On 9 juil. 2012, at 20:40, Greg Parker <gpar...@apple.com> wrote: > On Jul 9, 2012, at 5:44 AM, Vincent Habchi <vi...@macports.org> wrote: >> Modern CPU do not enforce strict alignment for integer access. You can >> perfectly access a Dword (64 bits) at any address, even or odd. It is just >> more efficient to align 64-bits words at 8-bytes boundary, 32-bits at >> 4-bytes, etc. This contrasts with the old times: for example, on a 68000 >> processor, trying to access a 16-bit word at an odd address (e.g. move.w d0, >> (a0)+ with a0 odd) would result in a exception n°3 (address error). > > Some CPUs still enforce aligned integer access, such as the ARM CPUs in some > iOS devices.
Oh, thanks for mentioning this. I was obviously thinking about Intel CPUs. I know very little about ARM. By the way, you can also access misaligned instructions on x86 processors I think, something that was not possible on 68000. If I remember correctly, the integer alignment enforcement was lifted on the 68030, which leaded to interesting hardware developments… Vincent _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
