我有一个非常简单的(n00b)问题。
一个20位的外部地址总线给了一个1 MB的物理地址空间(2 ^ 20 = 1,048,576)。(Wikipedia)
为什么是1 MB?
2^20 = 1,048,576 bit = 1Mbit = 128KByte not 1MB我误解了一些东西。
I have a very simple (n00b) question.
A 20-bit external address bus gave a 1 MB physical address space (2^20 = 1,048,576).(Wikipedia)
Why 1 MByte?
2^20 = 1,048,576 bit = 1Mbit = 128KByte not 1MBI misunderstood something.
最满意答案
当你有20位时,你最多可以处理2^20 。 这是您的范围 ,而不是位数。
也就是说,如果你有8位,你的范围是255(无符号)而不是2 ^ 8位。
因此,使用20位可以处理2 ^ 20字节,即1MB
即20位,您可以表示从0到2^20 = 1,048,576的地址。 也就是说,您可以引用最多1MB的内存。
When you have 20 bits you can address up to 2^20. This is your range, not the number of bits.
I.e. if you have 8 bits your range is up to 255 (unsigned) not 2^8 bits.
So with 20 bits you can address up to 2^20 bytes i.e. 1MB
I.e. with 20 bits you can represent addresses from 0 up to 2^20 = 1,048,576. I.e. you can reference up to 1MB of memory.
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