https://lowendmac.com/2014/the-g5-and-mac-os- … han-youd-think/

All classic Mac OS would be entirely 32-bit, G5 was the first 64-bit mac CPU and it came *waaaay* after apple was done with OS9.

I'm a bit surprised they didn't try harder considering some of the Powermac G5s could be equipped with up to 16GB RAM but I guess they would have known not to bother since the x86 switch was coming.

Expack3 wrote on 2023-06-26, 14:14:

Anyways, I recently came across a claim I hadn't heard before: namely, games and applications which run on PPC Mac OS (aka Mac OS Classic) are 32-bit only. As I'm more familiar with how Windows has historically handled EXEs of differing bits, I'd be very interested to hear how Mac OS handles it, if at all.

Sounds about right. A more interesting topic in this area would be how they handled the fact that binaries could contain 68000 code, PowerPC code, or both. There was also early Mac hardware where the top 8 address bits were ignored and then abused as flags (including by the firmware) and this had to be worked around aka "32-bit addressing."

Error 0x7CF wrote on 2023-06-26, 20:45:

I'm a bit surprised they didn't try harder considering some of the Powermac G5s could be equipped with up to 16GB RAM but I guess they would have known not to bother since the x86 switch was coming.

Maybe, I think for a while there, in general, there was a belief in sticking with 32-bit userspace: http://web.archive.org/web/20190108141947/htt … -and-elsewhere/

The thing is that the modern web is so bloated (not just the sites but the shift to users keeping 5000 tabs open), and desktop applications bloated as a result of the move to Electron, that programmers can't write anything bigger than "hello world" in a 32-bit address space any longer 😁

If you mean in comparison to earlier word sizes, early Macs were limited to a 24-bit address space (This was due to a limitation of the Motorola 68000). Once Macs began running into issues with machines that had more than 8 MiB of RAM, the 32-bit addressing mode was added. Up until System 7, you could switch between 32-bit and 24-bit addressing, because some old software did not work in 32-bit addressing. I think your ROM had to be 32-bit "Clean" to take full advantage of 32-bit.

The transition to 32-bit addressing was done in the 68k days; by the time the PowerPC was introduced, 32-bit-only addressing was the norm.

Error 0x7CF wrote on 2023-06-26, 20:45:

https://lowendmac.com/2014/the-g5-and-mac-os- … han-youd-think/

All classic Mac OS would be entirely 32-bit, G5 was the first 64-bit mac CPU and it came *waaaay* after apple was done with OS9.

I'm a bit surprised they didn't try harder considering some of the Powermac G5s could be equipped with up to 16GB RAM but I guess they would have known not to bother since the x86 switch was coming.

The G5 was comparable to the Pentium IV. Powerful, but very hot and power hungry.
Altivec support on G5 was tacked-on, merely, not improvimg things much further.

And while Mac OS X 10.5 Leopard with 64-Bit support was available, it hadn't been loved.

Mac OS X 10.4 Tiger was quicker, more responsive and had Classic Environment.
Patched versions of OS 9.2.2 could run on G5 via Classic Environment.

And Classic had been needed desperately, still.
Because many users in the, say, picture editing field had a need to run classic Mac OS 8/9 applications in conjunction with recent OS X or Carbon applications (say Photoshop):
Say older DTP software, because new applications hadn't been written for Mac platform anymore.

Except for popular software, I mean. After early 2000s, the amount of new commercial Macintosh applications and games had decreased steadily.
A far cry to the 90s, in which a lot of niche applications had been sold.

Mac OS X Snow Leopard 10.6 (intel) was going to be the next star after Tiger.
It couldn't run Clasic Environment, but at least run both Intel and PPC binaries.
It also supported Carbon application, Intel and PPC.
So some Mac OS 8/9 applications could run on Snowy if they had been compiled for Carbon API rather than native Mac OS API.

Madd the Sane wrote on 2024-11-23, 04:36:

Up until System 7, you could switch between 32-bit and 24-bit addressing, because some old software did not work in 32-bit addressing. I think your ROM had to be 32-bit "Clean" to take full advantage of 32-bit.

Yes, but funnily the application wasn't from Apple but bought from Connectix.
https://en.wikipedia.org/wiki/MODE32

The 24-bit addressing limit was a software problem, not a hardware one. The address pointer was always 32-bits wide. Early Macintosh system software and applications used the, then unused, upper 8 address bits as a flag byte to conserve memory.

As for the G5, 64-bit addressing wasn't a waste per se. You could use 4+GB of RAM in the machine (the rare few that had it at the time), but 32-bit applications were limited in what they could use on a per-process basis like 32-bit WoW applications are limited on Windows. When Apple switched to 64-bit, they also eliminated the use of many of the C-based Carbon APIs. You could basically only program 64-bit applications in Cocoa. Most software houses weren't going to rewrite their stuff for PPC since the Intel transition had already happened at that point.