AlexZ wrote on 2026-03-30, 16:51:

CUBX is a 133Mhz FSB board, 1Ghz@133 is the best choice. It may be possible to run it at 500Mhz with 66Mhz FSB. 100Mhz FSB versi […]
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pete8475 wrote on 2026-03-27, 22:08:

I might buy a 100mhz fsb P3-900 and see if I can get that stable at 1.2. That way everything is in spec except agp (this card is fine with 89mhz agp) and it obviously would downclock nicely to 600mhz (66mhz fsb) as well.

CUBX is a 133Mhz FSB board, 1Ghz@133 is the best choice. It may be possible to run it at 500Mhz with 66Mhz FSB. 100Mhz FSB versions suffer from FSB overload at about 900Mhz and higher.

My PIII 900 is enough for the whole Windows 98 era and very early Windows XP (~2002).

fx5900xt is for P4/Athlon XP/Athlon 64 (s754). If you want to max it out in Windows 98 then get Athlon 64 with AGP. GeForce 4200ti is a good match for PIII.

H3nrik V! wrote on 2026-03-29, 06:41:

The thing with 900/100s is that there were never sold many back in the day, I have yet to come across one for a price, I'm comfortable paying ..

That's why I got an extra PIII 900 while they were cheaper. I have also seen 1.1Ghz@100 on sale, but those are even more rare.

The best CPU for this board is the P3 1.4S I have, but this isn't about having the fastest P3.

That CPU isn't quite fast enough so I use a P4 overclocked to 4.75GHZ for the later DX9 era stuff, I just want something a little more versatile for old stuff so I've ordered on ebay a 900 and we'll see if it'll do 600, 900 and 1200mhz.

EDIT - also 133FSB 1GHZ Pentium 3 does work at 500 in this board.

I couldn't find a Coppermine that would reliably clock past about 1100 on my Intel Seattle board. Even the Celeron 1100 that I had would lock up and freeze.
Ended up with a cheap slocket and a pin modded Tualatin 1266.
Eventually moved on the just using my Intel 815 board with the same chip.
It is fast and trouble free.

AlexZ wrote on 2026-03-30, 16:51:

H3nrik V! wrote on 2026-03-29, 06:41:

The thing with 900/100s is that there were never sold many back in the day, I have yet to come across one for a price, I'm comfortable paying ..

That's why I got an extra PIII 900 while they were cheaper. I have also seen 1.1Ghz@100 on sale, but those are even more rare.

Makes sense. By an incredible strike of luck, I've gotten my hands on a pair of 1.1/100. Both working - for my P2B-DS. (All though a pair of native 1000/100 Slot1 would be even cooler)

Having built many BX and 815 builds with Tualatins, I only kept one 815 1.4S build (CUSL2) so that I can run Voodoo5 at normal AGP speed (it ran fine at 89 MHz I don't want to shortne its lifetime).
For all other Tualatin builds I have (including P2B-D dual etc) I use either BX or i840 (Compaq AP550/OR840).
BX is just much faster than 815, like hot-rodding a car.

Paadam wrote on 2026-04-06, 19:09:

Having built many BX and 815 builds with Tualatins, I only kept one 815 1.4S build (CUSL2) so that I can run Voodoo5 at normal AGP speed (it ran fine at 89 MHz I don't want to shortne its lifetime).
For all other Tualatin builds I have (including P2B-D dual etc) I use either BX or i840 (Compaq AP550/OR840).
BX is just much faster than 815, like hot-rodding a car.

Alas, this is only at first glance.
The 440BX chipset lacks dividers for a 133 MHz memory frequency (it only has a 1 configuration bit – 66/100 MHz), so it operates with ‘hidden memory overclocking that cannot be disabled’
Consequently, users will either have to choose from a wide range of stick or purchase a CL2 memory stick straight away.
Virtually any decent PC133 memory stick on an I815 chipset works perfectly with 2-2-2-5 timings.
(A CL2 stick — even at 150 MHz — uses precisely these timings).
Therefore, an I815 with a 440BX memory kit and the appropriate settings will perform at least as well.
And at 150 MHz — significantly better.
The only significant drawback of the i815 is the 512MB limit; it’s hard to argue with that.

really more people should consider i820 plattforms. Only the one with SD-Ram translator chip made problems. the RD-Ram models were fine
The Asus P3C-E was widely availabe and cheap back then and is rock stable. RD-Ram is easy to get and cheap now adays.
If you dont use an ISA Soundcard this is a good plattform. And takes Tualatins via any modified Slot 1 Adapter.

If you don't want ISA there are better options. It's more for people who specifically want RDRAM.

voodoo5 wrote on 2026-04-07, 09:00:

really more people should consider i820 plattforms. Only the one with SD-Ram translator chip made problems. the RD-Ram models were fine
The Asus P3C-E was widely availabe and cheap back then and is rock stable. RD-Ram is easy to get and cheap now adays.
If you dont use an ISA Soundcard this is a good plattform. And takes Tualatins via any modified Slot 1 Adapter.

If you read my posts, it’s immediately clear that I’m categorically biased against VIA chipsets for Socket 370.
That’s because I began my x86 journey with a VIA Apollo 133 manufactured by PCpartner. 😀
Many years on, it’s starting to seem to me that a motherboard from a decent manufacturer based on the VIA 694 with 4 RAM slots is almost the best choice for this platform.

PS
Given that the Pentium Tualatin is already often more expensive than the first-generation Ryzen...

i820 is not a via chipset. its intels successor for 440bx. and i must correct myself: the Asus P3C-E even has an isa slot. it takes up to 1GB of Rambus and has 133mhz fsb.
i had i820 with tualatin and i ran perfectly. of course any other PIII is also usable.

shevalier wrote on 2026-04-07, 11:49:

If you read my posts, it’s immediately clear that I’m categorically biased against VIA chipsets for Socket 370. That’s because I […]
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If you read my posts, it’s immediately clear that I’m categorically biased against VIA chipsets for Socket 370.
That’s because I began my x86 journey with a VIA Apollo 133 manufactured by PCpartner. 😀
Many years on, it’s starting to seem to me that a motherboard from a decent manufacturer based on the VIA 694 with 4 RAM slots is almost the best choice for this platform.

PS
Given that the Pentium Tualatin is already often more expensive than the first-generation Ryzen...

I stayed with Intel CPUs since the Pentium 4 days, to be able to stay with Intel chipsets. Had a really bad experience with a P4 board and SiS chipset, so I really get your point!