Hi,

All AMD K6 models that are rated for speeds above 233 MHz, support all 8 possible Multiplier combination of the three BF0/BF1/BF2 jumpers.
So above the standard x2. 0; x2. 5; x3.0; x3. 5 settings, x4.0; x4.5; x5.0; x5.5 Multiplier settings are possible as well.

For your TX97-X Rev 3, the undocumented settings are:
X5.0 - BF0: 1-2; BF1: 2-3; BF2: 2-3
X5.5 - BF0: 1-2; BF1: 1-2; BF2: 2-3

Note that the K6-2CXT, K6-III, K6-2+, and K6-III+ models have a x6.0 Multiplier as well. Just set the board for x2 and you will get x6 on these CPU's.
This nice feature will allow speeds up to 400 (6x66) and 450MHz (6x75) on this board! 😊

I know there are also more Vcore settings possible on this board. I will look them up when I'm back home this Saturday.

Cheers, Jan

Excellent! Thanks!

Chkcpu wrote on 2024-09-09, 16:07:

Hi, […]
Show full quote

Hi,

All AMD K6 models that are rated for speeds above 233 MHz, support all 8 possible Multiplier combination of the three BF0/BF1/BF2 jumpers.
So above the standard x2. 0; x2. 5; x3.0; x3. 5 settings, x4.0; x4.5; x5.0; x5.5 Multiplier settings are possible as well.

For your TX97-X Rev 3, the undocumented settings are:
X5.0 - BF0: 1-2; BF1: 2-3; BF2: 2-3
X5.5 - BF0: 1-2; BF1: 1-2; BF2: 2-3

Note that the K6-2CXT, K6-III, K6-2+, and K6-III+ models have a x6.0 Multiplier as well. Just set the board for x2 and you will get x6 on these CPU's.
This nice feature will allow speeds up to 400 (6x66) and 450MHz (6x75) on this board! 😊

I know there are also more Vcore settings possible on this board. I will look them up when I'm back home this Saturday.

Cheers, Jan

I got the K6-2 333 working with your help, then I went down the rabbit hole of finding out about K6+ chips and the on-the-fly tweaking you can do. Got the patched BIOS installed for + support and a K6-2+ 550ACZ on the way. It's rated for 100MHz FSB and 5.5x multiplier, I'll have to run it at 66 or 75, but will it go to 6x like you were describing if I set that on the board even though it's only rated for 5.5x?

Also the new chip says it needs 2V, not 2.1V like the board setting. Is that a small enough difference to not matter?

Need to know the Vreg IC (pics of the TX97-XE v3 shows a HIP6008CB and uses same jumpers for same volts)....can you post a close up picture or tell us what the chip is ?
If same vreg controller then the V Out is controlled by internal resistors thru the jumpers. Datasheet says 2.0v is do-able but does not give ....
Note: You can use 2.1v as is within the AMD spec (2.0v +/- 0.1v) but I suspect might be a way to set it at 2.0v...maybe

x73rmin8r wrote on 2024-09-11, 22:32:

Chkcpu wrote on 2024-09-09, 16:07:

Hi, […]
Show full quote

Hi,

All AMD K6 models that are rated for speeds above 233 MHz, support all 8 possible Multiplier combination of the three BF0/BF1/BF2 jumpers.
So above the standard x2. 0; x2. 5; x3.0; x3. 5 settings, x4.0; x4.5; x5.0; x5.5 Multiplier settings are possible as well.

For your TX97-X Rev 3, the undocumented settings are:
X5.0 - BF0: 1-2; BF1: 2-3; BF2: 2-3
X5.5 - BF0: 1-2; BF1: 1-2; BF2: 2-3

Note that the K6-2CXT, K6-III, K6-2+, and K6-III+ models have a x6.0 Multiplier as well. Just set the board for x2 and you will get x6 on these CPU's.
This nice feature will allow speeds up to 400 (6x66) and 450MHz (6x75) on this board! 😊

I know there are also more Vcore settings possible on this board. I will look them up when I'm back home this Saturday.

