Originally posted by Stiletto here:
List of Slowdown Utilities (Beta)

AT-SLOW - AT-SLOW is an alternate slowdown utility that works well on 286, 386, and 486-class machines, utilizing the Real-Time Clock chip found in 286's and above.
http://www.oldskool.org/guides/oldonnew/resou … es/atslo410.zip

Bremze - Bremze (Latvian for 'brake') slows down PC performance by controlling the speed of execution of programs. This feature can be useful when running old processor-dependent programs on new PCs, particularly to decrease the speed of games for 'better results', or when wishing to gain a better understanding of the sequences and functioning of programs, etc. Big diapason of braking coefficients (enough to fastest PCs), braking level control and switch on/off by hot-keys, control output trough PC speeker and screen corner. Full command line control. Slows down DOS and Windows programs. Versions for both interrupts are available - 08h and 70h.
http://ansis.lv/bremze/index.en.php

CPUGrab - The MS DirectShow SDK CPU Grabber utility can be used to slow CPUs down on Win9x - WinXP systems. It features a small slider to control CPU usage. Run it first and then run your game.
http://www.mech2.org/downloads/utils/cpugrab.exe

CPUKiller - CPUKILLER takes the control of your processor and makes the resource occupancy grow enough to slow down the execution of other applications . When you want your computer to return at the normal speed you have only to stop CPUKILLER!.
You can even configure CPUKILLER to launch automatically your old programs and to terminate itself when they exits!
http://www.cpukiller.com/

Delay - This freely distributable program will slow your computer down. Written in the 80's, it may not function well on today's machines. It comes with .asm source, some documentation, and only takes 1k when resident in memory. To change the amount of delay in this program, you must edit and recompile the source.
http://www.geocities.ws/kulhain/delay.zip

DosBox - DosBox is an emulator designed specifically to run MS-DOS games. It emulates a 486 processor so by default it already runs "slow". It also has another use.....as a slowdown utility for other programs. Simply load up seperate instances of DosBox and configure cycles/frameskip for each DosBox session. Each DosBox session will consume host processor cycles just like any other slowdown utility.
http://dosbox.sourceforge.net

ICD/ICE - ICD and ICE disable and enable a 486 or Pentium's internal cache, which can result in a smooth slowdown. Locks up some Pentiums and non-Intel CPUs.
http://www.oldskool.org/guides/oldonnew/resources/icdice.zip

MIPS - MIPS is the speed benchmark Trixter uses when he is trying to get his PC down to a certain speed (and if he uses it, you know it's got the oldskool seal of approval 😉 ). It has "1.0" ratings for a 4.77MHz 8088, 8MHz AT, and 16 MHz 386, so you can gauge how close you are to a certain speed. For example: If you were aiming for an 8MHz 286 and your "number" according to MIPS was 1.7, you'd know that you were too fast and had to slow down your PC a bit more. Conversely, if your "number" after running MIPS was 0.6, you'd know that you slowed down your PC too much and should try again. Just run it and you'll see what he means. Note: This utility reports absolutely wacko results on anything over a 486/66's speed, so if you get numbers that don't make sense, you'll know that your machine is over a 486/66's speed and you need to slow it down further.
http://www.oldskool.org/guides/oldonnew/resources/mips.zip

MoSlo - Mo'Slo is used to slow a specific application or batch file.
http://www.hpaa.com/moslo/

MySLOW - MySLOW is a public domain utility for slowing down MS-DOS games and applications run under Windows 95, Windows 98 and Windows ME.
http://www.csclub.uwaterloo.ca:11068/myslow/

PentSlow - It disables branch prediction and the v-pipeline, maybe even the internal cache. There is one drawback: To speed up the system again you have to reset the machine. Still, any hardware slowdowns are more preferable to software, so it's listed above for your perusal.
http://www.oldskool.org/guides/oldonnew/resou … es/pentslow.com

SLO - This slowdown program (version 1.4) is from Granite Mountain Software and has a $5 shareware fee. It also has an annoying nag-screen delay. It allows you to set the "slowness" of your PC, has an uninstall from memory option, comes with text file documentation, and has several other features. Once installed, it takes up about 1.4k of conventional memory.
http://www.geocities.ws/kulhain/slozip.zip

Slow - Slow is a tiny memory resident program that allow you to use programs that run too fast on your machine by slowing it down. There are several options to change for different values of "slowness".
http://www.geocities.ws/kulhain/slow300.zip

SlowDOS - SlowDOS is a software based slowdown utility, similar to Mo'slo and Bremze that allows you to customize the amount of slowdown in 0.10ms increments. A combination of throttle and SlowDOS should allow you to put any machine down to the good ole 4.77MHz days.
NOTE: SlowDOS requires the use of GIVEIO.SYS, which causes problems for VDMSound.
http://www.oldskool.org/pc/throttle/DOS

SLOWDOWN - SLOWDOWN slows down a fast computer so you can run older programs, or as a troubleshooting aid.
http://bretjohnson.us/

Throttle - Throttle uses your system hardware to modify the clock speed going to your CPU, rather than using software "delay loops" or HLT instructions to slow your machine down. This method provides very smooth slowdowns without any incompatibilies with software.
http://www.oldskool.org/pc/throttle

Turbo - Turbo is a free Windows slowdown utility that lets you slow down your CPU in resource chunks/percentages. It's free, and works pretty well, but lacks many of the advanced features found in shareware Windows slowdown products, like CPUKiller.
http://www.oldskool.org/guides/oldonnew/resources/turbo.zip

Varislow - This slowdown program was written in the 80's, so it may not work well on today's machines. It has user-interactive "slowness" settings - allowing the user to hold down a key to determine how slow they want things to be. After installation, it took only 1k of conventional memory.
http://www.geocities.ws/kulhain/varislow.zip

WHOA! - WHOA! is a memory-resident utility that slows down the computer's execution speed. If you have a superfast AT, AT compatible, or PS/2, you can slow it down to run games and other time-critical programs at a manageable speed.
http://www.geocities.ws/kulhain/whoapc.zip

Sources:
http://www.geocities.ws/kulhain/
http://www.oldskool.org/guides/oldonnew/resources

Things to do:

Categories:

Overall slowdown utility
Application specific slowdown utility
freeware
shareware
GPL
OS specific slowdown utilities
Perhaps list hardware slowdown methods, Lower FSB/Multiplier, disable caches, shadowing, etc.etc.

[EDIT] 2012-27-11 03:52 PM GMT: Added new (old) utilities - Stiletto
[EDIT] 2012-26-11 03:42 PM GMT: Updated Links - Stiletto
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