In general, yes.
However, the Intel motherboards I'm familiar with are very pedantic about their maker's compatibility specifications and unless I'm mixing up something in my memory, I think they will refuse to do this. They will just say the CPU is unsupported and tell you to get lost.
There might be some prebuilt systems that act that way as well. I have an IBM workstation board that I expect would be stubborn about it (but I haven't tried trolling it in this particular manner).

But if it's a non-Intel board that was typically marketed for home builds (Asus, Gigabyte, FIC, etc etc) then yeah it will work as you describe. Those board makers had no desire or incentive to be difficult about this, so they aren't.

With a 440BX there can sometimes be issues with Coppermine voltage support and BIOS compatibility, but if you know your board to support these things then what you describe should work fine.

Depends...

Exactly which CPU is it? And which motherboard (+ revision)?

A P3-866EB is a CPU with a Coppermine core. For the CPU to work, the board needs to support Coppermine CPUs and (more importantly) the 1.8V core voltage they require. Not all i440BX boards do that. Assuming the board supports Coppermines, it should work, and running at 100MHz FSB you would get 650MHz.

However most i440BX boards were happy to run at 133MHz anyway. But the i440BX doesn't have a 1/2 AGP divider, so at 133MHz FSB you will be running the AGP port at 88MHz. Not all cards like that. Moreover some older/OEM i440BX boards don't support a 1/4 PCI divider, so would be running the PCI bus at 44MHz as well. That is almost certainly too fast for most (integrated) IDE controllers, so even if chipset, memory, CPU and AGP are fine with 133MHz FSB, if your board can't do 1/4 PCI divider you are likely to be stuck.

But no reason not to try. My Packard Bell / MSI MS-6168 board is about as OEM as they come, with uATX form factor, i440BX chipset and a Voodoo3 onboard, but with a retail Award BIOS it allows clocking up to 133MHz FSB, and offers 1/4 PCI divider. So pair it with the right CPU and RAM, and it happily runs at 133MHz FSB, with my P3-600E thinking it's a P3-800EB 😉

It is a Dell dimension R350 and PIII SL47S 866MHz

"Dell Dimension R350" is the name of the system, not the motherboard. That R350 probably contains some or other version of the Intel 'Seattle' SE440BX motherboard. Given that the P2-350 is the very first 100MHz FSB P2 and so the oldest CPU to be paired with an i440BX I wouldn't get your hopes up for Coppermine support, but to be sure you'd need to tell us the exact model # and revision of the motherboard.

Dell is also famous for wanting you to buy a new computer for a new generation of CPU's, they have a wonderful track record of it in fact.

candle_86 wrote:

Dell is also famous for wanting you to buy a new computer for a new generation of CPU's, they have a wonderful track record of it in fact.

Dell is an OEM and doesn't actively support customers messing around inside their computers - something no OEM does because of the support implications. If you want that, build your own. But there's a big difference between not supporting and actively hindering. The only really nasty thing they did was mess around with power supply pinouts meaning that swapping motherboards was non-trivial. But the motherboards themselves were pretty standard devices and in no way limited versus similar ones available retail at the time. With the right SE440BX revision you could just as easily run a 1GHz Coppermine CPU as you could on a retail Asus P2B. However that P2B would also only run them from rev. 1.12 onwards, and the same applies to the SE440BX. So instead of FUD, we need to find out exactly which board is in there.