Cheers, Jan

I got the K6-2 333 working with your help, then I went down the rabbit hole of finding out about K6+ chips and the on-the-fly tweaking you can do. Got the patched BIOS installed for + support and a K6-2+ 550ACZ on the way. It's rated for 100MHz FSB and 5.5x multiplier, I'll have to run it at 66 or 75, but will it go to 6x like you were describing if I set that on the board even though it's only rated for 5.5x?

Also the new chip says it needs 2V, not 2.1V like the board setting. Is that a small enough difference to not matter?

Okay, you got a K6-2+/550 coming. Nice!
The x6 Multiplier will definitely work on this CPU. At 450MHz (6x75) you are still running below it's rating so you won't be overclocking anything.

I just noticed that when you download the patched TX97-X 0112x-1 BIOS from TheRetroWeb, you get the patched 0112xe-1 BIOS for the TX97-XE instead! I will send them a message to correct this.
So I hope you downloaded the 0112x-1 patch J.3 BIOS from my "The Unofficial K6-2+/K6-III+ page". 😉 The link is in my signature below.

I fully agree with Horun that 2.1V is perfectly fine for these K6plus CPUs. But I believe a 2.0V is possible on this board and I hope to find it in my archive this weekend.

Jan

Thanks for the responses!

I'll get a picture of the chip tonight.

Also, chkcpu, I did actually get the bios from your page without realizing it was yours, thanks for hosting that. Feels like comfy old internet, where just some guy could have a back alley page with the exact thing you need on it that isn't anywhere else. I want to go back.

"Site created with Microsoft Notepad" and a Garfield cartoon are great touches.

Thanks about your feedback on my website.
I started this site over 25 years ago, so it actually is “old internet”. 😉

Okay, I’m back home and found my notes about the undocumented settings. They appear to be to same for both the TX97-X and TX97-XE boards.
A part of this information was published on the German Asus support pages and an archived copy can be viewed at:
http://web.archive.org/web/20010405021548/htt … p5cpu_supp3.htm

This is what I found for the TX97-X:

CPU External (Bus) Frequency:
Note that it depends on the clockchip used if the 83MHz setting actually works.
83MHz -> FS0: 2-3, FS1: 1-2, FS2: 1-2

CPU to BUS Frequency Ratio:
5.0x -> BF0: 1-2, BF1: 2-3, BF2: 2-3
5.5x -> BF0: 1-2, BF1: 1-2, BF2: 2-3
6.0x -> BF0: 2-3, BF1: 1-2, BF2: 1-2
Note that the 6.0x setting only works on the K6-2CXT, K6-III, K6-2+, and
K6-III+ CPU. Other CPUs will do 2.0x with this setting. All K6-2/400 and
faster K6 CPUs have the CXT core.

CPU Vcore Voltage:
2.1V -> VID0: 1-2, VID1: open, VID2: open
2.2V -> VID0: open, VID1: 1-2, VID2: open
2.3V -> VID0: 1-2, VID1: 1-2, VID2: open
2.4V -> VID0: open, VID1: open, VID2: 1-2

I didn’t find a 2.0V setting, but as indicated before, you can safely use the 2.1V setting for 2.0V K6+ CPUs.
For all K6-2 CPUs, use the 2.2V setting (except the 2.4V K6-2/450AHX).
For boards with an extra VID3 jumper, there are even settings for 1.8V and 1.9V in the manual:
1.8V -> VID0: open, VID1: open, VID2: open, VID3: 1-2
1.9V -> VID0: open, VID1: open, VID2: open, VID3: 2-3
If your board has the VID3 jumper, you can try 1.9V Vcore with your K6-2+/550. Because you will be underclocking this CPU, the 1.9V setting will probably work fine.

Caution: On the TX97-X Rev 3.x and TX97-XE Rev 3.x boards, the VID0-2 decals on de board may be reversed. If so the settings will be:
2.1V -> VID0: open, VID1: open, VID2: 1-2, VID3: open
2.2V -> VID0: open, VID1: 1-2, VID2: open, VID3: open
2.3V -> VID0: open, VID1: 1-2, VID2: 1-2, VID3: open
2.4V -> VID0: 1-2, VID1: open, VID2: open, VID3: open
I don’t know if this is the case on your board, so be careful when setting Vcore.
With the K6-2/333 fitted, you can test this by selecting VID0: open, VID1: open, VID2: 1-2. If the decals are reversed, you will get 2.1V, otherwise you get 2.4V Vcore and you have to use VID0: 1-2, VID1: open, VID2: open for 2.1V.
You can check the Vcore voltage in the POWER MANAGEMENT SETUP menu in the BIOS, or with a multimeter.

