Okay, you at one point said that your DIP was stuck. So I kinda went off that.

But if you are simply missing the pull up then all you need do is add a pull up resistor.

You could discover this by measuring your bf pins to vcc3 with the two bf jumpers/dips off. And then again to gnd with them on.

Here is a small device designed to augment the motherboard’s capabilities on bf pins directly.

Re: Socket 5/7/SS7 (Multiplier Mini) Tweaker (Beta)

Though in your case for your needs simply adding a resistor is probably all that is needed. If indeed your DIP isn’t stuck.

In fact you could add it to the right spot on the top of a plastic pin grid array pentium and it would I believe correct the problem for both cpus.

Here is how you could mod your cpu. Except that this is how a tillamook is modded, you would need to use different pins for yours.

Shown is a resistor between vcc3 and AMD/Cyrix/IBM/ST bf2
and a 0-ohm bridge between intel bf2 and AMD/Cyrix/IBM/ST bf2

What it sounds like you need is a resistor between vcc3 and bf1 or/and bf0 (two resistors if both)

Bf0 and bf1 should be these pins

After chatting with Mamba on discord we confirmed the details of the problem.

As suspected Mamba’s motherboard is missing a pull up. But not only that, it is missing two.

One is probably all that is needed to set 1.5/3.5x but both could be fitted if wanted.

Currently there are two 9-ohm pull downs and no pull ups on bf0, bf1

Intel specs pull ups at less than 2.1k I personally have seem motherboards using as low as 330 ohm pull ups.

This basically makes a voltage divider when the dip is closed. This is fine, as this is simply how it is done.

We didn’t check but I assume there are no provisions for bf2 intel or amd locations.

I confirm, thanks Sphere for your time.
Although I understood 20% of what I was doing, but I assume I did it properly.
Will follow your suggestion and let you know when my friend will have time to solder the resistors.

Mamba wrote on 2023-03-12, 21:21:

I confirm, thanks Sphere for your time.
Although I understood 20% of what I was doing, but I assume I did it properly.
Will follow your suggestion and let you know when my friend will have time to solder the resistors.

Be careful 😀

Before it disappears or I forgot, here a link with extensive modifications on both rev3b and 2A.
The guy even put pins on unpopulated jumpers for dual voltage.
But it was my understanding that was unnecessary… Was it???

http://dualsocketworld.blog134.fc2.com/blog-entry-285.html

Those pci mods they did are horrifying.
I saw someone do something similar on freeway motherboards.

If you need 3.3v pci, there are better ways.

Adding 3.3v to pci adapter(Released)

Sphere478 wrote on 2023-03-14, 03:17:

Those pci mods they did are horrifying. I saw someone do something similar on freeway motherboards. […]
Show full quote

Those pci mods they did are horrifying.
I saw someone do something similar on freeway motherboards.

If you need 3.3v pci, there are better ways.

Adding 3.3v to pci adapter(Released)

Not me,
Just shocked about the fact that the board really does not deliver 2.8v without modding it.
Is it for real?

Mamba wrote on 2023-03-14, 05:54:

Not me, Just shocked about the fact that the board really do not deliver 2.8v without modding it. Is it for real? […]
Show full quote

Sphere478 wrote on 2023-03-14, 03:17:

Those pci mods they did are horrifying. I saw someone do something similar on freeway motherboards. […]
Show full quote

Those pci mods they did are horrifying.
I saw someone do something similar on freeway motherboards.

If you need 3.3v pci, there are better ways.

Adding 3.3v to pci adapter(Released)

Not me,
Just shocked about the fact that the board really do not deliver 2.8v without modding it.
Is it for real?

Many socket 7 motherboards were like that.

It was common for boards to be released with missing or entirely not present core voltage plane circuitry.

Btw, if yours is missing this, you should use 2x pentium 200 p54c for your build.

Or
-interposers with 233s,
-mod the board to run 2.8v mmx 233s,
-use one 200 overdrive in primary socket, and a 233mmx in a interposer in the second socket at 233 (asymetric).

