Path: utzoo!utgpu!watserv1!watmath!att!att!linac!uwm.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!virtech!cpcahil From: cpcahil@virtech.uucp (Conor P. Cahill) Newsgroups: comp.unix.sysv386 Subject: Re: UNIX Performance Penalties Keywords: UNIX vs DOS Message-ID: <1990Nov01.133155.8451@virtech.uucp> Date: 1 Nov 90 13:31:55 GMT References: <652@anacapa.NCEL.Navy.Mil> <2202@sixhub.UUCP> Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill) Organization: Virtual Technologies Inc., Sterling VA Lines: 23 In article peter@ficc.ferranti.com (Peter da Silva) writes: >In article <2202@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes: >> If your application is compiled for 32 bit unix using a good >> compiler, and uses 32 bit int data, you will get about 2:1 (I didn't >> believe it until I measured it either). > >I'm surprised it's so small. The speed difference for pure-CPU on >a 286 between small and large model (accessing 20000-int-long array >at effectively random versus accessing a 40000-int-long array) is on >the order of 11:1! Thats because you guys are talking about apples and oranges. The performance difference between small and large models deals with the additional overhead of computing addresses using the segment descriptor (including maintaining the segment descriptors for every far address). The benefits of using a 32 bit compiler on a 32 bit machine deals with using a natural format integer (as far as the processor is concerned) vs having to fake it. -- Conor P. Cahill (703)430-9247 Virtual Technologies, Inc., uunet!virtech!cpcahil 46030 Manekin Plaza, Suite 160 Sterling, VA 22170