About the 83MHZ FSB setting, it should be noted that a higher than 66MHz FSB exceeds the chipset and PCI specifications, because the 430TX chipset uses a fixed 2/1 divider between the FSB and PCI bus clock. Normally, the PCI runs at 66/2 = 33MHz. When running at 83MHz FSB, the PCI is automatically overclocked to 83/2 = 41,5MHz. This is a 25% increase above the norm. Busmaster cards, like SCSI-Controllers or networking cards are especially sensitive to frequencies over 33MHz. But 37.5MHz (FSB 75) is usually OK.
So a 450MHz (6x75) CPU speed should be reachable without stability problems.
If 83MHz is stable on your board, you can reach 500MHz (6x83).

Happy tinkering, Jan

Thanks a bunch for all the info!

I took a picture of that chip in case it's ever useful for anybody in the future.

I had a question about the voltage. From the manual for the 3.0 TX97-X board on the ASUS site it gives V0 1-2, V1 2-3, V2 open, V3 open for 2.1v. That's what I set for the k6-2 333 2.2V and it seems to work. It boots that way and I've played a decent amount of games with it set that way with no apparent issues. The bios shows 2v, with lots of errors in the other voltages that I'm not sure if I should be worrying about...

The info you gave me from the other more complete manual is V0 open, V1 open, V2 1-2, V3 open for 2.1v.

I don't think I understand this correctly, should I leave it how it is or have I got something wrong?

Edit: Looking closer, the original manual only lists regular k6's not k6-2's, so I probably just stumbled onto something that only accidently works, but the bios is showing 2v, and I didn't run into any errors playing anything. You think I could have damaged something this way?

Great to hear your K6-2/333 2.2V CPU runs well on 2.1V Vcore.

Looking at the picture of the Voltage Monitor in the BIOS, I believe the settings from the Asus TX97-X Rev 3.00 manual from August 1997 are indeed correct for your 3.0 board.
So the VID0: 1-2, VID1: open, VID2: open, VID3: open setting is correct for 2.1V Vcore. Note that, according the German Asus support site, the “open” setting for VID0-2 is the same as setting the jumper on pins 2-3.

Sorry about confusing the Vcore settings issue with a second voltage table for reversed VID0-2 settings. I have reports of boards that are wired this way, but this seems not to apply to your 3.0 board. So use the manual and the first Vcore table from my previous reply for the Vcore settings.

A nice check would be to set VID0: open, VID1: 1-2, VID2: open for 2.2V as documented on the German Asus page. This will run your K6-2/333 at its rated 2.2V.
Now check in the BIOS if the Voltage Monitor reading of 2.0V is increased to 2.1V or 2.2V. This BIOS Vcore Voltage reading can be a bit crude and a 0.1V deviation from the set voltage is nothing to worry about.
But with the 2.2V setting, you should see an increase from the previous 2.1V setting.

The other voltage readings in the Voltage Monitor are indeed way off.
I’ve seen this before when using faster CPUs like K6-2(+) on TX97- boards, and it’s probably caused by timing issues when the BIOS reads the monitoring chip. Just ignore these erroneous readings.

Greetings, Jan

Ah, the fact that 2-3 is actually open made it make sense! Thanks.

I changed the jumpers to 2.2V, and voltage measurement is still 2.0V, but maybe it's still not showing the 0.2V difference for the same reason all the other voltages look wrong.

Once I get the k6-2+ in I'll post back here and share how it turned out, and what FSB speeds I can get.

Thanks so much for the help.

Got the K6-2+ running! 6x at 75MHz at 2.1V. Didn't try 83MHz, figured the extra stress on the motherboard wouldn't be worth 50MHz.

Thanks for the help everybody.

