SORRY I was confused.
My CPU is actually 266MMX and not 233.
Picture:

I haven't touched the jumpers.
I tried to use 133MHZ NON MMX without changing the jumpers and I got 110MHZ, but the problem was still the same.

The original 266MMX was running like that on 3.8Volt for all the time.

Stop what you are doing turn it off

Do not run that cpu anywhere near 2.8v

That is a 1.9v processor.

You also have to do some mods to it to make it work in your motherboard.

Re: Tillamook 266MHz and working L2 cache?

If you don’t have voltage settings under 2.1v-(2.2v max) then don’t use it.

It’s surprising that you got the cpu to 266mhz in your motherboard without modding it….

Ok, this CPU is rated for 1.9V. If it has been running at 3.38V for a long time it may have degraded.
The regular Pentium may have problems with the higher FSB. (Though that's not likely.)
Please reduce the core voltage of the MMX to 2.1V by moving the jumper from J8 to J15 and selecting 2.1V with J13 and see if your problems go away.

Sphere478 wrote on 2022-03-23, 10:05:

Do not run that cpu anywhere near 2.8v

I know this is going to hurt an S7 fan like you so brace yourself: The CPU was even running at 3.38V.🤐

Doornkaat wrote on 2022-03-23, 10:07:

Sphere478 wrote on 2022-03-23, 10:05:

Do not run that cpu anywhere near 2.8v

I know this is going to hurt an S7 fan like you so brace yourself: The CPU was even running at 3.38V.🤐

😱

^edits

This does bring up a interesting cooling option though,

Get that thing to 1.6v-1.9v and 133-233mhz and you probably won’t need a heatsink

Edit, has this been brought up, I think he has fsb set to 75mhz? Edit: yep I see in the pic set to 75.
That’s how he got it to 266 262 actually

I did a test on my tillamook.

133mhz at 2.15v

It gets warm enough that I have to keep it cool with my hand.

At 1.6-1.9v it may be possible but 2.1v is a bit too much voltage for no heatsink

Here is a pic of the tillamook mods I did to my 266 chips.

Sphere478 wrote on 2022-03-23, 10:19:

Okay, so your jumper below the cpu lever, move it to 2.1. […]
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Okay, so your jumper below the cpu lever, move it to 2.1.

Set your cpu multiplier to 2x or 2.5x (whichever shows lower frequency in bios)

And set your bus jumper to 50

And see if the chip gets hot (touch with finger)

I suspect it will just be warm.

Might solve your heatsink problems 🤣

Later when you get your cooling figured out we can get that chip going 75x4 😁

J8 and J15 select between P54C and P55C, so moving the jumper from J8 to J15 seems to select between single voltage and split voltage CPUs. Don't forget to do this as well, OP.

Thanks, I will try that today.
So P54C is for non MMX cpu, and P55C is for MMX cpu?

that's how I got the computer running with 3.38V, picture I supplied of the 266mhz is from the internet, I will take a picture of mine today also (but was there a different 1.9v and 3+v by standard?)

I have found a place here that is selling a used Totem TM-586 IV2 motherboard for cheap.
It's Intel 430VX chip instead of 430TX (128MB RAM support instead of 256MB but I'm using 64MB anyway).
Is it an ok swap if mine is defective after the tests?

Yes, P54C is the non-MMX Pentium, P55C is regular Pentium MMX.

All 266MHz Pentium MMX use the Tillamook core and require even lower voltages than the regular P55C Pentium MMX. No Pentium MMX is supposed to run at 3.xV. Regular P55C chips will endure this with sufficient cooling but I wouldn't do this to a Tillamook core.

The Totem TM-586 IV2 appears to support 2.9Vcore at the lowest setting so I would not get it for this CPU.

for those interested,

I decided to play with my 266mhz tillamook a little more (with a heatsink, see edits^)

sims 1 which was quite playable with the k6-3+ 400 is now quite laggy. a very significant performance drop from the k6-3+ 400mhz

system specs:
1x tillamook 266 w/mods
tyan s1464D
radeon 7000
256mb 2x128 simms 60ns
ide hdd
no sound card

this is a similar setup to what you could make with your hardware except, I can cache up to 512mb with this board when using a non k6-3/2+/3+ processor where as you can only install 128mb of ram and cache 64mb unless you install a k6-3?2+/3+ at which point you can run all 128mb without much performance hit.

so based on this you really want a k6-3/2+/3+ you'll really notice the improvement over a tillamook at 266

but that tillamook at 75x4 will be one hell of a upgrade over your old 133 p54c

2.9v is fine for a pentium MMX.
The 2.8v requirements for it have an official tolerance of +-0.1V.

