CpuIdle is Copyright (C) 1997, 98 Andreas Goetz.
eMail: cpuidle@gmx.net
Homepage: cpuidle.home.pages.de
CpuIdle's is also the best and most complete CPU optimizer for Win95/98 that exists. Most CPUs include performance increasing options that are disabled by default. CpuIdle activates them all!
Run CpuIdle. If you want to start CpuIdle each time you start Win95/98 open the Options dialog, choose StartUp and check the Start with Windows box. If you are conscious of memory consumption you may want to check Enable Control Panel plugin. CpuIdle will then also start automatically with Windows but consume less memory. The drawback is that you won't get the Idle taskbar icon.
Note: If your Control Panel is missing the "Power Management" folder you won't be able to use the Control Panel plugin. Don't ask me how to get the "Power Management" folder- I don't know.
Under normal circumstances the CPU isn't always active but spends much time waiting for the keyboard, harddisk or CD-ROM. What would be more logical than to turn off the CPU for that period? That's exactly what the HLT machine instruction (Opcode F4) does. Whenever the CPU encounters a HLT instruction the clock is halted and the CPU enters suspend mode until an interrupt, NMI, or reset happens. With the advent of power saving microprocessors like the Cyrix Cx486S the HLT instruction elicits an additional benefit. When "Suspend on HLT" is enabled in the configuration register the processor not only stops on HLT but also enters the power saving suspend mode.
Modern operating systems like Linux or Windows NT execute the HLT instruction in an idle priority thread. This thread is always executed when, as the name implies, the CPU is otherwise idle. Therefore no additional execution time is needed, the CPU will not run slower. This does not hurt performance since the CPU controls the powering-down of specific internal parts by hardware-control, so there's no software intervention needed for explicitly re-enabling a powered-down part (cited from set6x86 readme by Koen Gadeyne).
Using this feature the power consumption at the Windows NT prompt can be- according to German c't magazine- 2.1A (K6-166) to 5.3A (K6 233) lower than at the DOS prompt. With Intel processors the power saving is lower but also measurable. For Cyrix the "Suspend on HLT" feature must first be enabled if the BIOS does not provide support. That can be done with tools like cx86 from www.heise.de/ct/ftp or set6x86.
Unfortunately, Windows 95 does not support HLT. To remove this limitation CpuIdle provides an idle thread executing HLT for Windows 95. Since HLT is a privileged instruction it can only be executed on ring 0 whereas normal Windows programs run on ring 3. CpuIdle uses a virtual device driver (VxD) that can run on ring 0 to execute HLT.
On the test system (K6-200) the temperature as measured below the fan could be lowered by more than 10 degrees centigrade when Windows was idle.
| Intel P5/P5MMX |
Intel P II |
AMD K5/K6/K6-2 |
Cyrix M1SC/M1/M2 |
IDT C6 |
|
| Write Allocatation* | Yes | Yes | |||
| Auto HLT (AHD)* Low Power on AHD* Suspend on HLT* |
Yes Yes (MMX only) |
Yes | Always On |
Yes |
Yes |
| No Locking* | Yes | Yes | |||
| Weak Ordering* | Yes |
* If a given feature exists on a CPU it will be enabled by default. If you experience problems with this please read the next section on how to disable the features you don't need.
If started without any parameters CpuIdle will consume about 500KB of 32Bit memory (according to Wintop from MS Kernel Toys). The largest part of this memory is used for the nice interface, icons and bitmaps. If you think that this is too much and you don't need the interface you should use the Control Panel plugin.
For Cyrix CPUs further information is displayed, like Write Allocation or Suspend on HLT (if you see that this is disabled CpuIdle can't do much good for your Cyrix based system).
Even if Windows has identified your CPU as "CyrixInstead" (also via CPUID), Windows obviously first enables CPUID, executes the instruction and then disables it again (at least in OSR2). Unfortunately enabling is a privileged instruction and only allowed for the system. Maybe later releases of CpuIdle will address this problem.
If your CPU is not or not correctly identified by CpuIdle, or the displayed clock rate is incorrect, CpuIdle's main function, the cooling of your CPU, is NOT impaired.
