clownwolf wrote on 2025-04-09, 01:28:

My Motherboard has a maximum 100MHZ FSB and 8.0 multiplier. It cannot reach 133mhz FSB. Meaning I can put at most an 800Mhz P3 or Celeron on it.

On Ebay a Pentium III 800EB (133Mhz FSB x 6.0) is 3x cheaper than a regular Pentium III 800 (100Mhz FSB x 8.0) . Will the cheaper P3 800EB be stable if I run it with 100Mhz FSB and 8x multiplier (since my MB doesnt have 133Mhz FSB?)

Setting aside potential voltage and pinout constraints (there might be none, but I'm not trusting my memory on this and I have no idea what board you have), the main issue would be that the 800EB, like practically all newer P2/P3 CPUs has a locked multiplier of 6.0 , so it would run at 600MHz on your board.

However, a locked multiplier can be a net positive because it means that CPUs will ignore your board's multiplier setting (and its limitations).

What model board do you have ?

A-Trend ATC-6240 V2. It came with a Celeron-Only Slotket adapter.

So I guess I will have to buy the $50 dollar P3 800 (100Mhz FSB version) if I want the best CPU for this Board. Which is on top of a Pentium III slotket which I also need.

clownwolf wrote on 2025-04-09, 01:52:

A-Trend ATC-6240 V2. It came with a Celeron-Only Slotket adapter.

So I guess I will have to buy the $50 dollar P3 800 (100Mhz FSB version) if I want the best CPU for this Board. Which is on top of a Pentium III slotket which I also need.

Both the 133MHz and 100MHz FSB variants are FC-PGA in their socket 370 flavors. The "Celeron-Only Slotket adapter" you have might not support FC-PGA CPUs. Do you have a brand/model number for it or photos ? Were you planning on buying a slot 1 CPU variant or using that adapter or possibly getting another adapter?

https://www.cpu-world.com/CPUs/Pentium- ... 256E).html
https://www.cpu-world.com/CPUs/Pentium- ... 256E).html

Voltage wise, your board should be able to handle the lower voltage that Coppermine generation CPUs require, the only other concern would be potential lack on BIOS support for Coppermine CPUs, but which can probably be patched in .

I am planning to use the socket 370 version of the Pentium III 800, and just buy a new Slotket adapter. The Slot 1 version of PIII-800 is hundreds of dollars expensive so that's not an option.

Regarding the Celeron slotket, I bought this board ~20 years ago and I didn't use the Celeron Adapter at all, I replaced it with a Pentium II. I will be surprised if I still have that adapter somewhere in my house, since I was unreasonably dismissive about Celerons back then.

The main question was about the PIII-800EB version, but you already answered that question. I won't be getting it if it will be locked to x6 multiplier and run like a PIII-600. That speed would almost be a Celeron 800 at that point, and I would prefer the Celeron 800 instead.

clownwolf wrote on 2025-04-09, 03:29:

I am planning to use the socket 370 version of the Pentium III 800, and just buy a new Slotket adapter. The Slot 1 version of PIII-800 is hundreds of dollars expensive so that's not an option.

Regarding the Celeron slotket, I bought this board ~20 years ago and I didn't use the Celeron Adapter at all, I replaced it with a Pentium II. I will be surprised if I still have that adapter somewhere in my house, since I was unreasonably dismissive about Celerons back then.

The main question was about the PIII-800EB version, but you already answered that question. I won't be getting it if it will be locked to x6 multiplier and run like a PIII-600. That speed would almost be a Celeron 800 at that point, and I would prefer the Celeron 800 instead.

An 1100MHz, 128K L2 cache Celeron at (100MHz FSB) with a Coppermine core should work as well. https://www.cpu-world.com/CPUs/Celeron/ ... 0128).html with one of the common FC-PGA (Coppermine) capable slotkets. Whether that would usually be faster than an 800MHz 100MHz 256K L2 Coppermine P3 is a good question.

That brings us back to the motherboard problem right, It cannot go over 8x multiplier, so maximum is 800Mhz. Unless I am misunderstanding things and there is a way to increase it further?

clownwolf wrote on 2025-04-09, 06:33:

That brings us back to the motherboard problem right, It cannot go over 8x multiplier, so maximum is 800Mhz. Unless I am misunderstanding things and there is a way to increase it further?

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Unless you have an engineering sample processor, a Pentium III will always run at it's original multiplier regardless of what the board supports, because they are multiplier locked. If anything, the board's BIOS may report the wrong processor or speed, but a PIII with a 6x multi will always have a 6x multi. So, no matter what the board jumpers are set to, you will have whatever multiplier the CPU was built with. The multiplier jumper only pertains to unlocked chips and will do nothing at all with a PIII installed.

There may be other exceptions, but this has been my experience with them. On one hand it is nice because you generally don't have to worry about whether a board supports a certain speed of CPU as long as it supports Coppermine in general. On the other hand, it makes a PIII a lot less flexible for underclocking (for playing speed sensitive games) compared to a processor with an unlocked multi.

And, you may have figured this out by now, but this is exactly why a PIII coppermine with a 100Mhz FSB is so much more expensive than a 133.

darry wrote on 2025-04-09, 04:12:

An 1100MHz, 128K L2 cache Celeron at (100MHz FSB) with a Coppermine core should work as well. https://www.cpu-world.com/CPUs/Celeron/ ... 0128).html with one of the common FC-PGA (Coppermine) capable slotkets. Whether that would usually be faster than an 800MHz 100MHz 256K L2 Coppermine P3 is a good question.

