I'm finding the matter is further complicated as it seems 1gh p3 xeons use rambus memory. They also have a 133mhz bus, the 700mhz p3 has 100mhz bus.

The memory depends on the motherboard and so might the clocking options, which motherboard and exactly which P3 Xeon CPUs do you have?

One example of an underclocked Xeon is Re: In an SMP system how does DOS/98 choose the CPU to utilise?

I have neither at the moment. As stated the cpu/s are slot 2 p3 xeons 1ghz clock 133 bus speed. The mobo is an 8682 IBM xseries 350 quad cpu board. The board is supposed to run at 700mhz with a 100mhz bus.

I suspect a 1GHz/133 MHz Xeon will run at 750 MHz, but you will probably only be able to use two. If I had an 8682 IBM xseries 350 quad CPU board I would try and get some 700 or 900 MHz 100MHz FSB CPUs.

Looking at the MB Manual Table 10 then I expect other ratios are possible. Further it has SDRAM rather than RDRAM

So the rambus issue is a function of the chipset apart from the cpu, or do certain cpus/chipsets (which would mean.the cpu itself) mandate rambus memory? Iow do 1ghz p3s have to have rambus irrespective of what they're running in?

More modern boards seem to run with xeons or core series, especially sff HPs from a few years ago (c602 chipsets iirc, I could be wrong though). So if you updated the bios and dropped a xeon in a board formerly populated with an i5,i7, would you have to also upgrade to ecc memory? You'd probably want to, why run a xeon otherwise. Even socket 775 boards had xeons as an option, and I'm not talking about that weird hack.

chris2021 wrote on 2021-12-28, 12:43:

So the rambus issue is a function of the chipset apart from the cpu, or do certain cpus/chipsets (which would mean.the cpu itself) mandate rambus memory? Iow do 1ghz p3s have to have rambus irrespective of what they're running in?

More modern boards seem to run with xeons or core series, especially sff HPs from a few years ago (c602 chipsets iirc, I could be wrong though). So if you updated the bios and dropped a xeon in a board formerly populated with an i5,i7, would you have to also upgrade to ecc memory? You'd probably want to, why run a xeon otherwise. Even socket 775 boards had xeons as an option, and I'm not talking about that weird hack.

Nope, ECC is not needed.

A lot of the reason to run the LGA1366, 2011, and 2011-3 Xeons is because of:
lower cost
unlocked (16xx series)
higher top speed
higher core count - LGA-2011 has the 1680 v2 available which is an 8-core 16-thread which more cores and threads than a 4960x.

Large cache Xeons run whatever you feed them. They are just specified to run at 100 MHz bus by Intel and small cache ones are specified to run at 133 MHz FSB.

I have ran PIII Xeon 700/2M/100 easily at 133 MHz FSB on my Asus XG-DLS, I tested from 4-7 (533-933 MHz) and it worked well even without touching vcore. Large cache Xeons have unlocked lower multipliers.
But no matter what I could not get the board to POST with both CPU's running at 133 MHz (even at lower multis), not sure whether it required higher voltage somewhere or what. Since both CPU's worked perfectly in single mode the problem is somewhere in chipset.

Paadam wrote on 2021-12-28, 18:59:

Large cache Xeons run whatever you feed them. They are just specified to run at 100 MHz bus by Intel and small cache ones are specified to run at 133 MHz FSB.

I have ran PIII Xeon 700/2M/100 easily at 133 MHz FSB on my Asus XG-DLS, I tested from 4-7 (533-933 MHz) and it worked well even without touching vcore. Large cache Xeons have unlocked lower multipliers.
But no matter what I could not get the board to POST with both CPU's running at 133 MHz (even at lower multis), not sure whether it required higher voltage somewhere or what. Since both CPU's worked perfectly in single mode the problem is somewhere in chipset.

That's the opposite of what I'm asking though (I think). You ran lower speed xeons at greater speeds. OK hopefully the converse applies. I have to count my pennies and see what I can buy this week. And give it a go.

Anyone with an Intel board that specs 1ghz slot 2s?

chris2021 wrote on 2021-12-28, 12:43:

So the rambus issue is a function of the chipset apart from the cpu, or do certain cpus/chipsets (which would mean.the cpu itself) mandate rambus memory? Iow do 1ghz p3s have to have rambus irrespective of what they're running in?

P3 (Xeon) CPUs don't communicate directly with RAM but with an AGTL(+) FSB. The northbridge connects to that and contains the memory controller for whatever type of RAM it supports. So there's no sich thing as a "Rambus CPU" at any speed. It all depends on motherboard chipset. P3 (Xeon) and Rambus usually means Intel i820 or i840 Chipsets, although there might be more exotic stuff in server world. Both are RDRAM only Chipsets, although both were originally intended to be able to support SDRAM too - with terrible performance - using an MTH before the MTHgate (Intel admitting MTH was fundamentally unstable and unreliable) forced Intel to recall all MTH boards.

OK good to know.

But as to the original question, should the 1ghz cpu work?

Of course you can run 1GHz PIII Xeon at 100 MHz FSB, it will just run at 750 MHz. I don't consider the small cache PIII Xeons as Xeons, they are really just a Coppermine core PIII's in Slot2 cartridge.

So I bought 1 of those mobos off ebay. It's huge ish and kind of beautiful. 15 5/8" x 15 3/8", roundabout. I don't have an atx board or case to peruse at the moment, so don't know if the holes match the atx format at all (wouldn't matter as even an ssi eeb compatible case would have portions of the case beyond the mobo area that are raised above the mount points. I have contemplated modifying cases for boards about that size, actually larger, but needless to say, although doable, there's a lot to do). It does appear to use the same 24 pin atx connector that my Intel SCB2 board uses (another p3 server but not slot 2 (or 1), and I have powered it with a recent atx p/s.

Although these are advertised as new-bulk packed, this one had a wrinkly bag. Perhaps other purchases will be newer looking then this one. Can't say:

https://www.ebay.com/itm/292673128668

And he raised the price from 10$ to 25$, and shipping (for me) from 10$ to 15$. Good luck with that buddy. Didn't sell any at 10$ u til I came along.

And just bought 4 possibly incompatible cpus. I have pertinent server memory already, I think. We will see what happens.