A few things to keep in mind:
- the ram should be happy at 83MHz (PC100 or pc133 with 8 or 7.5ns chips would be perfect)
- the motherboard and it's chipset should be happy at 83MHz
- some PCI cards don't like the overclocked PCI bus: 66/2=33MHz PCI, 75/2=38MHz PCI, 83/2=42MHz PCI and lots of cards are unhappy at those speeds.
- cooling must be upgraded (any smaller socket A cooler will do)

I have several pentium 166 and 200 that all run great at the 83 and 95MHz bus speed. Also a lot of MMX that all (without exception) run stable at the 100MHz bus speed (some stunning happy over 300MHz). All are tested this way on a super 7 board so the board could not be the limiting factor. So in my opinion the board could be the limiting factor here.

can you bump vcore?

rasz_pl wrote on 2024-06-23, 18:16:

can you bump vcore?

Good point. The MMX will run much more stable with a little more volts when overclocked. 2,9 or 3,0V is probably what it needs and wont harm the cpu.

Verdorie1 wrote on 2024-06-23, 15:04:

What I've noticed is that at the stock speed of 233MHz the CPU performs a bit worse in games than the old one at 225MHz.

That’s because the FSB and PCI-bus run faster at 225MHz.

however running it at a 3x multiplier at 83MHz bus (250MHz) runs completely fine.

so run it at 250MHz! 😀 Especially with your observation that the 225/75 configuration can be faster than 233/66. Imagine what 250/83 will do against 262/75. I’d personally would settle with the 83FSB option 😀 (I used to run a Pentium with 83FSB back in the day, ran very nice with a Voodoo Graphics card 😉)

If you do want to aim for a bit more MHz then just increase the vCore by 0.1 or 0.2v as mentioned by others.

Thandor wrote on 2024-06-23, 19:00:

so run it at 250MHz! 😀 Especially with your observation that the 225/75 configuration can be faster than 233/66. Imagine what 250/83 will do against 262/75. I’d personally would settle with the 83FSB option 😀 (I used to run a Pentium with 83FSB back in the day, ran very nice with a Voodoo Graphics card 😉)

Yeah that would be my next worry, I want to slap a Voodoo 1 in it and I'm not sure how it plays with 83MHz FSB

In my experience, PCI graphics cards are never the deal-breaker on overclocked systems. Sound, drive controller, lan... They are the more common pains. Scsi on first.

Verdorie1 wrote on 2024-06-23, 15:04:

So recently I picked up an old socket 7 PC and I've been messing around with it. Originally it came with a 200MHz Pentium MMX. I […]
Show full quote

So recently I picked up an old socket 7 PC and I've been messing around with it. Originally it came with a 200MHz Pentium MMX.
I decided to try to do some overclocking so I upped the bus speed to 75MHz for 225MHz total (83MHz wouldn't POST).
Last week I ordered a Pentium 233 MMX and I want to run it at a 75MHz bus too for a total of 262.5MHz.

What I've noticed is that at the stock speed of 233MHz the CPU performs a bit worse in games than the old one at 225MHz.
Here's where I ran into problems, running this CPU at 262.5MHz causes instability and Windows 95 doesn't boot properly however running it at a 3x multiplier at 83MHz bus (250MHz) runs completely fine.
Upon starting it immediately shows a blue screen with VXD error codes and some times doesn't even get that far before turning off completely.

Have I just gotten unlucky in the silicon lottery? Will buying another 233 give me a chance at running a stable 262.5MHz or even at 291MHz?
Or is there some other issue at hand.

I've already tried swapping my video card and RAM at 262.5MHz but that didn't solve anything.

If you want a mmx that will run at high clocks, try a tillamook ppga

Many p55 will do 250 most will not get close to 300

But every tillamook ppga I have tried will do 300 many will do 400

The catch is mods, and 2.0v core

The tillamook will have a 4x multi btw. (Mods required)

As if the Tillamook would be so easy to get compared to a common Pentium MMX.

Anyway, trying to be useful... there are 2 variables in this Socket 7 overclocking:
Increase the fsb overclocks the full system as someone mentioned, leading to a higher performances even if the final clock is lower (pci clock is higher, cache speed is higher, memory is faster), but it's not always achievable to have a stable system with 83 mhz fsb.
The cpu may not tollerate such high overclock, that would explain why 250 is ok but 266 is not.

Without going for any exotic advice which is surely expensive (more than use a cpu you already have, interposer, modify the cpu etc)... go for 83x3 you will achieve the best performance with the lowest effort.

Nemo1985 wrote on 2024-06-23, 21:38:

As if the Tillamook would be so easy to get compared to a common Pentium MMX. […]
Show full quote

As if the Tillamook would be so easy to get compared to a common Pentium MMX.

Anyway, trying to be useful... there are 2 variables in this Socket 7 overclocking:
Increase the fsb overclocks the full system as someone mentioned, leading to a higher performances even if the final clock is lower (pci clock is higher, cache speed is higher, memory is faster), but it's not always achievable to have a stable system with 83 mhz fsb.
The cpu may not tollerate such high overclock, that would explain why 250 is ok but 266 is not.

Without going for any exotic advice which is surely expensive (more than use a cpu you already have, interposer, modify the cpu etc)... go for 83x3 you will achieve the best performance with the lowest effort.

https://www.ebay.com/sch/i.html?_nkw=sl2z4&_t … 752.m4084.l1313

https://www.ebay.com/sch/i.html?_nkw=sl2z3&_t … 311&_odkw=sl2z4

https://www.ebay.com/sch/i.html?_nkw=sl2zx&_t … 490.m4084.l1313

Choose your model.

