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Small question - can I set a Pentium 200 MMX to 233 MHz with 1.5x multiplier?

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Peter z80.eu

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I own a working VXPro+ (VIA Apollo VPX) based Pentium (Socket 7 & Super Socket 7) mainboard, a Pentium 200 MMX is plugged in and works well.
Is it possible to "overclock" a Pentium 200 MMX CPU to 233 MHz, e.g. just by using a multiplier of 1.5x (instead of 3x for 200 Mhz) ?
A small cooler is mounted also, so heat should not be the problem. I am not sure about the usage of the 1.5x multiplier instead of having a multiplier setting of "3.5x" (not there), it is not mentioned by the mainboard manual.
Is it a usual setting for 233MHz to use the 1.5x multiplier?

Edited later: Yes, I ignored the last pages of the manual, 1.5x is usual. Will try it.
 
From what I know, no Socket 5/7 CPU from Intel allowed overclocking by using a different multiplier. They will fall back to a slower speed when trying. You need to raise the FSB instead. Intel started doing that back when many shady PC makers sold overclocked Pentium 75 CPUs as Pentium 90. Intel kept that restriction well into the Slot 1 era extending it even to the FSB.
 
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Timo W. said:
From what I know, no Socket 5/7 CPU from Intel allowed overclocking by using a different multiplier. They will fall back to a slower speed when trying. You need to raise the FSB instead. Intel started doing that back when many shady PC makers sold overclocked Pentium 75 CPUs as Pentium 90. Intel kept that restriction well into the Slot 1 era extending it even to the FSB.
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That's not correct. Every socket 7 Intel processor I've seen can have the multiplier changed. The multiplier locks didn't come around until the Pentium II

To the OP: yes you can
 
FWIW, it might depend on the chip revision. There's a vogons thread where someone claims their 200MMX actually had a 1.5x multiplier when set for that instead of 3.5x, but that conflicts with the general line that Pentium MMX multiplier choices went from 2x to 3.5x. Maybe they were confused and actually had a 200Mhz Pentium Classic.
 
Earlier Socket 5 and non-MMX Socket 7 Pentiums could usually be multiplier overclocked, but not the Pentium MMX. Every 200 and 233 MHz Pentium MMX I've ever had would refuse to boot if the multipliers were set incorrectly.

You could FSB overclock them a little bit to 75 MHz, but I've never had luck pushing them farther than that.
 
From what I remember, AMD modified the look up table inside the K6-II CPU's (K6-III & K6-II+/K6-III+) to allow the 1.5x multiplier to equal 6x. This was done, IIRC, because many mobo's didn't allow a 6x multipler switch setting. I don't recall Intel modifying the Pentium MMX CPU's to allow 6X. However, if the motherboard had manually set multipliers you could always try to overclock any Intel CPU by kicking the multiplier up a notch and testing it for function. Perhaps with some Intel CPU's that were marked as slower speed than actual limits, mostly for marketing purposes, and due to improved yields of chips capable of higher speeds you could overclock some Intel CPU's quite a bit. Not something that all Intel CPU's could handle without errors.
 
I was always able to OC my Am5x86-P75/AMD-X5-133ADW to 150Mhz by way of mobo jumper settings and stability was never an issue. Not all chips will OC and mine may be the luck of the draw.
 
Agent Orange said:
I was always able to OC my Am5x86-P75/AMD-X5-133ADW to 150Mhz by way of mobo jumper settings and stability was never an issue. Not all chips will OC and mine may be the luck of the draw.
Click to expand...
It is an AMD cpu not a Pentium 1-MMX cpu for starters.... Which is what the OP is reffering to..
 
Eudimorphodon said:
FWIW, it might depend on the chip revision. There's a vogons thread where someone claims their 200MMX actually had a 1.5x multiplier when set for that instead of 3.5x, but that conflicts with the general line that Pentium MMX multiplier choices went from 2x to 3.5x. Maybe they were confused and actually had a 200Mhz Pentium Classic.
Click to expand...

There is a thread where “someone” is testing a scrappers lot of many PMMX chips.

Pentium MMX Multipliers \ VOGONS

www.vogons.org www.vogons.org

It is common for PMMX chips to be missing a particular multiplier setting but not fully locked.
I encountered this on an old p133 that had 2 and 3x multipliers but no 2.5

From the horses mouth
AKA someone who worked on PMMX chips and Intels fab is that the available multipliers for a given revision and clock rating varied day to day batch to batch.

Meaning that targeting a particular revision of Pentium 200mmx is not enough to guarantee it has all open multipliers .

Early p200mmx would lack 3.5 because 233’s weren’t being manufactured
Later p200mmx may have 3.5 but when they did it was usually because they were a 233 that failed tests and got binned down.
From testing many chips, most 200mmx chips were meh overclockers compared to the 233 brothers , even if they had a 3.5 multiplier you usually really had to crank voltage to get them running stable at 233 or higher. I can’t say I’ve ever gotten past 250mhz on a p200mmx. P233mmxs are usually much much better examples
 
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I ended with using a real Pentium 233 MMX but I have still issues with the recognition of the correct multiplier setting.
I guess this is related with the used mainboard (it is a Matsonic MS-5120 aka PC-CHIPS PC537DMA) and the BIOS from 1998, I have to switch it on and off more than twice before it recognizes 3.5x instead of 2.5x (not sure why 2.5x and showing up 166 MHz instead of 233 MHz). It should not be related with the CMOS RAM backup battery, because the detection is made every time you switch the PC on, the type of the CPU is not stored in CMOS RAM.
 
This used to be an issue on old motherboards that would float multipliers instead of the low/hi ground scenario the chip expects
 
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