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Which Pentium IIs can be underclocked?

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Reply 180 of 217, by archsan

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AdamP wrote:
http://i825.photobucket.com/albums/zz180/adamplenty/P1010007.jpg […]
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Tetrium wrote:
AdamP wrote:

Well, I can't try the SL2KA because I think the heatsink's on the wrong way around so I can't plug the CPU in and I can't remove it..

Sounds strange...
Could you take a pic please?

P1010007.jpg

Definitely looks like it's on the wrong way around to me.
[/img]

Maybe it's meant to be snapped in two like Kit-Kat?

😜 jk -- you must detach it then -- is there any screwhole or some kind of a clip in the back?

if not i'm afraid you have to snap it open... maybe wrap-in-a-plastic-bag-and-put-it-in-the-freezer trick?

Reply 181 of 217, by ux-3

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Sure you can remove it. It is attached by 4 Screws in the side of the cooler. These screws may look like small bolts, but they have a telling hexagonal core, which fits an inbus key. I was fooled first and broke open a locked CPUs case till I found out.

If you are lucky, you can even turn it upside down.

Retro PC warning: The things you own end up owning you.

Reply 182 of 217, by AdamP

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I've already removed the screws. But I just can't get the heatsink to budge. All I've managed to do so far is open one side of the case.

Not sure if this'll help but this is what it looks like:

P1010010-1.jpg

Reply 183 of 217, by Tetrium

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My guess is someone simply mounted the cooler on backwards.

Could you post a pic of what the front of the CPU now looks like?
I've removed coolers from these processors before but often those oem coolers are a pain to remove without breaking anything.

Reply 185 of 217, by AdamP

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Are these what you want?:

P1010017.jpg

P1010015.jpg

Do different PIIs have different heatsink locking mechanisms? I removed the heatsink on my SL2U6 without much difficulty, but it wouldn't fit properly on my SL2HE so I had to put it back.

Reply 186 of 217, by Tetrium

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AdamP wrote:

Do different PIIs have different heatsink locking mechanisms?

Yup, theres the earlier fully enclosed P2's and the 'half open' model that was also used on the slot 1 P3's.

Have you succeeded in removing that heatsink now btw?

Reply 187 of 217, by Mau1wurf1977

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Sorry to jump in, just a quick question...

What CPU equivalent can emulate with a Pentium 2? E.g. enabling caches...

Anyone disabled the caches on a PII? Will it be even slower than P IIIs or are they quite different...

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Reply 189 of 217, by AdamP

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ux-3 wrote:

Take a screwdriver and pop the cooler off

That worked! 😀 Thanks

But I couldn't fit it on the right way around. I also tried the heatsink from my SL2U6, which also didn't fit properly. I ended up using the heatsink from my SL2S5. My guess is that the heatsink was meant for another PII.

The CPU isn't locked 😀 although I had to up it to 200mhz to keep the L2 cache. Why doesn't the L2 cache work at 166mhz when it did for the SL2HE? (My wild guess is that the multiplier has to be higher than half the default)

Is what this says true? If so, it seems that it was produced week 23 1998 (and my SL2S5 was produced week 42 1998 and my SL2HE was produced week 24 1998).

Thanks for your help

Reply 190 of 217, by Mau1wurf1977

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Quick question, I would love to know what applications do you under clock these cpus for?

I got the impression that they are to fast to "turn into" a 386 and when disabling L1 cache you end up with a XT machine?

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Reply 191 of 217, by ux-3

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Mau1wurf1977 wrote:

Quick question, I would love to know what applications do you under clock these cpus for?

I got the impression that they are to fast to "turn into" a 386 and when disabling L1 cache you end up with a XT machine?

As I told you before, a number of Windows games are speed sensitive:
Magic the Gathering's Shandalar comes to mind immediately.

As I have also answered you before, the 486 region is a blindspot you won't be able to hit with a Slot1 CPU in hardware. That is why I have adopted a real 486.

There is however a utility that will help you. It is called "Throttle". I have only used it shortly, until I discovered that joysticks don't work well with it. If your game needs no joystick, this is an option.

If you only disable L1 cache but keep the clock up at about 400 MHz, you are getting a 286 for many purposes.

Reply 192 of 217, by Mau1wurf1977

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No worries thanks for the info! I'm in "386 mode" so I might have missed your other comments regarding pentium and 486...

Yes I saw your post about throttle and joustick drift. Definitly an issue for me as love Wing Commander!

Cheers for the input!

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Reply 194 of 217, by The Serpent Rider

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What matters is production week, not stepping. Only CPUs before August 1998 had unlocked multiplier.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 195 of 217, by gerwin

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W.x. wrote on 2021-03-04, 11:58:

Ok, I've got today SL2SP Deschutes 333 (stepping dA1), I though it is one of the earliest steppings, so it will be unlocked. No luck. 🙁 It is locked! So only dA0 is safe.

You also have the Date Code?

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Reply 197 of 217, by H3nrik V!

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https://www.cpu-world.com/forum/viewtopic.php … ocked+deschutes

Seems to be date rather than stepping, yes.

[Edit]: Or maybe the span in production dates is due to different phasing in of new stepping in different production plants ..

Please use the "quote" option if asking questions to what I write - it will really up the chances of me noticing 😀

Reply 198 of 217, by The Serpent Rider

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You probably may have luck within 1-2 weeks depending on CPU factory. But I have no idea which factory implemented multiplier lock first.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 199 of 217, by bmwsvsu

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Just thought I'd share, I was playing around today with a motherboard from an old Compaq Deskpro along with a P2 Klamath 300/66 processor.

The board has a 6-switch dipswitch for setting the multiplier as well as a few other things. Switches 2 through 4 control the multiplier.

As documented in the manual for this computer, the clock settings are as follows:

100   	3.0x	200
110 3.5x 233
001 4.0x 266
011 4.5x 300
101 5.0x 333

Note that there are 8 possible positions and thus 3 that are not documented as follows:
000
010
111

So I tested the first 2 and found that:

000 results in a 2.0x multiplier and a 133 MHZ speed (also disables the L2 cache)
010 results in a 2.5x multiplier and a 166 MHZ speed (L2 cache remains enabled)

...at least as reported by the BIOS. Now I haven't installed an OS yet for testing stability at these lower settings, but it does at least appear that this can be clocked all the way down to 133 MHZ just via mobo switch settings.

I'm not brave enough to test 111 - I suspect it could possibly be a 5.5x multiplier and I don't want to overheat my CPU.