CPU Identification utility

CPU Upgrade:
How to easily check your CPU Vendor, Model,
Internal speed, and L1 cache mode settings.

by Jan Steunebrink
Last updated on July 7, 2008

Introduction

After a CPU and/or motherboard upgrade, it can be difficult to find the correct motherboard jumper or BIOS settings for clockspeed, clock multiplier, and (for 486 only) internal cache Write-Back/Write-Through mode selection.
I wrote a utility, called CHKCPU, to have an easy check on these settings.
On the other hand, CHKCPU is also useful for checking the CPU type and speed on a given machine and, due to its text-based output, information from CHKCPU can easily be used to get CPU info from each machine in a network by calling CHKCPU from the network log-on script.

CHKCPU comes in two flavors, a DOS version and a Win32 console mode version. I've named the Win32 version CHKCPU32 to distinguish it from the DOS version. Both versions give approximately the same text-based output.
You can download both programs here and in each zip a text-file is included with more information about the program and the changes I've made in this revision.
DOS version: CHKCPU v1.15
Win32 version: CHKCPU32 v2.03
Both programs are dated 07/07/2008, have the same update status regarding the CPU model data, and they are both freeware.

The programs

CHKCPU can be run from the DOS prompt or from a DOS-box within Windows. CHKCPU is designed to run under DOS 5.0 or higher, or any version of Windows. For most CPUs however, the Clock multiplier and Bus clock speed can only be indicated in 'Real mode' DOS.
CHKCPU32 is designed to run in the command window of any 32/64-bit Windows version (Win95 or higher). Because CHKCPU32 is a true Windows program, it gives a better speed indication accuracy on high speed CPUs than the 16-bit CHKCPU when run under Windows. This is especially true under WinNT4/2K/XP/2003/Vista/2008.
In addition, CHKCPU32 can display the number of CPU cores in a system.

Main differences between CHKCPU and CHKCPU32
Feature CHKCPU CHKCPU32 Remarks

Support for DOS Yes No

Support for Windows Yes Yes, Win95 or later CHKCPU32 has better speed indication accuracy under WinNT4/2K/XP/2003/Vista/2008.

CPU support 386 and up 586 and up Support for NexGen and UMC CPUs has been dropped from CHKCPU32.
Use CHKCPU if 386/486 or NexGen support is needed.

Multiplier/FSB support Yes, but only in Real mode DOS Not yet Will be added in a later version of CHKCPU32.

Dual/Multi CPU support No Yes

L1 Cache Mode indication Yes No As this indication lost its meaning on modern Pentium class CPUs, it has been dropped from CHKCPU32.

On my upgraded 586 PC, CHKCPU displays the following information:

**Main differences between CHKCPU and CHKCPU32**
Feature	CHKCPU	CHKCPU32	Remarks
Support for DOS	Yes	No
Support for Windows	Yes	Yes, Win95 or later	CHKCPU32 has better speed indication accuracy under WinNT4/2K/XP/2003/Vista/2008.
CPU support	386 and up	586 and up	Support for NexGen and UMC CPUs has been dropped from CHKCPU32. Use CHKCPU if 386/486 or NexGen support is needed.
Multiplier/FSB support	Yes, but only in Real mode DOS	Not yet	Will be added in a later version of CHKCPU32.
Dual/Multi CPU support	No	Yes
L1 Cache Mode indication	Yes	No	As this indication lost its meaning on modern Pentium class CPUs, it has been dropped from CHKCPU32.

 CPU Identification utility v1.15                 (c) 1997-2008 Jan Steunebrink
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 CPU Vendor and Model: AMD K6-III+ 450/475/500/550
 Internal CPU speed  : 601.2 MHz  (using internal Time Stamp Counter)
 Clock Multiplier    : 6.0 
 Bus clock speed     : 100.2 MHz
 CPU-ID Vendor string: AuthenticAMD
 CPU-ID Name string  : AMD-K6(tm)-III Processor
 CPU-ID Signature    : 0005D0
                       |||||+- Stepping or sub-model no.
                       ||||+- Model: Indicates CPU Model and 486 L1 cache mode
                       |||+- Family: 4=486, Am5x86, Cx5x86
                       |||           5=Pentium, Nx586, Cx6x86, K5/K6, C6, mP6
                       |||           6=PentiumPro/II/III, CxMII/III, Athlon, C3
                       |||           F=Pentium4, Athlon64
                       ||+- Type: 0=Standard, 1=Overdrive, 2=2nd Dual Pentium
                       |+- Ext. Model: Extends the Base Model to an 8-bit value
                       +- Ext. Family: Extends the Base Family value
 Current CPU mode    : Real
 Internal (L1) cache : Enabled in Write-Back mode

Apart from this 'Normal' display, CHKCPU supports command-line switches to get another format or to display additional CPU information.
You can get a list of these switches with the command CHKCPU /? or /H
The following switches are supported:

