Which Pentium II can be multiplier underclocked?

[Gerwin]

For retro games I would like to have the option to fit the potentially slowest Slot 1 Pentium/Celeron CPU. Or socket 370 CPU on a slotket adapter.
Normally this would be a PII 350/100 -> 233/66MHz. Or PIII 533/133 -> 266/66MHz.

But I would like to go slower, and wonder if certain CPU's can accept a lower multiplier then their default, like 1.5x. For now I confirmed that the following CPU's are totally ignorant of any lower multiplier setting: PIII 600 'SC242', PII 350 'SL356', Cel 300 'SL2YP'.

Anyone know of suitable part number that has a better chance of accepting a 1.5x multiplier?

Thanks in advance.

[Guest]

pre 1982... wrong part of the forum.. I am sorry.

[CPUShack]

no worries moving now....

[frag_]

Gerwin
It's well known what intel start to lock the multiplier since august 1998.
All pentiums II produced before this data must be unlocked.
There are Klamath 233, 266, 300
and some early 266, 300, 350 Deschutes.
So try to obtain 233 or 266 variant.
I don't remember the lovest possible multiplier,
may be 1.5, it gives 66x1.5=100 MHz,
and some boards can adjust lower fsb

[Gerwin]

Thanks frag,
I read about the august 1998 issue before, but some sources say earlier processors are not unlocked, but 'Multiplier Limited'.
However:
The PII 350 SL356, is marked (c) 1997. The Cel 300 SL2YP, is marked 9821 on the top right of the PCB, which I imagined to mean week 21 1998? I bought it in september 1998. And I found these to be locked. Now I don't know which marking is the actual manufacturing date. So how to be more sure?

Indeed, some 440BX mainboards have a setting as low as a 1.5x multiplier, but most have a minimum of 2x or 3x.

[Gerwin]

I read somewhere an early stepping number might be an indication, I'll try a PII 350 with stepping dA1 then...

[frag_]

IMO simplest way is to find PII 233, it must be unlocked.
BTW why pentium II and not a Pentum MMX ?

[Gerwin]

I know For serious early 90's retro gaming and tweaking I would better assemble a 486 or 386. But I don't feel like doing so at the moment. So I would like to stick to experimenting with my 440BX chipset mainboard (slot-1). A 2.8 Volt 233MHz CPU would be the safest bet indeed, but an early 2.0 Volt 350 MHz CPU should give a bigger speed range to choose from and stay cooler still. Just my thoughts..

[Gerwin]

To conclude this topic:

I did not buy the 350. I bought an SL2QF instead, Being a Pentium II 333MHz, 66MHz FSB, with MMX, Deschutes Core, 2.0 Volt, 512kB L2 cache at half speed. It is a retail processor in a solid plastic cartridge with a nice but worn Intel fan. I put it in a mainboard from Aopen, the AX6BC revision 1.4, it has a 440BX chipset.

Multiplier 5.0x, FSB 66MHz -> CPU runs at 333/66MHz, default setting.
Multiplier 1.5x, FSB 66MHz -> CPU protests* and runs at 133/66MHz instead.
Multiplier 2.0x, FSB 66MHz -> CPU runs at 133/66MHz.
Multiplier 5.5x, FSB 66MHz -> CPU protests* and runs at 133/66MHz instead.
Multiplier 4.0x, FSB 100MHz -> CPU runs at 400/100MHz, temp. is OK.
*CPU protests: warm rebooting does not work in this case.

All other Pentium II/III/Celeron CPU's I have around here do only their default multiplier. So this P-II 333 is one of the most flexible types of Pentium CPU's. It accepts multipliers ranging 2x to 5x, the so called 'multiplier limited' Pentium. It has a speed range of 133 to at least 400 MHz.