You'd need a multiplier of 8.25x to get 550 from 66, and I don't recall seeing this. I tried to find a list of multipliers for that CPU but found only an incomplete list. Even a 75MHz FSB would need 7.33x, and 83MHz x6 is only 400MHz. I think you just have to set the highest multiplier you have available and use that with 66MHz FSB. Your BIOS may not support detecting the frequency correctly if it does not understand the CPU.

I'm pretty sure that 6x is the largest possible multiplier for K6-2/3(+) CPUs. So if you stick to 66MHz FSB you'll get 400MHz.

If you'd like more performance you could get a K6-3(+) with integrated L2 cache. Of course I don't know which models might work with your MB.

Get one of these:

http://www.ebay.com/itm/CPU-PROZESSOR-AMD-K6- … =item2ec84d8ec6

PS: I'm not the seller, i got one from him, it's brand new and it's the fastest SS 7 CPU you can get.

OK, lets get it straight here.

Yes, since a K6 chip already is installed in your motherboard, chances are VERY high that a AMD K6-2 will work. Even though the intended CPU speed is 100mhz FSB, running it on 66mhz FSB will not be a problem. You are just limited to 400mhz (6x66). From the link you provided your motherboard runs on the 430VX chipset which to my knowlegde never provided a 100mhz FSB option. It could be possible it can run at 75mhz or 83mhz FSB, but don't count on that since it is from Compaq.

Other people in this thread recommends the AMD K6-3+, but be careful with this CPU. It is made to run at 1.6V (but can be run at higher volts) and from what I've read, many motherboards that supports the AMD K6-3 2.4V does not support the + version unless there is a BIOS update available. My Compaq (also based on the Intel 430VX) runs with the AMD K6-3 in a Powerleap adapter and the performance increase is huge compared to a AMD K6-2 (which I used previously).

Multiplier settings are pretty basic. The 2x setting will equal 6x for the CPU, so just do this.

I also have to put out a warning against the seller carlostex linked to. He never replied to any of my messages in both English and German. I don't trust sellers who never replies.

vetz wrote:

Other people in this thread recommends the AMD K6-3+, but be careful with this CPU. It is made to run at 1.6V (but can be run at higher volts) and from what I've read, many motherboards that supports the AMD K6-3 2.4V does not support the + version unless there is a BIOS update available. My Compaq (also based on the Intel 430VX) runs with the AMD K6-3 in a Powerleap adapter and the performance increase is huge compared to a AMD K6-2 (which I used previously).

K6-3+ is usually rated for 2.0V. The model carlostex linked to is an embedded ATZ version which is indeed rated for 1.6V@400MHz. 2.0V should be no problem since the die is not really different, same 0.18µ process.
The advantage of the + models is that they use less power, the normal K6-III cpus run rather hot.
BIOS support can indeed be a problem, especially with such an OEM board. But according to http://web.inter.nl.net/hcc/J.Steunebrink/k6plus.htm you can get everything working without BIOS support as well.

vetz wrote:

Multiplier settings are pretty basic. The 2x setting will equal 6x for the CPU, so just do this.

Correct, I should have written that.

vetz wrote:

I also have to put out a warning against the seller carlostex linked to. He never replied to any of my messages in both English and German. I don't trust sellers who never replies.

I bought an identical CPU from that seller in 2009.

Thank you for helping with my upgrade plan. I have more questions.

To begin with, here's some more specific information on my Presario 2255's motherboard: http://www.elhvb.com/mobokive/Archive/Compaq/ … 5sbjumpers.html

This motherboard has an Intel SB82437VX chip.

This is an old Socket 7 (not Super Socket 7) board, and according to the above link the board has 2.2 volts core voltage. Does this voltage cause a problem with the K6-III chip? Do I need any sort of a Powerleap adapter?

And, I assume whether I go with the K6-2 or the K6-III, I would leave the multiplier pins on my motherboard in the same position as they are now (with my current K-6 300 MMX chip), correct?

My main purpose is to upgrade my system to 3DNow and give it the fastest processor speed...consistent with stability, and not an overly complicated installation. I still don't know for sure whether that means I should get a K6-2 (some of which have a FSB 66) or take the leap to K6-III (I think I've ruled out the "+" versions due to possible motherboard incompatibilities).