With CHKCPU /C you get the CPUID only mode. In this mode, any code that does more than CPUID data processing, like speed measurement, is skipped. So this mode works like a safe detection mode and can be used for troubleshooting problems when using CHKCPU.
With CHKCPU /D you get the Debug mode. It displays a dump of raw OS and relevant CPUID level information. Great for troubleshooting "Unknown" indications or getting info on new CPU models.
With CHKCPU /F you get the Frequency mode. It displays the CPU Speed only. Intended for use in scripts, to allow decision making based on speed. The output is in MHz but has no trailing 'MHz' indication.
With CHKCPU /I you force the use of the Instruction timing method for CPU speed measurement. Useful if the TSC method gives an incorrect reading.
With CHKCPU /R you force the use of Real (or Virtual) mode. Protected mode via the DOS Protected Mode Interface is then not used.
With CHKCPU /S you get a Short display of CPU Type and Speed only. Intended for use in network logon scripts. The output has no trailing CR.
With CHKCPU /V you get the Verbose mode. It displays additional CPUID info like CPU features and the sizes of the L1 and integrated L2/L3 cache. For CPUs with split Data/Instruction L1 caches, the combined value is shown.
Some CPU features are only displayed for specific CPUs.
The CPU features and the size of the caches, are all derived from the CPU-ID information.
Note that on Multi-Core CPUs the sizes of the L1 and L2 cache are indicated for one core, unless a combined L2 cache is used by the CPU in question. In the later case, the total L2 cache size of the CPU is indicated.
A L3 cache, if present, is usually a combined cache.

Switches can be combined. Example: CHKCPU /S /C gives a short display of the CPU type only. The speed is not displayed.
Except for the /I and /R switch, CHKCPU32 supports the same switches.

On my Celeron M laptop, running Windows Vista, CHKCPU32 /V shows:

 CPU Identification utility v2.03                 (c) 1997-2008 Jan Steunebrink
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 CPU Vendor and Model: Intel Celeron M 410/420/423/430 C0-step
 Internal CPU speed  : 1729.0 MHz
 Number of CPUs      : 1
 CPU-ID Vendor string: GenuineIntel
 CPU-ID Name string  : Intel(R) Celeron(R) M CPU        430  @ 1.73GHz
 CPU-ID Signature    : 0006E8
 CPU Features        : Floating-Point Unit on chip: Yes
                       Time Stamp Counter         : Yes
                       MMX instruction set        : Yes
                       3DNow! instruction set     : No
                       Streaming SIMD Extensions  : Yes
                       SSE2 support               : Yes
                       SSE3 support               : Yes
                       Hyper-Threading Technology : No
                       Execute Disable protection : Yes
                       64-bit support             : No
                       Virtualization Technology  : No
 Size of L1 cache    : 64 KB
 Integrated L2 cache : 1024 KB
 Integrated L3 cache : None

CHKCPU32 /V under WinXP on my Athlon XP (Barton) box looks like:

 CPU Identification utility v2.03                 (c) 1997-2008 Jan Steunebrink
 覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧覧
 CPU Vendor and Model: AMD Athlon XP 2000+-3200+
 Internal CPU speed  : 1833.1 MHz
 Number of CPUs      : 1
 CPU-ID Vendor string: AuthenticAMD
 CPU-ID Name string  : AMD Athlon(TM) XP 2500+
 CPU-ID Signature    : 0006A0
 CPU Features        : Floating-Point Unit on chip: Yes
                       Virtual Mode Extensions    : Yes
                       Time Stamp Counter         : Yes
                       MMX instruction set        : Yes
                       3DNow! instruction set     : Yes
                       Streaming SIMD Extensions  : Yes
                       SSE2 support               : No
 Size of L1 cache    : 128 KB
 Integrated L2 cache : 512 KB

CHKCPU recognizes any 386 or higher CPU, however detailed information can only be displayed for CPUs which support the CPUID instruction or Cyrix CPUs with Device Identification Register (DIR) support. This covers some 486 and all 586/Pentium and higher CPUs.
CHKCPU recognizes CPUs from Intel, AMD, NexGen, Cyrix/IBM, UMC, IDT, VIA, Rise, and Transmeta.
If the program is run on a 386 or (non-Cyrix) 486 CPU without CPUID support, the CPU will be indicated as a 'classic' 386 or 'classic' 486 and a shortened display with only speed and (if present) cache information will follow.

CHKCPU32 is meant to be used on 586/Pentium or higher CPUs only. CPUs which do not know the CPUID instruction are not supported by CHKCPU32. In addition, CHKCPU32 relies solely on the TSC for CPU speed measurement.
CHKCPU32 recognizes CPUs from Intel, AMD, Cyrix/IBM, IDT, VIA, Rise, and Transmeta.

Clock multiplier and CPU speed

Since the Intel 486DX2 hit the market, most CPUs run internally faster than externally.
The Internal CPU speed display indicates the true internal CPU clock speed.
The internal CPU clock speed = Bus clock X Clock multiplier.
The Bus clock is the speed of the motherboard clock.
On Pentium class CPUs, the multiplier factor is usually selectable in steps of 0.5 (x1.5, x2, x2.5, x3 etc.).
Some CPUs have a fixed multiplier factor (Celeron, PentiumIII/4), and some use fractional factors like x1.75 (K5) or x2.33 (Winchip-2A).