Many people have run pentium MMX with higher voltage for years with a bigger heatsink. 2.9v won't hurt it in comparison. It's not even out of the spec

Sphere478 wrote on 2022-03-23, 11:42:

Thank you for your private message Sphere478, but I can't reply there yet since I'm new and don't have the option.

I hope the 266 is fine as it was never overheated, and the same problem occurred on my 133.
This problem did not happen before I replaced the 2 capacitors. but it worked fine for 1 hour after changing them.

I will look tonight when I get home if lower voltage works ok.

So I should be changing to 2.8V, put the jumper on J15 instead of J8.
Should I change the J7 jumper to something?

No prob, 😀

idan182 wrote on 2022-03-23, 14:05:

Thank you for your private message Sphere478, but I can't reply there yet since I'm new and don't have the option. […]
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Sphere478 wrote on 2022-03-23, 11:42:

Thank you for your private message Sphere478, but I can't reply there yet since I'm new and don't have the option.

I hope the 266 is fine as it was never overheated, and the same problem occurred on my 133.
This problem did not happen before I replaced the 2 capacitors. but it worked fine for 1 hour after changing them.

I will look tonight when I get home if lower voltage works ok.

So I should be changing to 2.8V, put the jumper on J15 instead of J8.
Should I change the J7 jumper to something?

If we are talking about the 266, use the 2.1v setting. (It appears to be your lowest setting)
Any yes, do select the dual plane option via jumpers (sometimes labeled p55c)

But you need to do the mods also so you can get 4x and l2 cache working.

Edit:

This setting here, set the jumpers for p55c when you use the tillamook 266, and set to p54c when you use the pentium 133.

This should be your dual/single plane voltage setting

P55c is dual plane.

Cpus between 120mhz and 266mhz were a grey area but below that and it’s single plane, above that, it’s dual plane.

Your 133 is a single plane, your 266 is a dual plane

If my J8 is ON, why am I seeing 110MHZ when I connect my 133 CPU?
something with the multiplier?

idan182 wrote on 2022-03-23, 14:42:

If my J8 is ON, why am I seeing 110MHZ when I connect my 133 CPU?
something with the multiplier?

J8 has most likely nothing to do with multiplier settings. J8 and J15 are probably about the CPU's core voltage. It configures wether your voltage regulator will produce a different voltage for your CPU's core (like it was first required by Pentium MMX CPUs, this voltage is usually labelled Vcore) than it produces for the communication between CPU and northbridge. (This voltage is typically labelled Vi/o and uses ~3.3V in this CPU generation.)

The multiplier setting configures how fast the CPU core runs relative to the FSB (frontside bus, the communication between CPU and northbridge).
You are currently using the multiplier setting that a Pentium P54C will interpret as 1.5x FSB speed while a P55C or Tillamook (both Pentium MMX) will interpret the same setting as 3.5x FSB speed. Your FSB is set at ~75MHz. A regular Pentium will run at ~110MHz at this setting (1.5x75=112.5) and a Pentium MMX will run at ~266MHz when configured like that (3.5x75=262.5).

OK so I took the cpu off and its 266MMX 2.8V standard
Is it rare? Can I run it in 3.38v then?

idan182 wrote on 2022-03-23, 17:36:

OK so I took the cpu off and its 266MMX 2.8V standard
Is it rare? Can I run it in 3.38v then?

That's a regular 233MHz Pentium MMX. It is supposed to be run at 2.8V.
Change the J8 to J15, set the voltage jumper to 2.8V and see if that fixes your stability problems.😃

It's not particularly rare or valuable I'm afaraid but on the upside it probably didn't get damaged from being overvolted like a Tillamook would probably have.👍

It's a 233MHz pentium MMX. It's a normal CPU

I changed J8 to J15 and the voltage to 2.8v

It seem that if I connect my CF Drive it does that.
It won't recognize it at all, not in Primay IDE, and not Secondary. either Master or Slave.

I managed now to get the MASTER and SLAVE working. HD is Master, CDROM is Slave.
my DOS and everything is on the CF Card so I don't have a way to check but it does boot fine now until disk boot failure please insert disk and press enter.
Any suggestions for new CF Drive and not this Chinese?

why do I see 266mhz on post if my cpu is 233?