PS: Essentially, what I would like to now know, is which exact K6-III chip will be the fastest one that is likely compatible with my motherboard? (I think some of the K6-III were designated FSB 66, so is one of those preferable for my system, versus the FSB 100 versions?)

What's the maximum voltage u can run a k6-2 processor?
I have an A-Trend ATC5000 motherboard,with intel tx chipset,minimum voltage setting is 2,7,k6-2 needs 2.2,so that's a 0,5 voltage difference,will it fry the k6-2?

Nahkri wrote:

What's the maximum voltage u can run a k6-2 processor?
I have an A-Trend ATC5000 motherboard,with intel tx chipset,minimum voltage setting is 2,7,k6-2 needs 2.2,so that's a 0,5 voltage difference,will it fry the k6-2?

I don't know much about these, but from what I've read online, it looks like a 2.7 core voltage is way too high for the K6-2 processors.

From your link to the motheroard's specs, 2.2v is supported.

Here's a link showing the K6-2 550 volatge as 2.2v.

Yes, you can install the 550 K6-2 CPU on this motherboard but can only run at it's max 300MHz due to the multiplier restriction on that board. I am not sure if there are undocumented jumper settings to increase the multiplier.
(One of my previous SS7 board had an undocumented voltage selection feature.)

But there shouldn't be any problems running it.

I used to run a K6-2 500 (or 450MHz, crc) at 133MHz on a SS7 board. (Multiplier at 66MHz X 2).

Malik wrote:

From your link to the motheroard's specs, 2.2v is supported. […]
Show full quote

From your link to the motheroard's specs, 2.2v is supported.

Here's a link showing the K6-2 550 volatge as 2.2v.

Yes, you can install the 550 K6-2 CPU on this motherboard but can only run at it's max 300MHz due to the multiplier restriction on that board. I am not sure if there are undocumented jumper settings to increase the multiplier.
(One of my previous SS7 board had an undocumented voltage selection feature.)

But there shouldn't be any problems running it.

I used to run a K6-2 500 (or 450MHz, crc) at 133MHz on a SS7 board. (Multiplier at 66MHz X 2).

I'm hoping I can maybe even run a K6-III at an effective 400MHz or better...but I'm not sure which particular processor would be best to try (I thought I saw somewhere that maybe some of the K6-III processors offered 66 FSB compatibility....but I'm not sure that's right).

No such thing as "66 FSB" compatibility. They all will run on lower FSB.

All the AMD chips have the Core voltage written on the front. Embedded versions are super low at 1.6V and need a mainboard like the Gigabyte 5AX. And you usually need the latest BIOS version which can be tricky with your OEM board.

The K6-2 and 3 plus allow changing of the multiplier through software. But ultimately 400MHz will be top of the ceiling for you.

Mau1wurf1977 wrote:

The K6-2 and 3 plus allow changing of the multiplier through software. But ultimately 400MHz will be top of the ceiling for you.

Yes, it looks like a "regular" K6-III is my best chance for compatibility.

Thanks for the help everyone ! 😀

Good luck in your search for a non plus AMD K6-III 😀 If it works you'll see some very nice performance increase

No need to search! There is a German seller who has a TON of these chips. However, it's the embedded version with 1.6V Vcore. I ordered two, just for giggles and my 5AX supports the low voltage. It means you can run this chip passive with a decent cooler slapped onto it.

Here is the link:

http://www.ebay.com.au/itm/AMD-K6-III-400-ATZ … c8570d03&_uhb=1

Maur1wulf: Several times it has been stated that the + version is less compatible with motherboards, which means he takes a larger risk buying that embedded plus version.

Also the seller is not professional is my impression. (does not answer questions)

Mau1wurf1977 wrote:

No need to search! There is a German seller who has a TON of these chips. However, it's the embedded version...

Yeah, thanks for the input, Mau1wurf...but due to lots of reports of motherboard incompatibilities, I'm going to wait for the "regular" K6-III version for my upgrade. Of course, no guarantees with that one, either -- but it looks like the odds are a bit better. 😀

If it is of any help, I bought 3 of these processor long ago from this seller. In GA-5AX boards (rev 4.1 and 5.2) these ATZ variants run stable for years, no issues. I do not know how they fare with other motherboards, though.