If you can keep the CPU cool enough, it shouldn't be a big problem, but overclocking by that much long term can cause the chip to degrade faster.

I believe its not entirely stable after a little warm up period. This might not even be a question, I guess I'll have to find a working 120.

Chances are that the real P120, that has been manufactured using more efficient process will run cooler and be more stable that the overclocked P90 part.

Those CPUs cost peanuts so I'd personally use the real thing just for good feeling.

If the CPU does not get overly hot and is running at stock voltage then it should be fine, Pentiums are known to be good overclockers, though you may want to perform additional stability tests.

Regarding the 120MHz CPU, maybe it's one of those that requires additional voltage to run properly? What are the 3 letters on the back of the chip? It can be something like SSS, VMU or other combinations. The first of those 3 letters indicates whether you should use STD (S) or VRE (V) voltage, and there should be jumpers on the mobo for setting that in addition to the bus frequency and multiplier.

It is VMU and the manual says:

Advanced/ZP Technical Product Summary • Page 16PROCESSOR VOLTAGE REGULATION - SWITCH 2Sets the output of the on-board voltage regulator. The switch settings are OFF = VR, and ON = VRE. The VR voltagespecification requires a voltage range of 3.3-3.465 Volts DC, while the VRE specification requires a voltage range of 3.45-3.6V. Pentium processors currently available that do not require the VRE voltage specification should use the VR setting.When upgrading your CPU be sure to consult the documentation for the processor voltage requirements before setting thisswitch, as an incorrect setting may damage the processor. The default position is with the switch set for VR (off).

So I need to check and see if switch 2 is set to on as you specify.

Got the same results as the other voltage setting, maybe I damaged the chip by trying it with the wrong setting to begin with.

I'll look for another 120 chip.

Sorry for the link to ebay, but what would the pictured chip be set to voltage wise:

https://www.ebay.com/itm/Intel-Pentium-A80502 … TgAAOSwSYdbxm59

Edit I ended up picking up a couple chips that were SSS, so those should work without changing the voltage setting from my p90.

It's not possible to damage a 3.3-3.465V chip at 3.45-3.6V, you should ask for a refund as you got a defective CPU.

Your P90 could probably handle 100MHz very well, and the performance would't be too far off the P120 due to the higher FSB.

Do you think I could run a Pentium 150 at 132Mhz by setting the FSB to 66Mhz and the multiplier to 2 even though the motherboard doesn't specifically specify that CPU? Would I at least be able to set the 150 CPU to run at 120 since the motherboard does support that?

Here is my motherboards manual:

http://pdfstream.manualsonline.com/1/1108b1a2 … 8973a837ed0.pdf

Im wondering if setting the FSB to 66 will throw off the ISA bus speed too much...I guess I'd have to experiment, I just dont want to kill the board.

Maybe something like this could work?

https://www.ebay.com/itm/270818967936

Don't take my word for it, perhaps someone else can confirm.

EDIT: seems like you edited your post, but I'll leave the link there in case it's useful.

TheMobRules wrote on 2020-12-01, 05:28:

Maybe something like this could work?

https://www.ebay.com/itm/270818967936

Don't take my word for it, perhaps someone else can confirm.

Thanks that does look like the proper cable! Sorry for the edit, I've been shopping in real time, didn't mean to confuse.

Get a Pentium 166 PGA. like this:

https://www.cpu-world.com/sspec/SY/SY037.html

I have one and I can set it to any existing pentium classic frequency, both multiplier and bus without the slightest problem. Probably its production process is the last of the pentium1 series given the typical package of the pentiumMMX and holds 200Mhz perfectly fresh. I use it to see how the software works at various frequencies from 75 to 200mhz

Pentium 120 came in two variants, the "classic" P54C and the die-shrunk P54CQS. It may be your board doesn't support the die-shrunk versions, since it also doesn't mention 133, which is P54CS.

According to my notes, the P54C versions of Pentium 120 are s-specs and Q-specs: Q0707, Q0708, Q0711, Q0372, SK086, SX994, Q0785, SY033.
Where as the P54CQS are s-specs and Q-specs: Q0776, SK110, SY062

The following s-specs and Q-specs, I am not sure whether are P54C or P54CQS. Q031, SK084, SY008

What s-spec or q-spec is your P120?

