From: J.P. N. <jn...@pr...> - 2006-07-19 13:47:14
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The performance advantage to using thumb is that the chip can better utilize instruction cache. I remember doing a project in college that was supposed to address the usage of streaming instruction compression to meet the same end. That approach didn't work too well. ;) =20 ________________________________ From: gum...@li... [mailto:gum...@li...] On Behalf Of Daniel Foisy Sent: Monday, July 17, 2006 16:09 To: General mailing list for gumstix users. Subject: Re: [Gumstix-users] 270 As far as I can tell, the PXA270 also supports thumb - unless you're hurting for memory and can take a hit on cycles, it's simpler to just to leave the processor in 32-bit mode (not sure how thumb works with Linux either). Normally you enter Thumb mode using the BX instruction or BLX at the assembly or simply use -mthumb and -mthumb-interwork if using GCC (and other compilers?). All exception handling is in 32-bit mode. Dan Nicholas S-A wrote:=20 With my total lack of intimate knowledge of the whole processor, the main thing I notice is that it no longer supports 'thumb' as one of=20 it's features. :( =09 *pets his 255* =09 (Out of curiousity, what is 'thumb' under features on the 255?) =09 =20 =09 It means you can connect it to the thumbstix without problems :-) Just kidding. thumb mode is a processor mode that uses 16 bit instructions instead of=20 32 bit instructions, at the cost of a much smaller instruction set,=20 which saves about 40% code space. it basically just makes all code a=20 lot smaller. I believe it is entered dynamically, so you can run certain segments of simple code that don't need complex instructions in=20 thumb mode, then switch back to normal mode again, but don't quote me=20 on that. =09 nick =09 =09 =09 ------------------------------------------------------------------------ - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash =09 http://www.techsay.com/default.php?page=3Djoin.php&p=3Dsourceforge&CID=3D= DEVDE V _______________________________________________ gumstix-users mailing list gum...@li... https://lists.sourceforge.net/lists/listinfo/gumstix-users =09 =20 |