foil_fresh wrote on 2021-11-21, 22:27:

Asus P2b and LuckyStar 6abx2v. The Asus needs jumpers to set multi yet the Lucky star can change all settings in BIOS.

Thank you! It looks like rev 1.2 of Lucky Star is the one widely available on ebay. I am guessing yours is the same rev.

gerwin wrote on 2021-11-21, 23:27:

weedeewee wrote on 2021-11-20, 17:36:

Just looking at the manual for an abit be6-II and it lists a 1.5x multiplier.
Though, I have no idea which, if any cpu supports this.
Thought I'd mention it since everyone here lists 2x as the lowest possible multiplier

Maybe some exotic test sample once did 1.5x multiplier in an Abit lab. But normal Pentium IIs cannot do that, 2x is the lowest.

Got curious and found this via some googleing :
https://www.pchardwarelinks.com/cpuspeed.htm

PARKE wrote on 2021-11-22, 13:41:

Got curious and found this via some googleing :
https://www.pchardwarelinks.com/cpuspeed.htm
clock3.jpg

Indeed Interesting and confusing when I compare it to the dipswitch settings for the abit be6-II... which in itself is a bit confusing since it mentions 2x twice 😀

The table above also has a double listing for 2x (all low & all high) which is the same as in the Intel specsheet for Pentium Pro.
The clock multiplier on your board is maybe a different design. Can you see what marking is on the chip ? The datasheet may provide answers.

PARKE
I was just comparing the table you posted with the table in the mainboard manual to see if there was any correlation wrt the multiplier. Nothing to worry about.
Though if you want to dig down a rabbit hole, I won't/can't stop you.
FYI, the Clock synth on the be6-II is a RTM-520-39D

I'm not worried, just curious if a board with 1.5 multi boots with an unlocked Deschutes. It does not seem a common combination and I don't think I have ever read about somebody trying it.

PARKE, at the moment there's a SL356 installed, seems to be deschutes though I have no idea if it's locked or not... though given the oddness I recently had with the board, it might very well be.

I'll give it a boot with a different multiplier.

We -have- to know, right ? 😀
Btw, RTM-520-39D is a frequency generator. Unless it has a PLL on board it is not the chip that 'produces' the multipliers. Is there a smaller chip with 4/8/10 legs in that region ?
ps
SL356 is a later fsb 100MHz Deschutes. An older 66MHz version is probably needed for this.

PARKE? i'm confused. clock multiplier chip on a PII mainboard? Wouldn't that be integrated into the slot1 package or chip itself ?

if not... what model# of chip would I be looking for, for example?

Well, it clearly isn't unlocked, setting it to any other multiplier just makes it boot at 350MHz

Something like this:
https://www.renesas.com/eu/en/document/dst/511-datasheet

Forget it,
The clock multipliers are inside the Pentium II CPU. The PLL chip on the motherboard is for bus speeds, from there the FSB speed is multiplied in the Pentium 2.
I tried all the 16 possible settings with the 4-way DIP switch. Booted up and noted the result. Like I did for many CPUs. There is no 1.5x. Not for Klamath core and not for Deschutes. Klamath core has 2x multiplier with working L2 cache, Whereas Deschutes only has a 2x option that disables L2 cache.

For Pentium 2/3: The Motherboard sends the 4-bit Multiplier request pattern to CPU during the first milliseconds of bootup. It is the CPU that handles it from there. It obeys when the setting is supported, otherwise it just hangs or boots at a preset locked multiplier.
After those milliseconds the 4 multiplier request connections to the CPU change from their temporary function to their normal function. Meaning you cannot send a multiplier request again with a running system, because the interface for it was closed down.

gerwin wrote on 2021-11-23, 17:09:

Forget it, 8><CUT There is no 1.5x. Not for Klamath core and not for Deschutes. 8><CUT For Pentium 2/3: The Motherboard send […]
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Forget it,
8><CUT
There is no 1.5x. Not for Klamath core and not for Deschutes.
8><CUT
For Pentium 2/3: The Motherboard sends the 4-bit Multiplier request pattern to CPU during the first milliseconds of bootup. It is the CPU that handles it from there. It obeys when the setting is supported, otherwise it just hangs or boots at a preset locked multiplier.

OK, that is clear. Thanks.
I surrender.

Just tested combination of unlocked P II 400 MHz SL2S7 and ABIT BE6-II v1.0 with 1.5x multiplier (set according to the manual) and it simply won't boot. The lowest possible is indeed 2x.

PARKE wrote on 2021-11-12, 02:04:

There are early 440BX motherboards that can go as low as 50MHz but it depends on the frequency generator that is installed. My A […]
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Joakim wrote on 2021-11-11, 20:16:

We were discussing underclocking of Pentium 2. It seems likely that Pentium 2 <333 MHz made before week 34 1998 are unlocked.
I was interested in examples of slot 1 motherboards that can set the multiplier and fsb in bios and how far you can go. Maybe even 1x50mhz is possible?

There are early 440BX motherboards that can go as low as 50MHz but it depends on the frequency generator that is installed. My ASUS P2B-S rev. 1.03 has an ICS 9150-08 that covers 50MHz through 112MHz.
I don't think that multipliers can be set to lower than 2x but I may be mistaken.
fsb3.JPGICS9150-08.pdf

I have a brace of intel SE440BX boards for which the manual reports 50MHz is supported. I have not tested it yet, nor do I have any idea about the multi.

I have found a motherboard which can underclock the CPU using the bios, tested by myself: Lucky Star 6ABX2V, it is a 440BX board, and one can use the bios to select manually the frequency.

I am using it now with an SL2HD processor, which has an unlocked multiplier.

I can select 2 x 66 in the BIOS, works perfectly, however L2 cache is disabled. At 2.5 x 66, the L2 cache is enabled.