In my case, gcc with the default makefile. I don't use VC (or the OS it runs on) unless serious force is applied... paul On Aug 10, 2012, at 3:02 AM, <hvlems at zonnet.nl> wrote: How was simh compiled? I used Visual C and the difference between running the compiler with optimization on or off made quite a difference for the generated code. And gcc might compile even faster codefiles. Hans -----Original Message----- From: Sampsa Laine <sampsa at mac.com> Sender: owner-hecnet at Update.UU.SE Date: Thu, 09 Aug 2012 23:07:24 To: <hecnet at Update.UU.SE> Reply-To: hecnet at Update.UU.SESubject: Re: [HECnet] AXP Emulation Why is SIMH so slow though? As far as I can understand, one MIPS is roughly one VUPS, correct? So how come I get 14 VUPS on the same host running SIMH whilst my Hercules install peaks at 180? Are the architectures that different (obviously they are) or what is it? Sampsa