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This allowed a 16-bit address register, which would normally be able to access 64 KB of memory space, to access 1 MB of memory space. This segmenting of the memory space into discrete blocks with specific tasks carried over into the programming languages of the day and the concept is still widely in use within modern programming languages.
Another example in the same computer family was the 16-bit protected mode of the 80286 processor, which, though supporting only 16 MB of physical memory, could access up to 1 GB of virtual memory, but the combination of 16-bit address and segment registers made accessing more than 64 KB in one data structure cumbersome.
In a system using segmentation, computer memory addresses consist of a segment id and an offset within the segment. [3] A hardware memory management unit (MMU) is responsible for translating the segment and offset into a physical address, and for performing checks to make sure the translation can be done and that the reference to that segment and offset is permitted.
Direct address: ADD.A address 1 — add the value stored at address 1; Memory indirect: ADD.M address 1 — read the value in address 1, use that value as another address and add that value; Many ISAs also have registers that can be used for addressing as well as math tasks. This can be used in a one-address format if a single address register ...
A memory address a is said to be n-byte aligned when a is a multiple of n (where n is a power of 2). In this context, a byte is the smallest unit of memory access, i.e. each memory address specifies a different byte. An n-byte aligned address would have a minimum of log 2 (n) least-significant zeros when expressed in binary.
The range of addressing of memory depends on the bit size of the bus used for addresses – the more bits used, the more addresses are available to the computer. For example, an 8-bit-byte-addressable machine with a 20-bit address bus (e.g. Intel 8086 ) can address 2 20 (1,048,576) memory locations, or one MiB of memory, while a 32-bit bus (e.g ...
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For example, in an interleaved system with two memory banks (assuming word-addressable memory), if logical address 32 belongs to bank 0, then logical address 33 would belong to bank 1, logical address 34 would belong to bank 0, and so on. An interleaved memory is said to be n-way interleaved when there are n banks and memory location i resides ...