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Dividing the Linux desktop
LWN.net Weekly Edition for June 13, 2013
A report from pgCon 2013
Little things that matter in language design
Supporting 64-bit ARM systems
Posted Jul 11, 2012 14:12 UTC (Wed) by mwsealey (guest, #71282)
It's not like PPC where the instruction encodings are identical to a high degree and 64-bit code barely has a handful of extra instructions for dealing with 64-bit values directly. Power Architecture was designed very, very well from the beginning, and the mnemonics are identical and the generated bytecode is identical barring the 64-bit specifics. You can't say that about ARM. ARM decided to reinvent the architecture to get rid of all that cruft (but they have to keep compatibility with at least the ARMv7).
Most of the available userspaces are going to stay ARMv7-A for a long, long time.. like running a 64-bit kernel with a 32-bit userspace is common on x86 these days (and x32 just compounds it). Those that need to have 64-bit userspaces will have them..
Posted Jul 11, 2012 22:02 UTC (Wed) by ncm (subscriber, #165)
DEC provided a translator from x86 to Alpha, and the translated code ran lots faster on Alpha than the original code did on x86. IIRC, interpreted x86 ran as fast as x86. It didn't save them in the end. How the market will respond to a new architecture depends on details, and nobody knows which details will turn out to be important.
Compatibility can be a trap: IBM OS/2 ran windos programs unchanged. windos could not run OS/2 programs. Which target should you code for?
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