Recently I was looking for a motherboard for a k6-3, and I found it, but the jumper config also could give a fsb of 124Mhz, so could it be possible using the 6.0x get a clock speed of 740Mhz?
Can the k6-3 support a fsb of 124Mhz? if not than what cpu can?
By the way, what limits a cpu's speed?

Although some socket 7 boards had the option to set the FSB at 124MHz, unless there's a way to lock the PCI speed at 33MHz, the board will not run at 124MHz. This is because the PCI speed will jump to 41.33MHz (124/3). If 112MHz is an option, it "should" work because the PCI speed would be 37.33MHz (112/3).

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

Now I understand that fsb-pci speed relation, but where did the /3 come from?
But why a pci bus can't work at higher speeds than 33-37Mhz?
And my original question, could the k6-3 support an overclock up to 740 Mhz?

How high you can go with PCI speeds is a matter of luck of the draw. I've sucessfully run mine at over 42 MHz PCI (FSB 214, 1/5 divisor). Everything worked fine, except my CDRW wouldn't burn correctly. but my 8K3A+ worked great at 209, which dropped the PCI down to just under 42 MHz. I've set up many Socket Seven motherboards using their overclocked bus of 83 MHz. I've yet to have a problem with a harddrive or a PCI card.

No Socket 7 CPU will run at that speed. A K6-2/3+ 550 might hit a little over 600. I've heard reports (but none I'd consider reliable) or hitting around 700 MHz. The .18 micron K6-2/3+ CPUs are the best overclockers of the bunch. But relative to modern CPUs, they are still poor overclockers.

I was able to hit somewhere around 125 FSB (can't remember how high for sure) with a K6-2+ 450 on a GA-5AA. They have settings for up to 140, but you'll never get that high. As it was, I was doing it just to fool around, and I had to go from an AGP to a PCI video card to get a display at that speed.

To figure out what the "PCI divider" is, you just divide the "base" FSB by 33MHz:

66MHz/33 = 2
100MHz/33 = 3
133MHz/33 = 4
166MHz/33 = 5
200MHz/33 = 6

So since you're working with a base FSB of 100MHz, your PCI divider is 3.

If the motherboard has an option to lock the PCI speed at 33MHz, you don't have to worry about the divider. But if that option isn't available, you'll have to take it into consideration when overclocking the FSB. One thing to note is that the AGP is always PCI x 2 (default = 66MHz). On many boards, the BIOS setting will be to lock the AGP speed - this will also lock the PCI.

It's generally recommended NOT to run the PCI speed above 38MHz. IDE devices run on the PCI bus, as well as PCI/AGP devices. If the PCI bus runs too far outta spec, you risk data corruption on your hard drives & errors when using a CD/DVD burner...not to mention problems with PCI/AGP cards. Personally, I use 37.5MHz as my PCI limit.

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

ive successfully ran an ASUS TX97-XE
fully overclocked for about a year and a half until it fully died. i now have it mounted on my wall for fame reasons.
the cpu (350) was at the 83mhz system bus, the 38mhz PCI. the only thing that didnt work was the PCI network card, so i had to use an ISA one.
the fact is, if you can find a socket 7 board with asyncronous PCI, this is what you want, because it wont change with the FSB.
anote to note when you are overclocking socket 7 AMD's, take a flat head screwdriver and pry off the heat spreader, and use a copper base HSF with arctic silver grease inbetween. you can get a more stable cpu if you do this.
with some of the motherboards that do not have a 6x multiplyer, you can sometimes set the multiplyer to 2x on an amd 450 or around there, and it will automatically bump you up to 6x.
another thing, is if you have a board with DIMM slots, put some 133mhz SDRAM in there, and you can put all the ram settings in the bios at the lowest, and you will get no errors!

i hope this helps you, DataX

Several errors in the above response.

At 83MHz FSB the PCI speed would be 41.5MHz (83/2), unless there's an option to set it otherwise.

Popping the heat spreader off the K6-2 is bad advice. The K6-2 doesn't generate enough heat to warrant such a move, plus you risk damaging the CPU. Leave it be.

The 2x multiplier setting will be interpretted as 6x by the K6-2 on ALL boards. This is built into the CPU, not the board.

PC133 will NOT work in most socket 7 boards due to density issues. The RAM timing changes that you may be able to make IF the RAM works, will not make any noticeable performance difference & may cause stability issues.

