🚀 go-pugleaf

	-- Qoutation --
In article <3810013@nucsrl.UUCP> ram@nucsrl.UUCP (Raman Renu) writes:
>     As the 32-bit CPU is everywhere, is the mini-class of machines 
>moving towards 64 bit?.  In a decade we have seen the migration from 
>4->8->16->32.  Would there be a 64-bit micro-processor soon?
>
>     Any predictions?  Do we really need 64 bit processing power?

	-- Discussion --
Why do computers have a certain "word length"?

1) To contain a machine code instruction.
There is no need for even 2^16 instructions in any computer.

2) To contain a binary address to its memory.
Since silicon RAMs tend to double in density (one more address bit per
chip) every 18 months, it would take 48 years to go from 32 to 64
address bits. Heavier use of virtual memory could make this go faster.

3) To contain "atomic" data like numbers.
64 bits is good for floats and will be (is?) used by the number-
crunching society. They probably have no need for 128 bits.

4) To contain some other relevant but "atomic" information.
Consider the 36 bit wide pdp-10. 36 bits is 6 bits (six-bit code)
times 6 characters (a file name or a Fortran identifier).
This motivates 64 or even 128 bit words, since 128 bits is 16
characters times 8 bits (extended ascii).

	-- Prediction --
Most certainly, we will see 64 bit and even 128 bit computers in say 10
and 15 years respectively, but I doubt it that 256 bit computers will
ever be commercially available. Instead, new and more parallel
architectures will be invented.

	-- New question --
I'd like to modify the original question:

Is there already, or will there ever (or soon) be a computer with
truely variable word length? I.e. not machines reading "enough many
bytes", but some kind of smart memory that is given orders like:

* On address ADDR, write word DATA, that is LEN bytes long.
* Read DATA at address ADDR+1 and tell LEN how long that data is.
-- 
Name:	Lars Aronsson
Snail:	Rydsvagen 256 A:10, S-582 48 Linkoping, Sweden
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