CpuIdle knows just one parameter, which is -hide. With this parameter CpuIdle is loaded without displaying the taskbar idle icon. The drawback is that if you want to exit or restart CpuIdle you'll first have to kill the program manually since there's no hotkey available to redisplay the icon. The CpuIdle display can also be hidden by selecting "Hide" in the CpuIdle menu.
| AMD | CpuIdle should work instantly with AMD Microprocessors K5, K6, K6-2 and upcoming K6-3 (or K6 3D+ or whatever it is called). All AMD CPUs have built-in "Suspend on HLT" that is always enabled. |
| Intel |
Modern Intel P5, P5MMX, PPro and PII type processors are supported. With the P5 Intel introduced "Suspend on HLT" for it's CPUs. This features is hardly documented and by default disabled (shame on all BIOS programmers). To my knowledge CpuIdle is the only software that uses this feature. When this feature is enabled additional 1.8 Amperes can be saved. Without enabled AutoHalt (that's how it's called) Intel CPUs will still run cooler with CpuIdle but from the table below you can see that the power (and temperature) savings will be lower than for AMD or Cyrix processors (these values are taken from c't magazine without AutoHalt enabled). Note: AutoHalt means the same like "Suspend on HLT" |
| Cyrix | Cyrix M1SC, M1 and M2 have a "Suspend on HLT" feature that has to be enabled by software or via BIOS setup. When run without command line switches that override the default settings CpuIdle enables "Suspend on HLT" by default. With the same procedure it should also work with 486 Cyrix, TI and IBM models. |
"Suspend on Halt" for Cyrix compatible CPUs:
The following processors should all be supported by CpuIdle if the "Suspend on Halt" (Bit 3 in Configuration Control Register 2 - CCR2) is enabled. CpuIdle enables this feature by default.
Cyrix: Cx486S/S2/D/D2/DX/DX2/DX4
Cx5x86 (M1SC), Cyrix Cx6x86 (M1), Cx6x86MX (M2)
IBM: BL486DX/DX2 (Blue Lightning)
5x86, 6x86
TI: TI486DX2,TI486DX4
| AMD | K5-166 | K6-166 | K6-200 | K6-233 |
| DOS | 5.2A | 3.8A | 5.0A | 7.2A |
| NT | 2.8A | 1.7A | 1.8A | 1.9A |
| Intel P5 | 166 | MMX-166 | MMX-200 | MMX-233 |
| DOS | 5.1A | 3.94A | 4.4A | 5.2A |
| NT | 4.2A | 3.25A | 4.2A | 4.9A |
Q: Ok, I believe that CpuIdle works, but is it safe?
A: Well, Win NT does is, Linux does it and OS/2 does it. However a cheap PC with low-quality components could possible be crashed by CpuIdle, as well as by any other application.
Q: Does CpuIdle put additional load onto my CPU?
A: Read the documentation. No. It just consumes idle time. Measurements with the Winstone benchmark suite have shown that CpuIdle does not decrease the system performance.
Q: But my CPU monitor suddenly shows 100% CPU load. How can this be?
A: The monitor measures how much idle time it receives, and it won't get any since this time is spent in suspend mode. This does not affect normal applications.
Q: Now. You just said that with CpuIdle the System Monitor shows 100% CPU usage when CpuIdle is running (and working). It doesn't on my system. Is CpuIdle not working?
A: You're probably using the Control Panel plugin provided with CpuIdle 3. When this plugin is enabled, CpuIdle is run just once (during startup) to optimize your CPU, load it's driver (the mysterious VxD) and the quits again, leaving the VxD in memory. Due to this fact the VxD is no longer owned by any program who's name could be shown by the CPU monitor or similiar tools (due to the way these things are implemented). CpuIdle is still working.
If you use the plugin please make sure you see the splash screen at startup to veryfy that the program was started.
Q: When I run CpuIdle my computer immediately crashes/ GPF's/ reboots. What's going on?
A: I honestly don't have the slightest idea. Sorry.
Q: When I run CpuIdle I get random reboots every 10 to 60 minutes. Can you help?
A: No, I'm sorry. Very few people have reported this. Most of them use VX chipsets. I don't know if this is an incompatibility. It could also be (with VX chipsets slightly out of fashion) that these computers use power supplies with an out of date design which isn't living up to the motherboard's and CPU's current expectations.
Q: When I run CpuIdle my fan turns slower and the voltage on the +5V and +12V lines decreases. Doesn't that mean that the CPU is drawing more power?
A: No. Most computer power supplies only compensate higher power demands on the +5V rail, resulting in an increase on the +12V rail when +5V power demand goes up.
Koen Gadeyne says in the readme for set6x86:
"The CPU draws from the +5V rail, but the CPU fan uses +12V, so when the CPU draws more power (due to CPU load), the CPU cooling fan (which is delivered with the CPU by Cyrix) will run a little faster with higher supply voltages, so the significant power drop when the CPU drops into power-suspend mode might cause a noticeable change in the pitch of the buzzing fan sound!"
