Date: Thu, 16 Oct 2008 20:25:35 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Taku YAMAMOTO <taku@tackymt.homeip.net> Cc: freebsd-mobile@freebsd.org, stas@freebsd.org, freebsd-arm@freebsd.org, freebsd-current@freebsd.org, zbeeble@gmail.com, "M. Warner Losh" <imp@bsdimp.com> Subject: Re: RFC: PCI SD host controller driver & mmc/mmcsd modules improvements Message-ID: <48F7790F.5000904@FreeBSD.org> In-Reply-To: <20081017013946.3534221e.taku@tackymt.homeip.net> References: <48F7121A.2010307@FreeBSD.org> <20081016.081628.43009259.imp@bsdimp.com> <48F75773.7030100@FreeBSD.org> <20081016.092844.-1548243521.imp@bsdimp.com> <20081017013946.3534221e.taku@tackymt.homeip.net>
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Taku YAMAMOTO wrote: > On Thu, 16 Oct 2008 09:28:44 -0600 (MDT) > "M. Warner Losh" <imp@bsdimp.com> wrote: > >> In message: <48F75773.7030100@FreeBSD.org> >> Alexander Motin <mav@FreeBSD.org> writes: >> : No, it's opposite. With lower frequency I have proportionally smaller >> : delays (more loop iterations). I don't remember exact numbers now, but >> : general tendency was like: with 2400MHz - 10 iterations, with 1200MHz - >> : 20 iterations and with 100MHz - 240 iterations. But neither syslog, nor >> : my eyes saw any visible delay there. >> >> You have more iterations. I'd have expected less. This doesn't say >> anything at all about DELAY, per se. If you are waiting for 1M cycles >> at 100MHz, it is only .01s, while at 10MHz it is .1s. Delay is >> implemented by reading a counter in the 8254 that's been calibrated. >> So unless the clock that's clocking it is running FASTER, delay won't >> be the source of additional iterations. >> >> Hmmm, looking at the i386 delay code, it looks like it depends on >> tsc_frequency being right when tsc isn't broken. If that's set >> bogusly, that could cause DELAY to be slower... > > I have a Core 2 Duo whose TSC ticks regardless of how EST is set. > In conjunction of tsc_freq_changed() function defined in tsc.c, > tsc_freq becomes lower than actual, thus shorter DELAY(). > > Maybe his machine has the same. Indeed: CPU: Intel(R) Core(TM)2 Duo CPU T7700 @ 2.40GHz (2394.01-MHz K8-class CPU) Origin = "GenuineIntel" Id = 0x6fb Stepping = 11 Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP, MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS, HTT,TM,PBE> Features2=0xe3bd<SSE3,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16, xTPR,PDCM> AMD Features=0x20100800<SYSCALL,NX,LM> AMD Features2=0x1<LAHF> Cores per package: 2 FreeBSD 8.0-CURRENT amd64. -- Alexander Motin
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