CalamityLime wrote on 2022-06-04, 01:21:

Yeah, voltage meters in chips can be spooky. […]
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Yeah, voltage meters in chips can be spooky.

Well thanks for checking what you checked.
Still, we'll see what comes of things whenever I get the PCBs . Though i still don't know if the motherboard works.
Yet to pick up a cpu for it.

I don't have a bíos code reader card so and i don't think they can beep without a cpu

What are your plans for it?

So many options on what you could get for it

Pentium Tillamooks are fun (you can overclock them to like 400mhz

The cyrix mII 300gp 2.0v is also a good overclocker being as it seems to have the same core as the 433gp.

K6-3+ is a obvious performance leader. 570 2+ can be modded into one. And are cheap.

Rise cpus are pretty fun. The iDragon is supposed to be a 2.0v version good for about 250mhz or so the hardware easter egg is cool

Winchip 2 would be a fun build. Apparently they had multipliers up to 5x?

Sphere478 wrote on 2022-06-04, 01:30:

What are your plans for it? […]
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What are your plans for it?

So many options on what you could get for it

Pentium Tillamooks are fun (you can overclock them to like 400mhz

The cyrix mII 300gp 2.0v is also a good overclocker being as it seems to have the same core as the 433gp.

K6-3+ is a obvious performance leader. 570 2+ can be modded into one. And are cheap.

Rise cpus are pretty fun. The iDragon is supposed to be a 2.0v version good for about 250mhz or so the hardware easter egg is cool

Winchip 2 would be a fun build. Apparently they had multipliers up to 5x?

I don't exactly have any plans for it, however the manual for the board suggests that the VRM goes down to 2.5v
If true, that limits things. What I do want is a basic pentium for just testing it.

Issue is always postage. Being in Ireland I'm always stuck paying for more expensive postage, very few sellers in Ireland will stuff I want to buy so I have to pay to bring items in from overseas.
I think I'm just going to try to nab whatever pops up for cheap.

With the usb-2-232-KBD circuit checked and a few things in code checked, plus the boards ordered, I have more free time for hobbies.
There are things about the KBD that I didn't mention yet and I wanted to avoid putting myself in a corner for how to implement things.
So I may look into the VRM of the Soyo to see if I can modify it to get her down to 2.2 or 2.0v

-lime

You know what, the VRM circuit is simpler than it looked.

First off, the VRM circuit is mirrored, one for the 3.3-ish io and another for the vcore.
For single voltage cpus, the whole thing is fed off of the first VRM with the second one sitting idle. Which is set with jumpers between the green and blue marked pins.

For Multivoltage, the second VRM is fed off of the first (with a set jumper on the back to switch between vrm 1 and 5v), jumpers between purple and blue. (so the small blue jumpers are the vcore voltage pins.
The big heatsinks are for PNP transistors that might benefit from a change. Let me know what ye think but I for one has a bad feeling about them.

The area marked in the larger purple is the regulator. The output voltage is configured the same as a LM317 with two resistors between vout and adj, so I can just bridge R151 and make my own jumper with a set resistor to replace it to change the voltage to what I want, the regulator spec sheet says that it can go down to 1.24.
On the topic of the spec sheet, it says that the 2951 regulator can do a max of 220ma, so I'm guessing that it's putting the pnp in line with that resulting in the pnp doing most of the work.
OR
Leave the second VRM idle and replace it with another one that steps 5v down to 2-odd v
5V is right there and the voltage pins are available.

What do ye think?

I know necroware made his mmx voltage regular thing for older socket 7's and that would be a good reference point.

Check out the vrm round up thread for ideas

Re: vrm module project thread roundup, share ideas, make new designs

Are there two regulator controllers? Are they both 2591?

Sphere478 wrote on 2022-06-04, 05:22:

Are there two regulator controllers? Are they both 2591?

Yes. Both the same.

CalamityLime wrote on 2022-06-04, 09:30:

Sphere478 wrote on 2022-06-04, 05:22:

Are there two regulator controllers? Are they both 2591?

Yes. Both the same.

what’s the full model number for that regulator? I’m trying to find the datsheet

Sphere478 wrote on 2022-06-04, 09:43:

what’s the full model number for that regulator? I’m trying to find the datsheet

Written on the chip it says
69jt
2951
CMB

I forgot which brand uses the infinity symbol on their parts.

Edit: national semi
http://chronolite2.narod.ru/sheets/LP2950.pdf

Trying to decipher this.

Many socket 7 controllers follow a base voltage of 2v or 2.1v and have four pins +0.1v, +0.2v, +0.4v, and +0.8v.

I’m not seeing that pattern here.

Lemme see if I can track down a datasheet on that regulator

Ah I see you found it. Edit, wait, that has a different model number..

Okay, I must be thinking pwm controllers, these linear regulators I guess you program them via resistor? And not with binary registers?

I think the answers you seek are in the correct data sheet.

I suspect, that replacing a smd resistor with a pot may be the way to do this.

Sphere478 wrote on 2022-06-04, 10:01:

Ah I see you found it. Edit, wait, that has a different model number.. […]
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Ah I see you found it. Edit, wait, that has a different model number..

