Technology

I would say that you make a decent argument that the ALU has the strongest claim to the “bitness” of a CPU. In that way, we are already beyond 64 bit.

For me though, what really defines a CPU is the software that runs natively. The Zen4 runs software written for the AMD64 family of processors. That is, it runs 64 bit software. This software will not run on the “32 bit” x86 processors that came before it ( like the K5, K6, and original Athlon ). If AMD released the AMD128 instruction set, it would not run on the Zen4 even though it may technically be enough hardware to do so.

The Motorola 68000 only had a 16 but ALU but was able to run the same 32 bit software that ran in later Motorola processors that were truly 32 bit. Software written for the 68000 was essentially still native on processors sold as late as 2014 ( 35 years after the 68000 was released ). This was not some kid of compatibility mode, these processors were still using the same 32 bit ISA.

The Linux kernel that runs on the Zen4 will also run on 64 bit machines made 20 years ago as they also support the amd64 / x86-64 ISA.

Where the article is correct is that there does not seem to be much push to move on from 64 bit software. The Zen4 supports instructions to perform higher-bit operations but they are optional. Most applications do not rely on them, including the operating system. For the most part, the Zen4 runs the same software as the Opteron ( released in 2003 ). The same pre-compiled Linux distro will run on both.

I gave up trying to figure out what the "bitness" of CPUs were around the time the Atari Jaguar came out and people described it as 64 bit because it had 32 bit graphics chip plus a 32 bit sound chip.

It's been mostly marketing bollocks since forever.

At less than a tenth the size, this is actually a better explanation than the article. Already correcting the fact that we do at the very beginning.
If you absolutely had to put a bit width on the Zen 4, the 2x128 bit data bus is probably the best single measure totaling 256 bit IMO.

It's a link to an article I found interesting. It basically details why we're still using 64-bit CPUs, just as you mentioned.

We don't even have true 64-bit addressing yet. x86-64 uses only 48 bits of a 64 bit address and 64-bit ARM can use anything between 40 and 52 depending on the specific configuration.

Yeah, 64 bit handles almost all use cases we have. Sometimes we want double the precision (a double) or length (a long), but we can do that without being 128-bit. It's harder to do half. Sure, it'd be slightly faster for some things, but it's not significant.

Is this a question?

For the people who don't know the answer? Yes.

Not everything you see is intended for your consumption. Let people enjoy learning things.

Lobbying by the auto corporations obviously. More wheels is more better

Funny how we are moving back to bicycles, as cars aren’t scalable solution.

Some of us drive 18-wheeled vehicles.

See here's where this analogy is perfect. Sometimes a bicycle is the best solution, just like how sometimes a microcontroller is the best solution. You use the tool you need for the job, and American product design is creating way too many "smart" products just like how American town planning demands too many cars. Bring back the microcontroller! Bring back the bike!

You still had a 4GB memory limit for processes, as well as a total memory limit of 64GB. Especially the first one was a problem for Java apps before AMD introduced 64bit extensions and a reason to use Sun servers for that.

Interesting! Do you have a link to a write up about this? I don’t know anything about the windows memory manager

I'm not sure what you are talking about. Linux got PAE in 1999. Windows XP got PAE in 2001.

Not really, Raspberry Pi had that same issue with its 32 bit distros.

I think it’s a D-tier article. I wouldn’t be surprised if it was half gpt. It could have been summarized in a single paragraph, but was clearly being drawn out to make screen real-estate for the ads.