It depends on the way the switching power supply is designed. The 12V are generated in the same switching transformer as the 5V, and just the 5V is regulated. This means that the 12V voltage will depend on the current
flowing by the transformer primary winding. What happens is that when CpuIdle runs, there is less +5V current so the switching power supply sends less current across the transformer primary and therefore the 12V MUST
decrease as the feedback regulation loop exist only in the +5V. That's the reason behind the "fan mystery".
Q: When I run CpuIdle I hear terrible static noise or buzzing sound through the speakers attached to my soundcard. What's up?
A: This problem can probably be pinned on a poorly designed power supply and/ or soundcard. I can't help you with that, sorry.
Q: How can I use the command line switches?
A: Make a shortcut to the program, right mouse click on the shortcut, go down and click on properties, select the shortcut tab, you can add the switches where it says target. After you have verified that the shortcut works, it is recommended to copy it to your StartUp folder.
Q: CpuIdle says "CPUID instruction not available on this machine". What does this mean?
A: This means that your CPU either doesn't have the CPUID machine instruction (like 486 CPUs) or that it isn't enabled. On Cyrix CPUs CPUID can be en/disabled. Normally the BIOS should enable CPUID but on some machines it doesn't. If you have a Cyrix CPU and want to enable CPUID you can use tools like set6x86 to do this. Without CPUID CpuIdle will not be able to determine the clock rate of your CPU. However this does NOT influence other CpuIdle functions.
Q: When I use DosIdle for DOS sessions, should I need to use CpuIdle when I enter Win95? Will it conflict if I use DosIdle in DOS and CpuIdle in Win95?
A: CpuIdle is designed to HLT under Win95/98. It works under a Windows DOS Box as well, but is inefficient with ill-behaving DOS programs like Norton Commander (with these programs in a DOS window you can usually feel your other Windows programs run slower). DosIdle should work under older MS-DOS versions (MS-DOS up to 6.2), Windows DOS Box and MS-DOS 7.00 and above (if you restart in MS-DOS mode from Win95/98).
To have DosIdle enabled all the time, just install it to your Win95/98 Autoexec.bat AND the DOS 6.22 (or below) Autoexec.bat. This way, DosIdle will take care of anything that's DOS related. And it doesn't conflict with CpuIdle!
Q: When I start CpuIdle on my 486 notebook it crashes with a "Fatal Exception 0D in VXD CPUIDLE". What can I do?
A: CpuIdle didn't recognize your CPU and tried to use unsupported features. Please start CpuIdle with the -noopt command line switch.
Q: Not all CPU features are enabled on my new PII CPU -- what's up?
A: I don't have access to a PII machine and couldn't do any testing but it seems as if some PII CPUs don't support all features.
The easiest way is cash payment. You can put $20 into an opaque envelope (perhaps add some dark paper) and address it to me. German users can also transfer the money directly to my bank account as given below (do NOT forget your Name and EMail address and send me a notification via email!)
If you want to pay via check, money order or credit card please use the included register.exe program. Note: The register.exe program cannot be used for payments in German currency.
For multi-user, site- and world-wide licenses, please see contact me directly.
Address: Bank Account: Andreas Goetz Name: Andreas Goetz Südring 11 Bank: Kreissparkasse Hannover 31275 Lehrte BLZ: 250 502 99 GERMANY Account:1100638152If you read the documentation carefully and still have questions you can reach me at cpuidle@gmx.net. Please make sure that you read the Frequently Asked Questions. Most points are already covered there.
Thank You!
Muddle who proof-read this document and first aroused my love for the English language.
Virgil Smith for coding the VxD. Without him this program would never have been possible.
Marton Balog for his friendship and his enthusiasm in coding DosIdle.
Simon Capwell for the great Control Panel idea and programming.
Daniel Nelson for help in Windows 98 troubleshooting and further proofing of this web page.
Alex van Kaam for is help with the numeric tray icon and MBM.
Kamil Huseyinoglu for is valuable assembler and debugger advice.
Geoff Chappel for his hints in comp.os.ms-windows.programmer.vxd.
More thanks to the following authors for their Freeware Delphi components:
Ahto Tanner (TUrlLabel)
Pete Ness (TTrayIcon)
...and all other people who encouraged me in the development of this program with appreciation, suggestions and helpful criticism.