First post, by aitotat
aitotat
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I made utility to slow down Asus P3B-F motherboard from DOS prompt. It will also work on other motherboards with ICS 9250-08 clock generator and Intel PIIX4/E/M southbridge (most likely all of those use BX chipset). Please let me know if you know some motherboard other than P3B-F that can be used with this utility. I believe it will be a short list but I'd like to know them.
P3B-F Slowdown Utility is meant to be used together with SetMul. Just make sure SetMul is somewhere in PATH and you are good to go.
Here is the readme for instructions:
P3BF Slowdown Utility - Release 1 - 2026.6.9Copyright (C) 2026-2026 by Tomi TilliThis utility is for changing FSB speed from DOS command prompt on systems withAsus P3B-F motherboard. It will also work with other systems that have IntelPIIX4/E/M southbridge (like Intel BX chipset) and ICS 9250-08 clock generatorchip (it is important that it is the same ICS model).P3BF Slowdown Utility can also execute SETMUL.EXE for easier and faster use.SETMUL.EXE must be in the same directory as P3BF.COM or somewhere in the PATH.SETMUL by gerwin can be found at https://www.vogons.org/viewtopic.php?t=38613----------P3BF [parameter(s)] [SETMUL parameter(s)][H or HELP] Prints (this very same) help[UNLK] Leaves Asus P3B-F access to ICS 9250-08 visibleMeant to be used to leave access available for other programs[LOCK] Locks Asus P3B-F access to ICS 9250-08[newFSBclock] Valid clock rates (MHz) for ICS 9250-08 Clock Generator are:66, 75, 83, 100, 103, 105, 110, 112, 115, 120, 124, 133, 140 and 150124 and 133 MHz allow two different PCI divisors:124/3 and 133/3 will divide FSB by 3 for PCI clock (41.3 and 44.3 MHz)124/4 and 133/4 will divide FSB by 4 for PCI clock (31 and 33.3 MHz)Divisor for slower PCI clock will be selected if divisor is not specifiedISA clock is always PCI clock / 4[SETMUL] SETMUL is executed if any of these parameters are set:CPU_MULTIPLIER single number like 4 or 12, also halves like 4.5 or 6.5L1D Disables L1 cache, L1E Enables L1 cacheL2D Disables L2 cache, L2E Enables L2 cache- Below SETMUL parameters are only for VIA C3 CPUs -ICD Disables L1 I-cache, ICE Enables L1 I-cacheBPD Disables Branch Prediction, BPE Enables Branch PredictionImportant!Soft boot (Ctrl-Alt-Del) does not reset FSB speed back to original becauseBIOS only programs the clock generator on cold boot. You should set P3BF.COMto execute from autoexec.bat if you know you are not going to remember toreset the FSB back to fast when you no longer need it to be slow.Known issues:124/3 (124MHz FSB and 41MHz PCI) does not work on my system. Power LED startsto blink and you hear continuous beep from PC-speaker. This is a hardwareissue and not a software bug. Use 124 MHz with 31 MHz PCI instead.
Here is introduction video (and a bit of making of video as well)