Is there any wonder why he fried his CPU?

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

Someone might as well tell you the answer you've been anticipating but may not be too happy to hear. NO! you won't be able to run your k6-3 at an overclock up to 740 Mhz.

Even though you have an unlocked multiplier, in reality the PCI bus speed remains your nightmare and you have little control over it. If you care to try the CPU metal plate hack suggested earlier, see how this fella went about getting it done.

B4 you criticize a bigger man, walk a mile in his shoes. That way, you're a mile away, and you have his shoes.

You're right Sabertooth, the question was never answered...LOL.

744MHz (6 x 124) isn't gonna happen, & I doubt 672MHz (6 x 112) will fly either. 600MHz (6 x 100) is a possibility, but chances are, you'll have to set your sights even lower than that.

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

Thanks again jam, good thing that I asked this before doing something.
I have read on some web's, that the k6-3+ 500 can work at 600Mhz with no problem.
And does somebody know how many k6-3+ 500 amd made? Because I'm really having problems to find one. I've only found a k6-2+ 533.

If you can find one, it'd probably cost a good buck. Is it really worth investing a lot of cash in this project? This link was posted about a week ago in a thread about the K6-2, you might wanna check it out:

http://www.aceshardware.com/Spades/read.php?article_id=106

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

As far as I know AMD called those K6-3+ with 500MHz back so there won't be many around to find!

Thanks for the link, I think I'll go for the k6-2+ 533 that I found.

Jam:
the CPU didnot die. it was fine. it was just the motherboard.

i dont risk damaging the cpu when you remove the heat spreader. as long as you're not 'stupid' about doing it. and yes- they do create alot of heat when you are overclocking them.

ive ran 133 on all of my socket 7 boards, and it all worked fine, no memtest errors.

Mr X

"ive ran 133 on all of my socket 7 boards, and it all worked fine, no memtest errors"

I wasn't talking about memtest errors. I was talking about compatibility issues relating to RAM density. My guess is your PC133 was older stuff & probably 64MB or 128MB sticks. In most cases, the PC133 RAM being produced today will not work on systems requiring either PC66 or PC100. I recently ran across the following statement at PNY's website:

"Important Announcement
PC133 Modules are NO LONGER backward compatible with PC100 Machines. To determine the correct memory upgrade for your machine, use the PNY memory configurator."

http://www.pny.com/support/memory/

Asus A7N8X-X
1800+ @ 8 x 210MHz
512MB PC3200
Asus Ti4200 128MB
WinME/WinXP Pro

Older chipsets only "see" half of the capacity of high density RAM. In my experience it works fine otherwise. If PC100 is too hard to find, or too expensive, or if you just happen to have PC133 lying around and don't want to buy RAM, using it and accepting that you only get half capacity is an option. It might be a little wasteful, but so is sinking any kind of real money into these old systems. They are fun to play with, and if you have enough stuff lying around, or given to you for free, you can build good basic systems for those with no computer. Or just to play with, or whatever.

The best place to find the mobile K6 is on Ebay. K6-3+ 450s are plentiful, but can get pricy. The price/performance value chip these days is the K6-2+ 450. I have one in my laptop that will do 550 at default (2.0) voltage. A K6-3+ 550 is fun to think about, but I've recently seen them go for close to $200.00!!

Their prices are a little high, but there is always, http://www.upgradeability.com/K6plus/?source=AdWords1

Your question about what limits CPU speed would be best answered by an engineer. But neither of us might really be able understand his answer!

This article covers some of the basics, http://www.aceshardware.com/Spades/read.php?article_id=50

The big factors seem to be pipelines (basic architecture of the CPU) and the number of transistors. The K6 core seems to be limited to a little over 600 MHz. AMD probably could have came out with a Socket 7 chip based on the Athlon core, but they would have had very little financial incentive to do so. I think the 321 pin interface of Socket 7 would probably hit around one Ghz max (just a guesstimate on my part). AMD, looking to the future, chose to concentrate on a socket interface that gave them plenty of room to grow, the 462 pin Socket A.

But Socket 7 really got AMD's foot in the CPU market door. One of the speculative reasons for Intels abandonment of Socket 7 for Slot 1 was to avoid head to head competition with AMD. Intel haven't let themselves get in a position of using a common CPU interface since then.

Thanks for the link and the info repo man, it really helped to explain some things.