64-bit addressing involves computers that can locate memory addresses that are 64-bits (4 bytes) wide, allowing for a theoretical maximum of 16 exabytes (16.7 million gigabytes) of memory, though logic board and CPU configurations may add other limitations.[1][2]
History[]
The Power Macintosh G5 was first released in June 2003 with the ability to address more than 4GB of RAM with 64-bit addressing, though implementation was limited at the time. Mac OS X 10.2 (Jaguar) allowed up to 8GB of RAM on dual-core G5 models.[3] In 2005, the quad-core G5 running Mac OS X 10.4.x (Tiger) could address up to 16GB of RAM.[4]
The first Macs with Intel Core processors were introduced in January 2006 with support for 32-bit addressing only, though hardware on consumer models could only be upgraded up to 2 GB anyway. Models with Intel Core 2 processors began appearing in October 2006 with full 64-bit support. Mac OS X versions up through 10.5.8 (Leopard) still relied on a 32-bit kernel upon startup. The first time a 64-bit application was launched on a 64-bit processor, a 64-bit framework would be loaded into memory, incurring a performance and memory hit. In Mac OS X 10.6 and later, a 64-bit kernel was introduced, favoring better performance on 64-bit applications and incurring a performance and memory penalty from loading a 32-bit framework when a 32-bit application was launched. Mac OS X 10.8 (Mountain Lion) dropped support for legacy 32-bit kernel extensions.[5] macOS 10.15 (Catalina) eliminated the 32-bit framework and any remaining backward compatibility with 32-bit applications entirely.
References[]
- ↑ 32-Bit vs. 64-Bit and Why It Matters by Kayla Myrhow, Parallels. 2019-05-28.
- ↑ Memory limits in 16, 32 and 64 bit systems by Super User, StackExchange. 2013-02-22.
- ↑ The G5 and Mac OS X: Less 64-bit Than You’d Think by Daniel Knight, Low End Mac. 2014-08-15.
- ↑ Apple Power Macintosh G5 "Quad Core" (2.5) specs, EveryMac. Accessed 2022-05-22.
- ↑ Should You Recompile Your Software as a 64-Bit Executable?, Apple Developer. 2012-12-13.
External links[]
- Introduction to 64-Bit Transition Guide at Apple Developer (2012-12-13)
- Introduction to 64-Bit Guide for Carbon Developers (2013-04-23)
- Introduction to 64-Bit Transition Guide For Cocoa (2013-09-17)
- 64-bit computing at Wikipedia