Those are your fastest dual cpu options.

Sphere478 wrote on 2023-03-14, 06:06:

Many socket 7 motherboards were like that. […]
Show full quote

Mamba wrote on 2023-03-14, 05:54:

Not me, Just shocked about the fact that the board really do not deliver 2.8v without modding it. Is it for real? […]
Show full quote

Sphere478 wrote on 2023-03-14, 03:17:

Those pci mods they did are horrifying. I saw someone do something similar on freeway motherboards. […]
Show full quote

Those pci mods they did are horrifying.
I saw someone do something similar on freeway motherboards.

If you need 3.3v pci, there are better ways.

Adding 3.3v to pci adapter(Released)

Not me,
Just shocked about the fact that the board really do not deliver 2.8v without modding it.
Is it for real?

Many socket 7 motherboards were like that.

It was common for boards to be released with missing or entirely not present core voltage plane circuitry.

Btw, if yours is missing this, you should use 2x pentium 200 p54c for your build.

Or
-interposers with 233s,
-mod the board to run 2.8v mmx 233s,
-use one 200 overdrive in primary socket, and a 233mmx in a interposer in the second socket at 233 (asymetric).

Those are your fastest dual cpu options.

The shocking part is not that it seems not to deliver actually, but that Gigabyte states the opposite since p55c IS present on compatibility table.
https://www.gigabyte.com/microsite/121/tech_mmxtable.htm

This is incredible

Anyway my two 166 mmx work fine (and so my 233mmx even if at 166 waiting to mod them), I have to take into consideration that they are litterally frying???

All GA-586DX with the two golden heatsinks at the CPU sockets DO suppurt dual voltage. I haven´s seen one without so far. There´s only one (non-5V) core voltage available - 2.8 / 2.9V for Pentium MMX (or single AMD CPUs).
There´s also a seperate 3.3V regulator for I/O etc.

Due to severe(!) BIOS limitations many "modern" PCI cards don´t work properly on the DX2.
Please also note that the GA-586DX is quite finicky in general. You will notice that when you install any OS like NT, 2K or Linux. As soon as you have SCSI, Video, Sound, Network (let alone USB) the IRQ hell will start.

majestyk wrote on 2023-03-14, 07:25:

All GA-586DX with the two golden heatsinks at the CPU sockets DO suppurt dual voltage. I haven´s seen one without so far.

Due to BIOS limitations many "modern" PCI cards don´t work properly on the DX2.
Please also note that the GA-586DX is quite finicky in general. You will notice that when you install any OS like NT, 2K or Linux. As soon as you have SCSI, Video, Sound, Network (let alone USB) the IRQ hell will start.

Mine is 2A, black heatsink.
I had a gold one years ago (see K6Plus forum), and with win2k I had zero issues, using a rage128AIW.
The only problem was usb. I had hard time finding a proper card, but was before I realise that NEC chipset was the way to go.
This one (Black 2A) has headers, but no usb options in bios.
I think the bios itself is crippled and needs modifications.

Don´t get me wrong, it´s not about the colour of the heatsinks but about the fact that they are present!
Why not post a picture of your board??

majestyk wrote on 2023-03-14, 07:25:

All GA-586DX with the two golden heatsinks at the CPU sockets DO suppurt dual voltage. I haven´s seen one without so far. There´ […]
Show full quote

All GA-586DX with the two golden heatsinks at the CPU sockets DO suppurt dual voltage. I haven´s seen one without so far. There´s only one (non-5V) core voltage available - 2.8 / 2.9V for Pentium MMX (or single AMD CPUs).
There´s also a seperate 3.3V regulator for I/O etc.

Due to severe(!) BIOS limitations many "modern" PCI cards don´t work properly on the DX2.
Please also note that the GA-586DX is quite finicky in general. You will notice that when you install any OS like NT, 2K or Linux. As soon as you have SCSI, Video, Sound, Network (let alone USB) the IRQ hell will start.