Okay, I must be thinking pwm controllers, these linear regulators I guess you program them via resistor? And not with binary registers?

I think the answers you seek are in the correct data sheet.

I suspect, that replacing a smd resistor with a pot may be the way to do this.

Eh, model number is close enough 😂

Yeah a pot or a fixed resistor with the correct value.

But is that really fun enough? I'm curious if i can even feed the second vrm from a switching DC/DC just to cut down the temps of the vrms as a whole.

There is a jumper i didn't picture and i can tap into that to take 5v, step that down down to say 3ish and use the existing linear system to step that down to core voltage.

I'd have to feel the temps of it running before deciding if that's worthwhile or not.

I have a theory,

I think those three voltage jumper positions have one side tied together yes?

If so, next assumption is this,

The other side all goes to the same place but not before passing through a resistor that is different for each location?

If yes then,

Find the resistors,

Are the higher voltage settings higher or lower resistance?

If higher resistance gives lower voltage, then do this,

Grab a hdd led wire and solder a pot to it, plug it into it in to one of the jumper spaces and test the voltage at different settings.

You now have a way to set lower voltages. If My theory is correct. And no need to modify the board.

Hopefully I’m correct

Edit, sorry, I’ve been busy with stuff today, I see you already had this thought above. Lol

Check out that vrm round up thread for ideas if you wanna re invent the wheel here with the voltage 😀

Btw you can fire this board up and check voltage without a cpu.

It’s the middle pin on the corner with the notch. Use a resistor leg in the socket, with lever closed. (Open it to put it in, then close obv)

That pin, measure to ground.

Sphere478 wrote on 2022-06-04, 10:31:

Check out that vrm round up thread for ideas if you wanna re invent the wheel here with the voltage :-) […]
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Check out that vrm round up thread for ideas if you wanna re invent the wheel here with the voltage 😀

Btw you can fire this board up and check voltage without a cpu.

It’s the middle pin on the corner with the notch. Use a resistor leg in the socket, with lever closed. (Open it to put it in, then close obv)

That pin, measure to ground.

I've thought about that and I really should but I'm always spooked by the idea.
No so much powering the board without a CPU but powering the board as a whole.

Don’t understand.

If you´re using an ATX PSU with AT adaptor you can also add a wire from the 3.3V line of the PSU, connect it directly to the output of the I/O regulator (so it´s not used anymore) and to the input of the Vcore regulator. The voltage drop - and correlated heat dissipation - for let´s say a Pentium MMX 233 drops from 5V- 2.8V = 2.2V to 3.3V-2.8 = 0.5V. This would make the system far more energy efficient and reduce heat dramatically. It´s also a very cheap solution and can be reverted anytime.

Sphere478 wrote on 2022-06-04, 15:48:

Don’t understand.

as a wise man once said
"don't turn it on because if I don't test if the board works, it might"

majestyk wrote on 2022-06-04, 16:44:

If you´re using an ATX PSU with AT adaptor you can also add a wire from the 3.3V line of the PSU, connect it directly to the output of the I/O regulator (so it´s not used anymore) and to the input of the Vcore regulator. The voltage drop - and correlated heat dissipation - for let´s say a Pentium MMX 233 drops from 5V- 2.8V = 2.2V to 3.3V-2.8 = 0.5V. This would make the system far more energy efficient and reduce heat dramatically. It´s also a very cheap solution and can be reverted anytime.

Yeah, I thought about that too. I am using an ATX to AT device that I sort of made.

an old AT power supply exploded and thanks to crypto miners; atx break out boards are really easy to get. Feels a bit like cheating though but eh, could still be fun.

EDIT:
I also added a-5v circuit to it at some point. 12v -> 7805 -> chargepump
Because I had spare charge pumps and I wanted to keep as much load on the 12v rail as possible.

I’ve been thinking about adding a 3.3v rail to the pico psu adapter, if that holds any interest to anyone.

Re: ATX to AT pico Adapter!

3.3 from the pico at could be handy. You'd want a nice stable connector

Some simple feedback:

Pads:
Make the pads for the ATX connector larger (and the AT connector if there's space). The pads you have are on the smaller side, I think you'll find that solder will ball up on the conductor itself without a good contact to the pad. I've had issues with tiny pads doing this on even leaded solder.

Traces
I do see that you have nice thick traces for the -12 and -5 volt rails but to make room for the pads here are some numbers that might help:
You have the thick traces at around 50mil (1.25mm) which is good for around 1.4amps but most negative rails are about half an amp to an amp.
You're not going to see a whole amp on either the -12 or -5 but to accommodate an amp you want around 32mil which is about 0.8mm.

For PWR_OK
It's a signal line so you don't need much. To accommodate say half an amp (can't find a proper spec but it feels right) you want a trace about 0.35mm

I'm giving trace thickness measurements based on 1oz copper, if you're using 2oz copper than you can half the thickness.

Hope that helps a bit.

I had to find some of information on trace thickness for the USB-2-232-KBD to deal with RGB keyboards. Ultimately it came down to fitting the thickest trace I could fit.