NOTE TO ANYBODY ELSE TRYING THIS:

Make sure you apply the AMDK6UPD.EXE or similar patch to Windows 95 before putting in any CPU 350MHz or faster or it won't boot. Ask me how I know. Otherwise you'll have to set the jumpers to slow it down or put the old one back in to patch it, or just use Win 98 like rational people do.

Very nice that you got the TX97-X running with a K6-2+ at 450MHz now! 😀

However, I’m still worried a bit about the Vcore setting because of many reports about reversed VID0-2 settings on Rev 3.x TX97-X and TX97-XE boards.
Reading back in this thread, it troubles me that the Vcore indication in the BIOS stayed fixed at 2.0V when you set the jumpers for 2.2V. In hindsight, this makes this indication unreliable for determining if the VID0-2 settings on your rev 3.0 board at reversed or not.

For the K6-2/333 it didn’t matter, because the 2.2V VID0-2 setting stays the same when you reverse it. But for the K6-2+, the 2.1V setting will become 2.4V when you reverse it, and vise versa.
Do you have a multimeter to measure the Vcore, so you know for sure you don’t feed 2.4V to your nice K6-2+?
If not, and your board has the VID3 jumper, a safe alternative is to use the unambiguous 1.9V setting for your K6-2+ until you have the means to measure the Vcore.

Greetings, Jan

Perhaps many don't know it, but you can easily measure the VCore on the mosfet, I have highlighted in the figure the PINs where to find the VCORE, in practice the central pin corresponds to the upper part, since the central pin is tiny, and there are the others two very close together, just put the red probe in the upper part (see highlighting), and the black probe in any ground point, usually a black molex wire, set the tester to VDC, and find the right mosfet, among those of the VRM.
With this simple measurement, you can verify that the VCore voltage is the desired one, or if you measure a higher voltage, you could try to lower it, with a HW modification, if I'm not mistaken they usually use a resistor connected to ground.

Thanks for looking out Chkcpu, and thanks for the instructions on how to measure the voltage PC@live.

If I've done this right, I got these voltages measuring from the baseplate looking contact underneath the components to a black wire in a molex for ground:

Red dot: 2.16V
Yellow dot: 5.05V
Green: 3.65V
Blue: 5.08V

I assume the 2.16V one is the one that's supposed to be 2.1V, so it should be good to go, right?

If that's right I shouldn't need to worry about setting it to 1.9V, but just out of curiosity what happens if you run a cpu at slightly less voltage than it wants? Do you lose a little bit of speed, or is it an "it works or it doesn't" type thing?

As a sidenote and a suggestion, do also configure the advanced AMD features using CTU as I found you could do for an extra performance boost.

I have the -XE board variant with the same overclock as you, and I found (at least for games) write allocation and write combining had a bigger impact on performance than did the actual overclock. Not saying the overclock isn't worth it, but you have to squeeze every ounce of performance from these things, don't you. 😀

@x73rmin8r, thanks for putting my mind at ease. 😉
Your measurements make perfectly sense and the transistor with the red dot is clearly the one that regulates the Core voltage.

Your K6-2+ is indeed running happily at 2.1V Vcore. So no worries to need to run it at 1.9V.
A 1.9V Vcore is still within spec for this 2.0V CPU, and at 1.9V it will run with the same performance as on 2.0V or 2.1V. But it will depend on how hard it has to work if it remains completely stable. That’s why I always run a number of heavy benchmarks when I need to undervolt a CPU.
Just to give you an idea of what these K6plus CPUs are capable of, I have an Iwill XA100 board that can be set to 2.2V or 1.8V Vcore, but has no setting in between. I run a 2.0V K6-2+/450 at 500MHz on this board at 1.8V Vcore and it is completely stable!

@leonardo, thanks for your suggestion to further improve performance by using this nice win95/98 CTU tool.
Although the patched BIOSes for both the TX97-X and TX97-XE have full K6-2(+)/III(+) Write-Allocation support, Write-Combining is not supported.
I’ve never seen an Award socket 7 BIOS with Write-Combining support, only a few AMI BIOSes have that. So your performance increasing tip works well on most socket 7 boards when using a K6-2(+)/III(+). 😀

Cheers, Jan