And this was the outcome (again, bios is crippled, wish I know how to fix it):

Your computer's system firmware does not include enough information to properly configure and use this device. To use this device, contact your computer manufacturer to obtain firmware or Bios update. (Code 35)

This error message is displayed when a device does not have an entry in the BIOS MultiProcessor Specification (MPS) table. You can only see this error message on MPS-capable systems. This behavior usually indicates a BIOS bug. This is particularly prevalent on MPS systems with multiple root PCI buses.

• Obtain a firmware or BIOS update. If no update is available, you cannot use the device.
• If the BIOS has an option to switch between MPS 1.1 and MPS 1.4, you can try switching because a different table is loaded. You usually want the system set to MPS 1.4.

Problem is that I can't switch from one MPS to another in the bios anyway.
The only settng I can change is "MPS 1.4 for single CPU = Disable/Enable".

Here

It´s dual voltage and it auto-detects the presence of dual voltage CPUs and sets Vcore accordingly. All is perfect here. Just fix the x3.5 multiplyer issue with a pull-up resistor at the BF0 pins, insert 2 x MMX233 and RAM as you like and it´s maxed out.

Mamba, Core voltage can be measured at vcc2 to vss. The easiest way to find this is center corner notch cpu pin -to- mobo mounting screw.

You are looking for 2.8vdc as your meter is not auto ranging. Set the range low like 10v or whatever option you have that is first above 2.8v

In any case, the replies above seem to have put the mystery to rest. Also, if it says it supports mmx, then it should support 2.8v vcc2

I’m saddened to hear about the issues with this board regarding irqs and whatnot. I have been wanting to get one of these for my collection.

I am quite curious if Mamba is going to be able to get 3.5x75 or 83 working. Has anyone else gotten that to work?

Sphere478 wrote on 2023-03-14, 08:15:

Mamba, Core voltage can be measured at vcc2 to vss. The easiest way to find this is center corner notch cpu pin -to- mobo mounti […]
Show full quote

Mamba, Core voltage can be measured at vcc2 to vss. The easiest way to find this is center corner notch cpu pin -to- mobo mounting screw.

You are looking for 2.8vdc as your meter is not auto ranging. Set the range low like 10v or whatever option you have that is first above 2.8v

In any case, the replies above seem to have put the mystery to rest. Also, if it says it supports mmx, then it should support 2.8v vcc2

I’m saddened to hear about the issues with this board regarding irqs and whatnot. I have been wanting to get one of these for my collection.

I am quite curious if Mamba is going to be able to get 3.5x75 or 83 working. Has anyone else gotten that to work?

I can be stubborn equally to my ignorance, that is limitless.
Will find someone with good bios modding capabilities and goodwill to fix the bios for IRQ table and anything 430HX related.

Mamba wrote on 2023-03-14, 08:26:

Sphere478 wrote on 2023-03-14, 08:15:

Mamba, Core voltage can be measured at vcc2 to vss. The easiest way to find this is center corner notch cpu pin -to- mobo mounti […]
Show full quote

Mamba, Core voltage can be measured at vcc2 to vss. The easiest way to find this is center corner notch cpu pin -to- mobo mounting screw.

You are looking for 2.8vdc as your meter is not auto ranging. Set the range low like 10v or whatever option you have that is first above 2.8v

In any case, the replies above seem to have put the mystery to rest. Also, if it says it supports mmx, then it should support 2.8v vcc2

I’m saddened to hear about the issues with this board regarding irqs and whatnot. I have been wanting to get one of these for my collection.

I am quite curious if Mamba is going to be able to get 3.5x75 or 83 working. Has anyone else gotten that to work?

I can be stubborn equally to my ignorance, that is limitless.
Will find someone with good bios modding capabilities and goodwill to fix the bios for IRQ table and anything 430HX related.

Re: Diy modding support for k6+And 120gb hard drives into bios roms

BIOS image collection - requests, discussion etc

How about a MR-BIOS ROM file repository?

Some reading