CHFSB FAQ (1)
Cheepoman and Mpapec

Updated 05/11/02 by Tim B @ OCWorkbench.com

Note : Superseded by Cheepomans Cheepobios’s which include all of the fsb’s available through chfsb and more.

Q1: So what is Chfsb? 

A: The official ECS bios releases for the k7s5a only allow the standard 100 and 133 MHz front system bus (fsb) settings. Some time ago a few beta bioses which included several additional fsb settings were leaked. These are known as the "overclocking" or "OC" bioses. The programming for the extra fsb options is still present in the newer official bioses, but they were removed from the bios menu. Chfsb is a little program that makes it possible to use these extra fsb settings with all bios versions. You can download it here.

Q2: Which are these extra settings?

A: Currently Chfsb supports frequencies of 112/112, 124/124, 138/138, 150/150 and 166/166 (fsb/memory), in addition to the official ones: 100/100, 100/133 and 133/133.

Q3: What bios versions are supported by Chfsb?

All k7s5a bios versions starting from 010724, official and unofficial, are supported and automatically detected

Q4: How do I install/run Chfsb?

A: Chfsb can be run from DOS prompt under win9x/ME issuing "chfsb /i" command which offers multiple FSB speeds. After speed selection you have to reboot your system in order to activate the desired speed. Alternatively, if you prefer more frequent FSB altering chfsb (with full path) can be put on top of autoexec.bat and invoked by holding [shift] key during bootup. Linux/NT/XP users are advised to use it with DOS/win9x startup floppy disk.

Q5: Who wrote it? Is this a commercial program or anything?

A: Chfsb has been developed by Cheepoman and Mpapec, members of the ECS forum at Ocworkbench.com. Other members like cbozo, who had the original idea, udma and many others also contributed. It's 100 percent free for you to enjoy.

Q6: What does the program exactly do?

A: The battery on your motherboard has the only purpose of maintaning the CMOS, which is the small memory area where the BIOS stores its settings. When the computer is powered up the BIOS reads the CMOS contents and then it initializes everything according to these values. The good news is that not only the bios setup utility can read and write the cmos; a number of free utilities, such as cmostool, can do that too. As a result, all bios settings can be modified from outside the bios, if you know what bytes to overwrite and which values to put in. The bios has an internal list of valid values for each setting; some of them are labeled as "reserved" and cannot be selected in the bios setup utility, but they would be accepted anyway if read from the cmos. What Chfsb offers is the possibility of overwriting the fsb related bits with the suitable values for any these "reserved" modes.

Q7: Quite interesting. I would like to know all the details

A: Read here. 

Q8: But, isn't this the same as CPUFSB does?

A: Not quite. CPUFSB directly addresses the PLL, which is the chip that provides the clock signals for the cpu, memory and pci/agp buses. This is nothing but pure overclocking: the pll increases the clock frequency and everything goes proportionally faster. In principle, the Chfsb approach is preferable as all the work is done by the bios, which not only initializes the pll to the desired frequency, but also has the opportunity to set all other internal timings properly. There are some other differences between both programs. CPUFSB allows to change the frequency on the fly, with the computer running. Also, it supports all the frequency settings that the pll can handle, including 142 and 146 MHz. ECS never programmed these modes in the bios, so they cannot be activated with Chfsb. CPUFSB has some problems, though. It hangs most of the time when changing from asynchronous modes (such as 100/133) to synchronous ones (like 133/133). Also, it may hang if to activate the desired mode the pci divider has to be changed (for instance going from fsb=138 MHz pci=34.5 MHz, pci divider=4 to fsb=150 pci=30, pci divider=5). A major advantage of Chfsb is that it doesn't care what operating system you have installed. It will run from the command prompt under win9x/Me, or the win98 compatibility mode of Windows XP. But if you have any other OS all you need is a simple DOS boot disk with Chfsb in it.

Q9: But, booting from a diskette is quite inconvenient. A Win98 boot disk takes ages to load.

A: To run Chfsb you don't need cdrom drivers or FAT32 compatibility. A good old MS-DOS boot disk will do. Please refer to the main k7s5a FAQ on how to prepare a simple boot disk. In addition, you don't need to boot from the floppy all the time. You only need to run Chfsb when you want to change the frequency to a "reserved" value. Once the new frequency is set, it will stay here every time you reboot, just like if you had set it in the bios.

Q10: So after running Chfsb all these new frequencies will be selectable from the bios?

A: No. When you next enter the bios setup utility the fsb frequency will be listed as "reserved". You can change it for any of the official ones (100, 133, 100/133), but then you won't be able to switch back to the unofficial one without running Chfsb again. Please note that you can change anything else within the bios without losing the fsb setting.

Q11: I tried the cmostool method and there were checksum errors or it didn't work at all. Can I use Chfsb?

A: These errors have been corrected. You should have no problem with Chfsb.

Q12: Wouldn't it be easier if someone modified the bios file?

A: Many people in this forum has tried to do so, and the conclusion is that with the tools that we have now, it can't be done. Amibcp 7.53 allows to change many bios settings, but those related to FSB remain hidden.

Q13: Still, perhaps ECS will release a new overclocking bios soon.

A: No way. ECS has stated clearly that there will be no more beta bioses.

Q14: Are you sure I can't damage my bios by using this program?

