JamesF36 wrote on 2022-06-12, 02:51:

You guys misunderstood the premise of this build! It’s supposed to be an experiment how far I can push a socket 5 system. My super period correct systems are my upcoming socket 7 build and the socket 370 pentium 3 build. I got the SB live out of my socket 462 athlon build since that motherboard has built in sound and is just simply an XP machine (don’t need special sound card for that build)

Nobody really tried to stick a K6-233ANR in a socket 5? Cmon guys I’ve read that at least one person has done it!!

I'm not sure who you're referring to, but I'm at least one of those who did that. Much more so, because I used a full blown K6-2.
The trick up my sleeve was a VRM header on said board, which allowed me to use any CPUs with dual power planes I wanted. You will have a limited experience with just a single 3.3V rail.

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

JamesF36 wrote on 2022-06-22, 18:45:

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

We need to know what signals your motherboard is sending to know what the cpu needs.

The multipliers under 3x are probably scrambled. What gives 2x on one of these chips may give 2.5x on another

Do the guide and post results.

Or order and build a tweaker.

Here are the typical settings though.

JamesF36 wrote on 2022-06-22, 18:45:

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally have.
This effectively limits the max bus ratio which you can achieve without modifications. To fix it, you will have to manually pull up BF0 to 5V with a resistor (at least a few hundred ohms).

computerguy08 wrote on 2022-06-23, 15:03:

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally hav […]
Show full quote

JamesF36 wrote on 2022-06-22, 18:45:

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally have.
This effectively limits the max bus ratio which you can achieve without modifications. To fix it, you will have to manually pull up BF0 to 5V with a resistor (at least a few hundred ohms).
multi pin.png
multi pin MMX.png

yep 😀

Intel specs the pull up at 2.2k or less but I’ve seen as low as 330 ohms used for pull up.

It seems that generally, you want your pull down to be 1/4 to 1/13th of the pull up rating (these numbers based on actual observations in field of what has been used)

computerguy08 wrote on 2022-06-23, 15:03:

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally hav […]
Show full quote

JamesF36 wrote on 2022-06-22, 18:45:

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally have.
This effectively limits the max bus ratio which you can achieve without modifications. To fix it, you will have to manually pull up BF0 to 5V with a resistor (at least a few hundred ohms).
multi pin.png
multi pin MMX.png

Sounds simple enough right? I just gotta solder a resistor to the BF0 pin on the back of the motherboard? Where would I have to solder the other end of the resistor to (sorry for my confusion)

JamesF36 wrote on 2022-06-24, 23:58:

computerguy08 wrote on 2022-06-23, 15:03:

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally hav […]
Show full quote

JamesF36 wrote on 2022-06-22, 18:45:

After fiddling around for many hours with this motherboard I think i’ve come to the conclusion this motherboard only goes up to 2x multiplier as it is … if I want 3x i’m gonna have to do some modification, but i’ve seen people modify their CPU to do the proper multiplier.. how is that done?

This is because you are using an MMX chip on a socket 5 board, which lacks the pull-up on BF0 that classic Pentiums normally have.
This effectively limits the max bus ratio which you can achieve without modifications. To fix it, you will have to manually pull up BF0 to 5V with a resistor (at least a few hundred ohms).
multi pin.png
multi pin MMX.png

Sounds simple enough right? I just gotta solder a resistor to the BF0 pin on the back of the motherboard? Where would I have to solder the other end of the resistor to (sorry for my confusion)

On the previous page I posted a guide. Please do that and report results. Or just order a multiplier mini tweaker, populate it and start playing with the bf0, bf1 switches.

