And yes set cpu idle was specified on both, in fact the ini files are identical except for network adapter name changes. sampsa On 31 Dec 2012, at 21:41, Cory Smelosky <b4 at gewt.net> wrote: On 31 Dec 2012, at 14:40, sampsa at mac.com wrote: On 31 Dec 2012, at 20:46, Cory Smelosky <b4 at gewt.net> wrote: On 31 Dec 2012, at 08:26, sampsa at mac.com wrote: I noticed that Linux SIMH is about twice as fast on OS X. KUHAVX got about 12 VUPS when running natively on a Core i5 iMac, 24 when in a Linux VM on the same hardware. Pretty weird. Really? I've gotten 20 VUPS on both. Which version of OS X? 10.7.5 (Darwin 11.4.2 Darwin Kernel Version 11.4.2: Thu Aug 23 16:25:48 PDT 2012; root:xnu-1699.32.7~1/RELEASE_X86_64 x86_64) and 10.6.8 (10.8.0 Darwin Kernel Version 10.8.0: Tue Jun 7 16:32:41 PDT 2011; root:xnu-1504.15.3~1/RELEASE_X86_64 x86_64 Interesting. Which version of SIMH and do you remember to SET CPU IDLE? -- Cory Smelosky http://gewt.net/ Personal stuff! http://gimme-sympathy.org/ My permanently-a-work-in-progress pet project.