Why 64-bit?
- Thread starter mkillio
- Start date
The move to 64-bit (in the beginning) was more for memory reasons; with 32-bit we're all looking at a maximum 4GB of addressable memory, but with 64-bit, there is about 1.7E10 GB addressable. 
All the memory in the world right now probably doesn't even add up to that.
edit: 64-bit O/S so far do not address nearly that much, but rather something on the order of 1-256TB, but that is still a heck of a lot of memory.
All the memory in the world right now probably doesn't even add up to that. edit: 64-bit O/S so far do not address nearly that much, but rather something on the order of 1-256TB, but that is still a heck of a lot of memory.
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I'd like to pop in a quick question: Why were Jaguar and N64 consoles in their day marketed as 64-bit systems (i.e having 64-bit wide general purpose CPU registers storing 64-bit code for execution, a la x86-64 etc), and indeed Dreamcast and PS2 as 128-bit? Is/was it correct to call these architectures true 64 and 128-bit systems respectively? More recently (since and including Xbox1) it's not fashionable to refer to games consoles as 'x-bit' in marketing...
arjan de lumens
Veteran
N64 had a 'true' 64-bit processor, in that its general-purpose address/data registers were indeed 64 bits wide, although, given that it had only 4MB RAM, its 64-bit-ness was essentially useless (except for marketing), and rarely used for anything at all.
Interestingly, its successor, the GameCube, is NOT 64-bit - the address/data registers of its main CPU are only 32 bits wide.
Atari Jaguar achieved "64 bits" by adding together the bit widths of different parts of the system; there were no individual execution units that could work on 64-bit addresses or data. The CPU was a Motorola 68000, which is widely considered 16-bit.
The CPUs in Dreamcast and PS2 contained 128-bit-wide vector execution units, thus "128-bit". The general-purpose address/data registers were 32-bit in Dreamcast and 64-bit in PS2.
To this date, no processor that I have ever heard about has actually implemented a 128-bit address space; even if you take all the DRAM manufactured in the world up until today, you still aren't close to filling up even a 64-bit address space!
Interestingly, its successor, the GameCube, is NOT 64-bit - the address/data registers of its main CPU are only 32 bits wide.
Atari Jaguar achieved "64 bits" by adding together the bit widths of different parts of the system; there were no individual execution units that could work on 64-bit addresses or data. The CPU was a Motorola 68000, which is widely considered 16-bit.
The CPUs in Dreamcast and PS2 contained 128-bit-wide vector execution units, thus "128-bit". The general-purpose address/data registers were 32-bit in Dreamcast and 64-bit in PS2.
To this date, no processor that I have ever heard about has actually implemented a 128-bit address space; even if you take all the DRAM manufactured in the world up until today, you still aren't close to filling up even a 64-bit address space!
chavvdarrr
Veteran
actually, today's implementation of x86-64 on AMD uses 40-bits for addressing data, so right now, K8 can directly address up to 2^40 - 1 TB RAM. Rumours are that next generation will have 48 address lines, so being able to address up to 256 TB RAM
As you see, even 40 lines is much more than the amount of RAm anyone will use in his desktop PC in next 2-3 years
As you see, even 40 lines is much more than the amount of RAm anyone will use in his desktop PC in next 2-3 years
