Windows 7 - Win7: Enabling HPET, bcdedit /set useplatformclock true (command)

http://www.sevenforums.com/general-discussion/184992-win7-enabling-hpet-bcdedit-set-useplatformclock-true-command.html

Win7: Enabling HPET

1.Hello,

I would like some help to understand a few things about Windows 7+ HPET and Bios+ HPET. To start it was my understanding that if you enabled HTEP in the bios Windows 7 would automatically be using HTEP. However, I'm reading that it does not and will still use the Time Stamp Counter (TSC). So I'm not sure what point it would be enabling it from the bios.

2ndly, using the command bcdedit /set useplatformclock true (then reboot) is said to enable HPET using Win 7. While bcdedit /deletevalue useplatformclock (then reboot) is said to remove it. To test to see if it's working or not you have to use either:A. Timer Function Performance (run the program before and after the tweak to see if the QueryPerformanceFrequency() freq value increased or not)B. WinTimerTester_1.1 (from UncleWebb to see if you have a 1.0000 ratio at or near 100 seconds) To see if it improves anything or not. From Unclewebbs post he addresses the use of SetFSB. From another point of view it helps improve slow connections when using this application from here.

Should we be using Windows 7's HPET or stick to TSC for everyday use and gaming?

2.Welcome back to Seven forums. I suspect your mean HPET, not HTEP?If so here is a Wiki on it. High Precision Event Timer - Wikipedia, the free encyclopedia

3. HPET ModeCommon Options : 64-Bit Mode, 32-Bit ModeQuick ReviewThis BIOS option is linked to the HPET Support BIOS option. HPET Support must be enabled for this BIOS option to be active.The HPET, short for High Precision Event Timer, is a new system timer developed by Intel and Microsoft to replace the four system timers currently in use. Some HPETs have 64-bits wide registers which can also run in the 32-bit mode. This is where the HPET Mode BIOS option comes in.Setting it to the 64-Bit Mode allows the 64-bit operating systems and applications to make full use of the HPET's 64-bit registers.Setting it to the 32-Bit Mode forces the HPET's 64-bit registers to run in the 32-bit mode. This allows proper operation when used with a 32-bit operating system.If you are using a 64-bit operating system, you should select the 64-Bit Mode so that the operating system and 64-bit applications can make full use of the HPET's 64-bit registers. There is no harm in selecting the 32-Bit Mode although it will mean a potential reduction in counter resolution and/or functionality.If you are using a 32-bit operating system, you should select the 32-Bit Mode.If you are dual-booting between a 64-bit operating system and a 32-bit operating system and both support the HPET, select the 32-Bit Mode. If the 64-bit operating system supports HPET while the 32-bit operating system does not (e.g. Windows XP), then you can select the 64-Bit Mode.

If you like to know more about this and other BIOS settings, why not subscribe to the full BIOS Optimization Guide? Click here to find out how you can do that now!

Links: Discuss BIOS options here in our forums | Back to the list of BIOS options4. By default Windows 7 uses different timers in the CPU to calculate stuff. HPET is the newest and best of these timers, but because of default combination of timers it takes longer time for CPU to keep up all the timers and sync between them. Forcing Windows to use HPET only improves performance and leads to greater FPS.

Steps to enable this tweak:

