Content deleted Content added
Line 80:
Another consideration is the data model used for [[Device_driver|drivers]]. Drivers make up the majority of the operating system code in most modern operating systems (although many may not be loaded when the operating system is running). Many drivers use pointers heavily to manipulate data, and in some cases have to load pointers of a certain size into the hardware they support for [[Direct_memory_access|DMA]]. As an example, a driver for a 32-bit PCI device asking the device to DMA data into upper areas of a 64-bit machine's memory could not satisfy requests from the operating system to load data from the device to memory above the 4 gigabyte barrier, because the pointers for those addresses would not fit into the DMA registers of the device. This problem is solved by having the OS take the memory restrictions of the device into account when generating requests to drivers for DMA.
==Current 64-bit processor architectures==
64-bit [[processor architecture]]s (as of 2005) include:
* The [[DEC Alpha]] architecture (view [http://research.microsoft.com/~gbell/Digital/timeline/64-bit.htm ALPHA 64-bit timeline])
Line 94:
* MIPS Technologies' MIPS IV, MIPS V, and MIPS64 [[MIPS architecture|architectures]]
* HP's [[PA-RISC family]]
Some 64-bit processor architectures can execute 32-bit code natively without any performance penalty, such as AMD64, MIPS64,Sparc64, zSeries and PowerPC64, etc. This kind of support is commonly called ''biarch support'' or more generally ''multi-arch support''.
==Beyond 64 bits==
| |||