A: Absolutely. Chfsb does not modify the bios in any way, only overwrites the settings that are stored in the cmos. Although the terms "bios" and "cmos" are sometimes used in a confusing way they are different things. The cmos is just a tiny memory area, 256 bytes (although only 128 are used), and it is not even located in the bios chip, but in the Sis735 chipset.

Q15: I have set the frequency with Chfsb, but on reboot I only get a blank screen

A: Your system can't boot at the specified frequency with your current configuration. Clear the cmos by shorting the corresponding jumper for 30 seconds with the power cord unplugged.

Q16: I have tried 100/133 and performance is lower than with 100/100. What's wrong?

A: Sis 735 is known to be very fast in synchronous mode (when ram speed=fsb speed, for instance 100/100), but it doesn't perform very well in asynchronous mode. Therefore, 100/133 is way slower than 100/100. Similarly 133/166 is slower than 133/133. There is nothing wrong with your particular setup. Just stick to synchronous modes.

Q17: Is FSB overclocking safe?

That depends on how extreme you go. When the multiplier is raised only the CPU is stressed, but with the fsb also the chipset, memory and pci/vga cards have to be considered. For instance, for the pci cards a fsb of 150 MHz (pci=30 MHz) is safer than 147 MHz (pci=37 MHz). Usually components simply won't function if the selected frequency is too high for them, without permanent damage. But this is by no means a general rule. Be careful. In addition, severe overclocking means lots of heat, and heat is more likely to damage components than speed itself. Without proper cooling overclocking should never be considered . Having said that, the k7s5a was never intended to be an overclocker's board, so probably the overclocking that you will get from it will be quite moderate and relatively harmless.

Q18: When I overclock my athlon XP 1600+ to 138 FSB, it is detected as a regular Athlon at 1450 MHz. Is there anything wrong?

A: The bios detects the real CPU speed and then tries to match it with its internal table of CPU models. When your XP is set to 138 FSB (in fact, 137.3), it runs at some 1442 MHz, roughly halfway between an Athlon XP 1600+ (1400 MHz) and a 1700+ (1466 MHz). In the bios table 1450 MHz is a valid Athlon model and this frequency is much closer to your real 1442, so this will be the model selected by the bios to show at boot up. This is just cosmetic. Your CPU should work normally.

Q19: The overclocking bios works fine with me. Should I update the bios and use Chfsb?

A: Only the official bios releases are supported by ECS, and the latest versions have corrected many compatibility issues. However, if you don't need any of these fixes there isn't any reason for you to flash your bios. There is always the possibility that the bios modification that solved some other's problem might create a new one for you. Remember, if it isn't broken, don't fix it.

Q20: I can't possibly boot at 166/166, but I'm convinced my system should be able to. I've modified the board to raise the core, memory and chipset voltages, and lowered the multiplier. I've had moderate success at 166 with cpufsb. What's wrong?

A: Nobody has ever reported being able to boot at 166/166 with a k7s5a board. One possibility is that there be a bug in the bios programming for this mode. Remember, Chfsb only enables what's already programmed in the bios, so it can do nothing if the bios itself has errors.

Q21: 133/166 was present in the 010806 bios. Why can't I select it from Chfsb?

A: We weren't able to test it. If you can boot at 133/166 with that bios please contact us and we'll add it. Later bios versions don't include support for this FSB setting, so it can't be activated.

Q22: Will all the modes work on all bios versions?

A: Not necessarily. Some older bios versions had problems with the 100/133 setting and particular memory configurations, which was solved in a later revision. We cannot discard the possibility that similar issues exist with some of the hidden settings.

Q23: I have a 133 FSB rated processor which won't even boot at stock speed. I'm stuck at 100/100 MHz. How possibly could an overclocking program help me?

A: Most probably you will be able to run at 124/124. It's not perfect, but still it's 24 percent more than 100/100. Please do search the forum for help on your problem.

Q24: I know that the PCChips 830 LR is the same board as the k7s5a. Can I use Chfsb with a PCChips board/bios?

A: The current version of Chfsb doesn't have support for the PCChips board, but it could be easily added if any user would do the testing. Please contact us. In general, using a PCChips bios on the K7s5a is not recommended. While the latter bios versions seem to be ok, there were reports from users that 'fried' their ECS boards with earlier versions of the PCChips bios. Anyway, if you have a specific issue with your board that only a PCChips bios can solve, please contact us and we'll try and find a solution for you.

Q25: Nice program. If only you added fsb frequencies of 142 and 147 and multiplier/vcore settings...

A: Chfsb only allows to activate what already was in the bios. Multiplier and vcore settings were never implemented in the k7s5a bios. The only additional fsb settings that are there but we have not activated are 66/66, 66/100 and 133/100. If someone is interested we could add these to the next version.

Q26: I have tested thoroughly both Chfsb and CPUFSB and the results are rather disappointing compared with other motherboards. The k7s5a is not any good as an overclocking board.

A: ECS just doesn't make extreme overclocking boards, it's not their policy. But in a sense, the k7s5a is one of the better oc-boards out there, since with the money you'll save by buying it instead of some manufacturer's board, you'll be able to buy a much faster CPU. And then you can even overclock it a little bit...Can you ask for anything more? Oh, well, yes. A k7s6a.

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