Most CPUs provide data on which Clock multiplier setting they are running. CHKCPU will display the Clock multiplier when available, and also calculate and displays the Bus clock speed in this case.
Note that the classic Pentiums, like the Intel Pentium I, Pentium MMX, and AMD K6 do not provide any clock multiplier data.

For Intel CPUs the internal speed equals the rating. So a Pentium 200 will run internally at 200 MHz. (66.6 x 3)
For AMD, Cyrix, and Rise CPUs the internal speed can be lower than the PR rating due newer and more efficient design.
For the K6-2 and later AMD CPUs upto 1400MHz, the internal speed equals the rating but modern CPUs use a performance figure as rating.

CHKCPU measures the CPU speed by accurately timing the execution of a bunch of slow 'Divide' instructions.
For Pentium class CPUs however, the internal Time Stamp Counter (TSC) is used whenever possible to further improve the accuracy of the speed measurement.
A message behind the CPU speed display indicates if the TSC is used.
As using the TSC would crash CHKCPU when the CPU is in 'Virtual mode', the CPU speed measurement switches back to the (less accurate) instruction timing method when the CPU is not in 'Real or Protected mode'.

CHKCPU32 measures the CPU speed by accurately timing the increment of the CPU's internal Time Stamp Counter (TSC). As a timebase, the Windows own PerformanceCounter is used which in turn is based on one of the motherboard's hardware timers.

Other display details

The CPU-ID Name string is only displayed when supported by the CPU. This name string is stored in the CPU and is usually programmed into the CPU by the manufacturer or by the BIOS at boottime.

CHKCPU32 only:
The Number of CPUs display indicates the number of 'logical' CPU cores as detected by Windows. Without Hyper-Threading, this number is equal to the number of physical CPU cores. But with Hyper-Threading enabled, the indicated number of logical cores can be double the number of physical cores.

Internal (L1) cache

CHKCPU only:
The program detects if the internal (Level 1) cache is disabled or enabled.
If enabled, the program indicates if the cache operates in the Write-Through (read only cache) or Write-Back (read and write cache) mode.
For the 486 CPU family, this information is derived from the CPU-ID signature.
For Cyrix 486/5x86 CPUs, configuration control register #2 (C2h) bit 1 supplies this information.

The Pentium and higher CPU families normally operate their L1 cache in Write-Back mode.
Exceptions are: the Nx586, the Intel Pentium 63/83 ODP (P24T) and the Cyrix 6x86/6x86MX/MII.
The Nx586 has only Write-Through mode and is indicated as such.
The P24T can operate in either the Write-Through or Write-Back mode. For this CPU, CHKCPU uses a special routine to detect the difference.
The Cyrix 6x86 series usually operates in Write-Back mode but can be switched to Write-Through mode by enabling CR0 bit 29 (NW - No Write-back). CHKCPU checks this bit and displays the L1 cache mode accordingly.
For all other Pentium class CPUs, CHKCPU assumes Write-Back mode.

Acknowledgments

I could not have written these programs without the hard work of these people:

Christian Ludloff http://www.sandpile.org/ for his unsurpassed amount and detail of CPU information.
Grzegorz Mazur http://grafi.ii.pw.edu.pl/gbm/x86/ for publishing the basic algorithms for CPU detection.
Frank van Gilluwe, author of "The Undocumented PC" (second edition); still my favorite hardware book. The internal CPU speed detection routine according the instruction timing method is based on ideas from his book.
Steve Hutchesson www.masm32.com for providing the MASM32 package. This Win32 MASM package allowed me to port the DOS-based CHKCPU to the Win32 platform relatively easy. However some procedures, like the CPU speed detection, had to be rewritten completely. ;-)
(Yes, both CHKCPU and CHKCPU32 are written in assembler!)

Feedback requested

If you encounter an "Unknown" message, please send me an E-mail with your CPU details and the CHKCPU /V and CHKCPU /D outputs.
You can use this REPORT.BAT file to collect the CHKCPU(32) outputs. This batch-file works both under DOS and Windows. It can log outputs from either CHKCPU or CHKCPU32 and stores it in a MYCPU.TXT or MYCPU32.TXT file respectively. Just place REPORT.BAT in the same folder as CHKCPU(32).EXE and run it.
Alternately, you can use DOS's redirect and append functions to get the outputs in a file.
E.g. CHKCPU /V > MYCPU.TXT and CHKCPU /D >> MYCPU.TXT
or CHKCPU32 /V > MYCPU32.TXT and CHKCPU32 /D >> MYCPU32.TXT

Any comments? Please send a message to J.Steunebrink@net.HCC.nl

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CPU Upgrade: How to easily check your CPU Vendor, Model, Internal speed, and L1 cache mode settings.