4.1. Enable HPET in BIOS. If you have HPET option in BIOS then your hardware can support HPET.

4.2. Enable HPET in Windows by giving this command in admin credential CMD:bcdedit /set useplatformclock true

4.3. Reboot

High Precision Event TimerFrom Wikipedia, the free encyclopediaJump to: navigation, search The High Precision Event Timer is a hardware timer used in personal computers. It was developed jointly by Intel and Microsoft and has been incorporated in PC chipsets since circa 2005. Formerly referred to by Intel as a Multimedia Timer,[1] the term HPET was selected to avoid confusion with the multimedia timers software feature introduced in the MultiMedia Extensions to Windows 3.0.[2]Older operating systems that do not support a hardware HPET device can only use older timing facilities, such as the programmable interval timer (PIT) or the real-time clock (RTC). Windows XP, when fitted with the latest HAL (hardware abstraction layer), can also use the processor's Time Stamp Counter (TSC) or Power Management Timer (PMTIMER), together with the RTC to provide operating system features that would, in later Windows versions, be provided by the HPET hardware. Confusingly, such XP systems quote "HPET" connectivity in the device driver manager even though the Intel HPET device is not being used.FeaturesAn HPET chip consists of a 64-bit up-counter (main counter) counting at a frequency of at least 10MHz, and a set of (at least 3, up to 256) comparators. These comparators are 32- or 64-bit wide. The HPET is programmed via a memory mapped I/O window that is discoverable via ACPI. The HPET circuit in modern PCs is integrated into the southbridge chip.[note 1]Each comparator can generate an interrupt when the least significant bits are equal to the corresponding bits of the 64-bit main counter value. The comparators can be put into one-shot mode or periodic mode, with at least one comparator supporting periodic mode and all of them supporting one-shot mode. In one-shot mode the comparator fires an interrupt once when the main counter reaches the value stored in the comparator's register, while in the periodic mode the interrupts are generated at specified intervals.Comparators can be driven by the operating system, e.g. to provide one timer per CPU for scheduling, or by applications.ApplicationsThe HPET can produce periodic interrupts at a much higher resolution than the RTC and is often used to synchronize multimedia streams, providing smooth playback and reducing the need to use other timestamp calculations such as an X86-based CPU's RDTSC instruction.Comparison to predecessorsHPET is meant to supplement and replace the 8254 programmable interval timer and the RTC's periodic interrupt function. Compared to these older timer circuits, the HPET has higher frequency (at least 10MHz) and wider 64-bit counters (although they can be driven in 32-bit mode).[1]While 8254 and RTC can, similarly to HPET, be put in one-shot mode, the set-up process is so slow that their one-shot mode is not used in practice for tasks requiring precise scheduling.[3] Instead, 8254 and RTC are typically used in periodic mode with very small time interval. For example, if an application needs to perform several short (some milliseconds, perhaps) waits, it is better to have a periodic timer running constantly with 1ms period because of the high setup cost of an 8254 or RTC one-shot timer. This causes an interrupt on every millisecond even if the application needs to do actual work less frequently. With HPET, the extra interrupts can be avoided, because the set-up cost of a HPET one-shot timer is considerably smaller.CompatibilityOperating systems designed before HPET existed cannot use HPET, so work only on hardware that has other timer facilities. Newer operating systems tend to be able to use either. Some hardware has both. Indeed most current southbridge chips have legacy-supporting instances of PIT, PIC, APIC and RTC devices incorporated into their silicon whether or not they are used by the motherboard or the operating system, which is why even a very modern PC can still run older operating systems.The following operating systems are known not to be able to use HPET: Windows XP,[note 2] Windows Server 2003, and earlier Windows versions, Linux kernels prior to 2.6.[note 3]The following operating systems are known to be able to use HPET: Windows XP,[note 4] Windows Server 2008, Windows Server 2008 R2, Windows Vista, Windows 7, x86 based versions of Mac OS X, Linux operating systems using the 2.6 kernel, FreeBSD and OpenSolaris.ProblemsHPET is a continuously running timer that counts upward, not a one-shot device that counts down to zero, causes one interrupt and then stops. Since HPET compares the actual timer value and the programmed target value on equality rather than "greater or equal", interrupts can be missed if the target time has already passed when the comparator value is written into the chip's register. In the presence of non-maskable interrupts (such as System Management Interrupts) that do not have a hard upper bound on their execution time, this race condition requires time-consuming re-checks of the timer after setup and is hard to avoid completely. The difficulties are exacerbated if the comparator value is not synchronized with the timer immediately, but delayed by one or two ticks, as some chipsets do.[4]