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Here is the problem I am working on

The Problem: A high speed workstation has 64 bit words and 64 bit addresses with address resolution at the byte level. How many words can in be in the address space of the workstation?

I defined the different terms in the problem

  • Word Size - Processor natural unit of data. The word size determines the amount of information that can be processed in one go
  • Byte Level Addressing - Hardware architectures that support accessing individual bytes within a word
  • 64 Bit Addressing - You have have 64 bits to specify an address in Runtime memory that holds an instruction or data
  • Address Space - Running program's view of memory in the system

How would you go about using all these definitions to solve this problem?

From 64 bits, I know that technically there are 2^64 locations in memory and from 64 bit words, that a processor processes 8 bytes a time. But I don't know how to use that information to conclude how many words are in the address space of the computer.

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committedandroider
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  • If a CPU has 64-bit registers and you are using 64-bit words, then you can address a single word, in a single register. – Ramhound May 31 '15 at 01:45
  • Each word takes up 8 memory locations? – committedandroider May 31 '15 at 19:00
  • No; read what I said; I didn't say that – Ramhound May 31 '15 at 19:29
  • does a 64 bit word mean that the word(amount of data processed by CPU at one time) takes up 64 bits or does it mean that it takes 64 bits to address the word? – committedandroider May 31 '15 at 20:47
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    A 64-bit processor has 64-bit registers ( look up what a register is if you don't understand ). All data fit into registers. You indicated in your example that a word was 64-bits, which means a single word, would fit into a single register. David's answer indicates how many 8-bit words can fit, and his answer is correct, for 8-bit words though. He used bytes, though, for some reason. – Ramhound May 31 '15 at 21:09
  • Thanks!! Can you look over my answer to my other question on caching? http://stackoverflow.com/questions/30555623/how-many-bits-are-in-the-address-field-for-a-directly-mapped-cache – committedandroider May 31 '15 at 21:15

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Since we have 64-bit addresses and address resolution is at the byte level, 2^64 bytes can be addressed. Since each word is 8 bytes, (2^64)/8 words can be addressed.

David Schwartz
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