Free - Non-cacheable in L2, Cacheable in L1)
10000000hA0000hHFTop of DRAM. Forwarded to PCI (Non-cacheable)
100A0000h60000hOHOptional HiSMRAMM area
10100000h< ~4 GBHFForwarded to PCI (Non-cacheable)
FFFE0000h20000hHFProtected-Mode BIOS