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At some point Apple is going to discontinue 32bit iOS - just like they did with OSX, they need about 3 years before they can do this. It makes sense to start ea
by rythie 13y ago
At some point Apple is going to discontinue 32bit iOS - just like they did with OSX, they need about 3 years before they can do this. It makes sense to start early, because at some point they'll only be making devices with 4GB+ of memory (samsung already make 3GB phone).
- tadfisher 13y agoYou don't need a 64-bit architecture to address more than 4GB of memory. The real benefit is the architecture update.
- mikeash 13y agoYou don't strictly need it, but you need it if you want a single app to be able to use more than 4GB of memory sanely.
- reaperhulk 13y agoUnless your ARM has LPAE you do. I'm unsure if any ARMv7 chips out there are using LPAE yet? Anybody know? (Memory addressing info from ARM re: LPAE and ARMv8: http://infocenter.arm.com/help/topic/com.arm.doc.den0001c/DEN0001C_principles_of_arm_memory_maps.pdf http://infocenter.arm.com/help/topic/com.arm.doc.den0001c/DE...)
- masklinn 13y agoThe Cortex A7 and A15 support LPAE.
- mbell 13y agoIf you're addressing more than 4GB of physical memory (actually, ~3 to 3.5GB ish), you're using PAE, 32 vs 64 bit doesn't have any relevance to this. ARMv8 still uses a modified version of LPAE and x86_64 also uses an extension of PAE when running in 64bit mode. I don't know of a 64 bit architecture that doesn't use a PAE style table mapping system, i.e. none are directly addressing physical memory (I'm sure there is an arch out there somewhere that does, just not one I know of one in common use).
- masklinn 13y agoAt the process level you do, for both physical and virtual. And because of MMIO you don't even get 4GB virtual in 32b.