JamesF36 wrote on 2022-06-24, 23:58:

Sounds simple enough right? I just gotta solder a resistor to the BF0 pin on the back of the motherboard? Where would I have to solder the other end of the resistor to (sorry for my confusion)

Just find any pin on the motherboard which supplies 5V. If not sure, you can grab 5V from the Keylock connector. The lonely pin at the end is the one which has 5V most times, use a multimeter to verify.
EDIT: the multiplier pins need 3.3V for pull-up (as Sphere pointed out), which you can grab from the CPU power rail

computerguy08 wrote on 2022-06-25, 15:36:

JamesF36 wrote on 2022-06-24, 23:58:

Sounds simple enough right? I just gotta solder a resistor to the BF0 pin on the back of the motherboard? Where would I have to solder the other end of the resistor to (sorry for my confusion)

Just find any pin on the motherboard which supplies 5V. If not sure, you can grab 5V from the Keylock connector. The lonely pin at the end is the one which has 5V most times, use a multimeter to verify.

If you want it to be more compact, have a look at the socket 5/7 pinout, I recall it having 1 or 2 pins with 5V supply.

The pullups on the bf Are designed to be pulled to vcc3 not vcc5. 5v may fry the processor.

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

Here is a simplified multiplier circuit.

Depending on how your pull ups and down resistors are configured you may have to use lower values. But the pull up is to vcc3 and the pull down is to vss.

Sphere478 wrote on 2022-06-25, 20:19:

The pullups on the bf Are designed to be pulled to vcc3 not vcc5. 5v may fry the processor.

Ah yes, you are right, I forgot that aspect. Supposed to be 3.3V not 5.

computerguy08 wrote on 2022-06-25, 23:12:

Sphere478 wrote on 2022-06-25, 20:19:

The pullups on the bf Are designed to be pulled to vcc3 not vcc5. 5v may fry the processor.

Ah yes, you are right, I forgot that aspect. Supposed to be 3.3V not 5.

It would probably work on vcc2 depending on the voltage. But there is no point to try it, as the specified voltage is present right there at the pins.

Given that it has an internal pull-down, it may not necessarily end up as 5V after the initial resistor mod (resistor ladder gets made), but it's better to play it safe.

You can tell I'm very used to working with 5V TTL circuits 🤣

computerguy08 wrote on 2022-06-25, 23:16:

Given that it has an internal pull-down, it may not necessarily end up as 5V after the initial resistor mod (resistor ladder gets made), but it's better to play it safe.

You can tell I'm very used to working with 5V TTL circuits 🤣

Not all processors have internal pull downs. This is a misconception.

But yes, you may be right. Resistor networks depending on values may result in correct voltage or current. But also agree, play it safe. That’s why I list maximum values on tweaker (which are often too small to read 🤣)

You can tell I'm very used to working with 5V TTL circuits 🤣

Indeed haha.

Sphere478 wrote on 2022-06-25, 23:19:

Not all processors have internal pull downs. This is a misconception.

I thought we were talking just MMX usage on a Socket 5 board. For others it will be different obviously.

computerguy08 wrote on 2022-06-25, 23:22:

Sphere478 wrote on 2022-06-25, 23:19:

Not all processors have internal pull downs. This is a misconception.

I thought we were talking just MMX usage on a Socket 5 board. For others it will be different obviously.

I’m pretty sure that Mmx is one of the ones missing a pull up. Above in a previous reply you said it was.

In any case, to test it:
Put a ohm meter between vcc3 and BF(x) to find out.

Sphere478 wrote on 2022-06-25, 23:30:

computerguy08 wrote on 2022-06-25, 23:22:

Sphere478 wrote on 2022-06-25, 23:19:

Not all processors have internal pull downs. This is a misconception.

I thought we were talking just MMX usage on a Socket 5 board. For others it will be different obviously.

I’m pretty sure that Mmx is one of the ones missing a pull up. Above in a previous reply you said it was.

Yes, I even said so, with screenshots from the datasheet. Besides the little voltage mishap, I don't think I got any other details wrong. I'm taking specifically about BF0 on the MMX, which has a pull-down internally and which can be fixed on Socket 5 boards with a pull-up resistor to 3.3V. Hopefully I made myself clear enough.

