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The first 640K was only an issue with older MS-DOS based systems which limited memory to 1MB. The upper memory was reserved specifically for system use, leaving 640K available to the user (originally the limit was 512K). Extended and enhanced memory drivers allowed additional memory to be used above the 1MB barrier. These barriers no longer exist as memory is allocated virtually on all modern systems. To all intents and purposes, a 32-bit system has a full complement of 4GB of memory available even when it physically has less than 4GB installed. This is achieved by using disk space to swap the contents of memory in and out of RAM as required. A 64-bit system essentially has unlimited memory, only limited by the amount of available disk space. A single 64-bit system can address far more memory than physically exists in the world today.
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Using the DOS memory model the first 640K of memory is known as what?
SEMI
What is conventional memory in PC?
Conventional memory refers to the memory reserved to run DOS programs in a computer system. DOS only uses the first 640 kb of memory in a PC.
How big conventional memory?
640K to 1M - some cite either Also called "Real Memory"
Name two utilities that windows uses to manage memory above 640K?
himem.sys
What is the purpose of HIMEM.SYS?
A Device Driver Utility used by DOS and Windows 9x/Me to manage memory above 640K.
What is upper memory?
It is the uppermost region of the PC memory map for ROM, usually from 640K up to 1024K, originally reserved for BIOS, device drivers, and TSRs.
What are Port and memory addresses expressed as?
Port and memory addresses are expressed as Hexadecimal Numbers
What is a UMB?
It stands for 'Upper Memory Block. It refers to the area of memory that exists outside the 640K of Ram (that DOS base programs opperate in), that can be utilized by some programs.
If memory addresses are used by the CPU to access memory then what are io addresses used for?
To read and write to I/O
Who makes memory addresses?
Those who address on the nature of memory. :-)
How can you distinguish memory addresses from you IO port addresses?
Not possible, both are numbers.
Specific location of a byte of storage in the computer's memory?
Memory Addresses
