short answer to technical question?

Nix, Robert P. Nix.Robert at mayo.edu
Wed Nov 16 20:26:12 UTC 2005


Actually, in this case 32 bit and 64 bit refer not to the natural word size, but to the address size. i.e. a 32 bit machine uses a 32 bit address for memory, and cannot address as much memory as a 64 bit machine, using 64 bit addresses, can.

In the case of the IBM mainframe computers, the natural word used to be 32 bits, but they were 31 bit machines, as the top bit of the word was reserved for something other than an address bit. The new mainframes are 64 bit machines, using all 64 bits of an address to address memory. They're still 32 bit words though; they just happen now to use two of them for an address. 

(Actually, the smallest thing the mainframe would deal with for a long time (early 1980's forward) has been 64 bits, or a double-word. The main change has been the use of larger addresses.) 


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-----Original Message-----
From: fedora-list-bounces at redhat.com [mailto:fedora-list-bounces at redhat.com] On Behalf Of Mike McCarty
Sent: Wednesday, November 16, 2005 12:21 PM
To: For users of Fedora Core releases
Subject: Re: short answer to technical question?

Gerhard Magnus wrote:
> Hello All,
> 
> 	I don't know if there's a short answer to this... but what do "32 bit"
> and "64 bit" refer to and how can I tell which applies to my computer?
> 
> Jerry

Modern PC style computers all are binary. (Most calculators are
decimal.) The word "bit" is a contraction of "binary digit".
All computers have a natural word size, measured in digits.
This is the size of word which the computer can use without
special software. If the natural size of a computer word is
8 bits, then it is called an 8 bit computer. Examples are the
8080, Z80, 68HC11, and so on. Computers whose natural word
size is 16 bits are the 8086, Z8000, 68000, etc. The 80386
and later 80x86 machines up through the Pentium class machines
were all 32 bit machines. Now, some machines have a natural
word size of 64 bits.

The only way to tell is to know what the processor chip is.

Mike
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