And I'm not the only one to have done this mod, Necroware did a video on MMX + Socket 5 as well, with the same multi pin mod I'm suggesting (around 8:00 in the video).
https://www.youtube.com/watch?v=J0NLGfocviU

computerguy08 wrote on 2022-06-26, 09:38:

Yes, I even said so, with screenshots from the datasheet. Besides the little voltage mishap, I don't think I got any other detai […]
Show full quote

Sphere478 wrote on 2022-06-25, 23:30:

computerguy08 wrote on 2022-06-25, 23:22:

I thought we were talking just MMX usage on a Socket 5 board. For others it will be different obviously.

I’m pretty sure that Mmx is one of the ones missing a pull up. Above in a previous reply you said it was.

Yes, I even said so, with screenshots from the datasheet. Besides the little voltage mishap, I don't think I got any other details wrong. I'm taking specifically about BF0 on the MMX, which has a pull-down internally and which can be fixed on Socket 5 boards with a pull-up resistor to 3.3V. Hopefully I made myself clear enough.

And I'm not the only one to have done this mod, Necroware did a video on MMX + Socket 5 as well, with the same multi pin mod I'm suggesting (around 8:00 in the video).
https://www.youtube.com/watch?v=J0NLGfocviU

Progress! Extremely close but still not quite there yet for me - I managed to solder a 1k ohm resistor between BF0 and the 3.3v and boom - it now reads as 166mhz! (whereas before it'd read as 133mhz) and it seems this is the highest I can get it with the resistor (strange) other speeds came up as 120mhz and 150mhz.. I wonder what's missing here still to not be at 200mhz? Did I use too high Ohms? I have 220 ohm resistors on hand if need be (i'm assuming it's currently running at 2.5x.. so close to 3x.. so close) definitely an improvement of the original 2x max but I really want it to be at 3x

You could follow the guide I posted.

Maybe that way you would know what you are dealing with rather than throwing darts in the dark.

Typically a 1k is usually sufficient for a pull up. The fact that it changed suggests that it worked. (On that bf)

I should also remind those reading that running a mmx at 3.3v is pretty risky to your hardware. OP has exclaimed that they don’t care if I recall though I believe in OP.

Sphere478 wrote on 2022-06-26, 23:42:

You could follow the guide I posted. […]
Show full quote

You could follow the guide I posted.

Maybe that way you would know what you are dealing with rather than throwing darts in the dark.

Typically a 1k is usually sufficient for a pull up. The fact that it changed suggests that it worked. (On that bf)

I should also remind those reading that running a mmx at 3.3v is pretty risky to your hardware. OP has exclaimed that they don’t care if I recall though I believe in OP.

My bad! I knew I was supposed to do something,

resistance between vcc3 and bf0 is 1k ohms (as expected)
resistance between vcc3 and bf1 is reading at 0

bf0+vss:
1.588 resistance between bf0 and vss with 0 jumpers..
1.553 when pins 7,8 jumped
1.548 when 5,6 jumped
1.586 when 3,4 jumped
1.586 when 1,2 jumped
(strange how it changes with 7,8 and 5,6? shouldn't a bf0 jumper just be 1 set not 2?)

bf1+vss
0 resistance between bf1 and vss with no jumpers
0 with pins 7,8 jumped
0 with pins 5,6 jumped
0 with pins 3,4 jumped
0 with pins 1,2 jumped

what on earth? this board is such a mystery to me!

edit: resistance changed when i jump pins 1,4 for bf1+vss... strange huh

oem boards are so weird

i've seen somewhere that I can modify bf1 and wire it to somewhere but i forgot where...

Can you clarify your readings? 0 means short. Did you mean to say that or do you mean open?

Also 1.553 what? 1.553 ohms? K ohms, m ohms?

Without knowing the range of the readings it doesn’t tell anything.

If I make some assumptions about what I think you “meant” it sounds like you may be missing both pull ups and not have a jumper at all for bf1.

But I can’t really make that assumption without clarification on your readings.

You could just order a tweaker and some smd resistors/switch. If your soldering skills are up to it.

You will then have switches for all of this and figuring it out will be easy.