Date: Mon, 4 Jan 1999 12:05:48 -0500 (EST) From: Alfred Perlstein <bright@hotjobs.com> To: sparc@FreeBSD.ORG Subject: arch questions Message-ID: <Pine.BSF.4.05.9901041155450.37756-100000@bright.fx.genx.net>
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I was under the impression that the goal of a sparc64 port was a 64 kernel AND a 64 bit userland. It seems that all the ports i've seen have a 64bit kernel and a 32 bit userland. (solaris 7, linux, netbsd (when it's released)) I'm unsure i see the benifit of doing this because: a) the insturctions stay at 32bits wide, so we don't have much bloat to worry about, and we don't incur much penalty for using larger ints. (if we choose to use 64 bit ints) b) using 64bit values/ABI is MUCH cheaper, in fact using old sparc32 methods of accessing memory can seriously hurt performace as several opcodes to access 64bit values in sparc32 code are depreciated and can cause massive pipeline stalling and traps to the OS to emulate certain VERY depreciated opcodes c) the sparc64 FPU is considerably more advanced than the sparc32 FPU, the Y register is depreciated and can cause major performance loss. In fact when i saw how you accomplish an undertermined product of 'x' and 'y' it sort of turned my stomach (jump, setup, 32 mulcc's, ret) The only benifit I see (which doens't apply to us that much) is: If your userland is 32bit, then it's much easier not to have to port that huge section of code. The only reason it might help us is that since intel is 32bit, it may ease the porting by a very small margin, but this doesn't seem to be worth the performance losses i mentioned above, especially in our case when we don't have ANY sparc bits at this point in time. am i missing something? I would like to aim for a 64bit userland to max out the performance of the work. questions? comment? corrections? thanks, Alfred Perlstein - Programmer, HotJobs Inc. - www.hotjobs.com -- There are operating systems, and then there's FreeBSD. -- http://www.freebsd.org/ 3.0-current To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-sparc" in the body of the message
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