The 1100 Celeron is at least 10% faster than the 800 fsb 100 Coppermine.
Finding a nice Coppermine slotket and installing a good cooling solution will require an investment that is not trivial.

clownwolf wrote on 2025-04-09, 01:52:

So I guess I will have to buy the $50 dollar P3 800 (100Mhz FSB version) if I want the best CPU for this Board. Which is on top of a Pentium III slotket which I also need.

Buy a cheap 1Ghz P3 and run it at 750 MHz. Problem solved. Although I'm no sure if this board has support for any Coppermine CPUs.

The Serpent Rider wrote on 2025-04-09, 07:45:

clownwolf wrote on 2025-04-09, 01:52:

So I guess I will have to buy the $50 dollar P3 800 (100Mhz FSB version) if I want the best CPU for this Board. Which is on top of a Pentium III slotket which I also need.

Buy a cheap 1Ghz P3 and run it at 750 MHz. Problem solved. Although I'm no sure if this board has support for any Coppermine CPUs.

Yeah, that is a good way to go, but as you said, upon looking up the board it is unlikely that it supports coppermine:

https://theretroweb.com/motherboards/s/a-tren … -v2-pcb-rev-r05

backside of the motherboard near the DIMM slots gives PCB rev, only R06 has Coppermine support

Another indicator is if you can find the voltage regulator chip for the CPU and look up the part number on it. If the datasheet says it goes down to 1.3v, then a Coppermine will likely work. If it says it goes down to 1.8v then you cannot use a Coppermine on the board without a very fancy slotket that can overcome that limitation.

I think the Pentium III had the most slot/socket types of any CPU and nobody ever seems to remember them.
They all get conflated into just the two. Slot 1 and socket 370.

My advice to the OP.
Stop chasing the speed and enjoy what you have.
Put a slot 1 Pentium III /100 in there and see what it can do.

Then if it cant play "that" game then start over again and enjoy the journey.

After several days of thinking about the overall costs of Pentium IIIs, I think I will just focus on the Celerons of this era (Win98SE).

Considering the motherboard itself, I will just stick a Celeron-Mendocino on this one to avoid potential headaches. I already have plans for the next 2 Celeron projects (Coppermine-128, Tualatin-256) after this.

clownwolf wrote on 2025-04-13, 21:10:

After several days of thinking about the overall costs of Pentium IIIs, I think I will just focus on the Celerons of this era (Win98SE).

Considering the motherboard itself, I will just stick a Celeron-Mendocino on this one to avoid potential headaches. I already have plans for the next 2 Celeron projects (Coppermine-128, Tualatin-256) after this.

The attachment Screenshot 2025-04-13 140627.png is no longer available

Slotket modification is quite a fun rabbit hole if you're that way inclined

https://krick.3feetunder.com/370mod/

https://web.archive.org/web/20060312234446/ht … ps630/index.asp

I'd only do it with fairly cheap celerons though, just in case 😉

PARKE wrote on 2025-04-09, 07:44:

darry wrote on 2025-04-09, 04:12:

An 1100MHz, 128K L2 cache Celeron at (100MHz FSB) with a Coppermine core should work as well. https://www.cpu-world.com/CPUs/Celeron/ ... 0128).html with one of the common FC-PGA (Coppermine) capable slotkets. Whether that would usually be faster than an 800MHz 100MHz 256K L2 Coppermine P3 is a good question.

The 1100 Celeron is at least 10% faster than the 800 fsb 100 Coppermine.
Finding a nice Coppermine slotket and installing a good cooling solution will require an investment that is not trivial.

I guess prices have gone up since the last time I looked and stocked up. 🙁

Even with voltage regulator supporting at least 1.8V you could still run Coppermine, but I would check the real voltage to be safe. You would have to do a mod to make the motherboard think 1.8V was requested.

The cheapest way to test it is to buy the fastest Coppermine Celeron. It will be effectively about 250-300Mhz slower in games than a regular PIII, but PIII 750 is fast enough for Windows 98.

Getting the fastest PIII Katmai 600Mhz is also not a bad idea.

This particular board was fortunately revision R06, so the voltage does come down all the way to 1.5v

Also PIII prices doesn't seem to be bad after some more browsing. I bought a bunch of S370 PIII Coppermines of various speeds, alongside some Coppermine slotkets.

I also bought a couple of combination Slot1/Socket 370 motherboards (J-993AN). I think their redundancy are a great value since I already once accidentally snapped off a Socket 370 heatsink tab.

I was initially only interested in collecting pre-Pentium era hardware, but I think its time to focus on Win98SE hardware before they become rare.

J-993AN is VIA VT82C693A though, it will have terrible memory performance. It can be partially fixed by enabling some "beta" chipset features in wpcredit during Windows startup. There is no fix for DOS.

My ECS P6BXT-A+ is a Slot1/Socket 370 combo board, but an older revision supports only PPGA CPUs in Socket 370. Coppermines work fine in Slot1. You may run into such issues on combo boards.

Windows 98SE hardware is not expensive as long as ISA is not required.

AlexZ wrote on 2025-04-16, 07:31:

J-993AN is VIA VT82C693A though, it will have terrible memory performance. It can be partially fixed by enabling some "beta" chipset features in wpcredit during Windows startup. There is no fix for DOS.

My ECS P6BXT-A+ is a Slot1/Socket 370 combo board, but an older revision supports only PPGA CPUs in Socket 370. Coppermines work fine in Slot1. You may run into such issues on combo boards.

Windows 98SE hardware is not expensive as long as ISA is not required.

Both my 370 boards are Apollo Pro 133T, so while not optimal, I think I can tolerate the Apollo Pro 133A for the slot1/370 combo boards. For pure Slot 1 I will definitely check first and avoid the Via Apollo chipsets.

ISA slots are a must for me, since I invested a good amount of money in ISA sound cards and wavetable clones a while back.