On Tue, Apr 05, 2011 at 11:09:08AM -0400, Brad Parker wrote: > It might be confused, but I'd think you could get access > to the TSC register on most modern cpu's running windows.
TSC doesn't work on any motherboard with multiple processors or any hyperthreading processors or any processor with power-saving enabled or any processor that can be hibernated. Some "recent" intel processors run TSC constant rate rather than being a instruction counter. Good for this app, but now you need CPU detection code and/or it'll only work on the most recent intel. On linux google for "constant_tsc". I would imagine there is also a way to do this on legacy OS; OS/2, windows, msdos, etc. Also AMD does TSC different than intel w/ respect to syncing multiple cores / hyperthreading. So intel and AMD boards will have different behavior if they are both HT and depending on how the OS behaves w/ respect to core locking a process under load. May or may not matter. TSC can be used at great peril, but it literally either needs separate builds per CPU mfgr and CPU family, or it needs some pretty complicated steering logic, or it needs a secondary control loop outside the TSC control loop (probably using wall clock) to self tune the TSC. Then there's "seccomp mode" sort of a virtualization / secure chroot kinda thing, which no one uses, which disables TSC, but people keep on claiming they'll sandbox their browser into it RSN, etc. Probably not relevant but TSC can be messed up by some strange rarely deployed virtualization technologies, so keep that in mind for bug triage time. TSC is a "there be dragons" area on the map, although it does technically exist. _______________________________________________ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