166, 233, 266 (don’t believe 200 exists)

As of this posting all are for sale and easy to find in those links. Ranging from $23 to $96

Many socket 7 motherboards support 2.1v core voltage. This is low enough for tillamook.

Tillamook 266MHz and working L2 cache?

Thank you for confirming that the price for such cpus are crazy compared to the common Pentium MMX, let me correct your statement about "many socket 7 cpu supports v2.1", nope they don't some SUPER SOCKET 7 motherboards may support such low voltage... the user who opened the topic clearly has a Socket 7 motherboard, which they usually just go down to v2.8.

Nemo1985 wrote on 2024-06-23, 22:56:

Thank you for confirming that the price for such cpus are crazy compared to the common Pentium MMX, let me correct your statement about "many socket 7 cpu supports v2.1", nope they don't some SUPER SOCKET 7 motherboards may support such low voltage... the user who opened the topic clearly has a Socket 7 motherboard, which they usually just go down to v2.8.

motherboards*
You aren’t correcting anything. Many socket 7 motherboards have settings that go down to 2.1, this is well known among many board owners in the community. Many of these boards can be made to run k6-3+ cpus a trip to Jan’s website can teach you about how many are supporting this.

Many socket 7 mobos have a voltage jumper config like this

+0.1v
+0.2v
+0.4v
+0.8v

-2.8v is usually the last jumper,
-all off or only the first one is usually the lowest voltage often 2.1v
-all on is usually 3.3-3.5v

23$ isn’t expensive in today’s market, it’s actually cheap for a socket 7 cpu most boring socket 5/7 cpus on ebay go for 20-30$ I buy one or two a month to grow my collection.

The voltage support is hardware and not software, the bios can recognize the cpuid string, which doesn't make it compatible from the voltage point of view. Most of the bios Jan has modified are for super socket 7 boards not socket 7.

Can you quote some of those "many" socket 7 mobos that you mention, oh yes other than the Asus P55T2P4, or the Asus TX97-LE?
Most of the oldest socket 7 board they barely support the dual voltage without the added module.

Sorry, that’s a bit of a ridiculous ask. I haven’t made a comprehensive list for you, I could start digging through my collection and mapping out jumpers for you but I am not going to do that.

But from ones that I can recall off hand I have my tyan s1546, iWill p55xb2, and several others I don’t recall models of. (In my possession) I actually can’t think of a s7 mobo that I own that doesn’t do this, but I may have one if I look.

As I said, Jan’s site is full of socket 5/7/ss7 boards that have updated bioses to support k6-3+ on the site he talks about how many s7 boards support 2.1v this is often undocumented, my tyan supports down to 1.6v btw. It is a socket 7 board. Not a ss7.

It’s the socket 5 boards that basically always need interposers. Socket 7 very often can support 2.1v (but not always) you just can’t make a blanket statement about socket 7.

There are even socket 7 mobos that need a interposer or VRM for a 2.8v cpu.

Yes, many support 2.1v

If OP would be so kind as to post a pic and a model number we could look into this one.

waterbeesje wrote on 2024-06-23, 20:11:

In my experience, PCI graphics cards are never the deal-breaker on overclocked systems. Sound, drive controller, lan... They are the more common pains. Scsi on first.

1994 and 1995 graphics chipsets might be a bit more finnicky and the cheaper cards, '96 and 97 Virge DX, Trio 64V etc usually alright.

Sphere478 wrote on 2024-06-24, 00:32:

If OP would be so kind as to post a pic and a model number we could look into this one.

The board I'm using is a Lucky Star 5I-TX1.
I'm not able to take a picture right now but this is the one: https://theretroweb.com/motherboards/s/lucky- … x1-rev-1.31-2.0

I am running 2x32MB PC-66 168-pin SD-RAM, a PCI Matrox Millennium II 4MB and a Sound Blaster Vibra 16C (which I want to swap for another AWE64 like my other PCs).
I am not using any other expansion cards at the moment like networking however I do want to get a Voodoo 4MB for this PC

It seems the ABiT AB-PX5/AX5/TX5 according to manual, in later revisions support from 2.2 to 3.3V for VCore.

Yeah, going off the picture on the retroweb that has the jumper block I was talking about. Without looking at manual, Pictured it seems to be set up for 2.8v moving that last jumper off will probably give around 2.1v give or take.

This is a 430tx chipset supporting 256mb of ram with any processor, but slow with anything except k6-3/k6-3+/k6-2+ those cpus will not slow down with that much ram, othet cpus should probably be set up for 64mb of ram or less.

Your maximum windows version is actually windows 7 as the south bridge supports acpi

Max fsb is probably 75 or 83

A good card set is

Promise tx4
Radeon 9200/7500/9250
Sb16 or audigy 2zs

I don't know if there is something weird about the 430TX but I have had several that don't like 83Mhz much, while in comparison 430HX and 430VX have been fine with it. I would put the blame on the IDE controller, but it's the same as on PII 440LX isn't it? and those don't seem to give the same problem. Also putting a PIO mode drive on it doesn't seem to make a difference. (i.e. stress the DMA part less) I have thought of putting a thread up a few times "What the hell is up with 430TX boards??" but I don't have one running at the moment for testing, and I might just have unlucky examples.