Shagittarius wrote on 2020-12-01, 05:07:

Do you think I could run a Pentium 150 at 132Mhz by setting the FSB to 66Mhz and the multiplier to 2 even though the motherboard doesn't specifically specify that CPU? Would I at least be able to set the 150 CPU to run at 120 since the motherboard does support that?

Here is my motherboards manual:

http://pdfstream.manualsonline.com/1/1108b1a2 … 8973a837ed0.pdf

With this sort of stuff, always consider that manuals are written at time of release and rarely if ever updated. Despite some internal changes (die shrink, reorganized components), the P54C (Pentium 75-100), P54CQS (Pentium 120) and P54CS (Pentium 133-200) present exactly the same interface to the outside world. Your board may lack the (BF1) jumper required to set 2.5x/3x multiplier, but if you put any Pentium CPU in this board jumpered for 120MHz, it will run it at 120MHz, and any Pentium CPU rated 120MHz or higher will be able to handle that if not dead.

Im wondering if setting the FSB to 66 will throw off the ISA bus speed too much...I guess I'd have to experiment, I just dont want to kill the board.

Eh? Take a look at page 16 of the manual. Generally you'll want to run ISA at 8.33MHz. You can only hit that with 50 or 66MHz FSB, not with 60MHz. With SW1 on, you'll always stay at or below that value. However as the manual states, it's not the board that will have trouble with higher speeds, it's older ISA cards. In any event, you're not going to kill the board with officially supported settings (if the board can't handle those it's already borked).

I'd recommend reading up on the kinds of things that can kill old hardware, as you seem to be very cautious towards the wrong things. I'd recommend a focus on proper ESD practice, making sure your PSU is good and testing new components in a different (more expendable) system, as those are the big reasons why (old) hardware dies, not using supported settings of a very conservative board from a very conservative vendor.

Surprised there even was a P54C version of the P120. I remember when the P120 announced the 0.35 μm process that made it possible was a major part of the press coverage. Despite using the same die area as P54C (and thus the P54CQS). I'd assume they later switched to P54CS and not the other way around.

if you put any Pentium CPU in this board jumpered for 120MHz, it will run it at 120MHz, and any Pentium CPU rated 120MHz or higher will be able to handle that if not dead.

This is what I figured just thought I'd ask before I did so...

Eh? Take a look at page 16 of the manual. Generally you'll want to run ISA at 8.33MHz. You can only hit that with 50 or 66MHz FSB, not with 60MHz. With SW1 on, you'll always stay at or below that value. However as the manual states, it's not the board that will have trouble with higher speeds, it's older ISA cards. In any event, you're not going to kill the board with officially supported settings (if the board can't handle those it's already borked).

Thanks I was a little confused since that graph goes by processor speed and not FSB speed, I was unsure how an FSB speed of 66 would have effected that.

This brings up another question though, If I've only got a Sound Blaster Pro 2.0, a SCSI controller card, and a Roland MPU-401 interface in the ISA slots what would be the benefit of running the ISA bus at a higher speed? Maybe faster throughput for the SCSI HDs? It seems likely to cause problems for the Soundblaster, and even if not, what good would that do?

I'd recommend reading up on the kinds of things that can kill old hardware, as you seem to be very cautious towards the wrong things. I'd recommend a focus on proper ESD practice, making sure your PSU is good and testing new components in a different (more expendable) system, as those are the big reasons why (old) hardware dies, not using supported settings of a very conservative board from a very conservative vendor.

I'm not really that afraid, I dont have the desire to get any more hardware to test with which is why I just wanted to ask if I might run into any board destroying problems...thanks for the advice.

H3nrik V! wrote on 2020-12-01, 08:13:

What s-spec or q-spec is your P120?

My 120 that seems to be dead is the SX994

Shagittarius wrote on 2020-11-30, 22:51:

Got the same results as the other voltage setting, maybe I damaged the chip by trying it with the wrong setting to begin with. […]
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Got the same results as the other voltage setting, maybe I damaged the chip by trying it with the wrong setting to begin with.

I'll look for another 120 chip.

Sorry for the link to ebay, but what would the pictured chip be set to voltage wise:

https://www.ebay.com/itm/Intel-Pentium-A80502 … TgAAOSwSYdbxm59

Edit I ended up picking up a couple chips that were SSS, so those should work without changing the voltage setting from my p90.

I think VRE was only used on very few P5 CPUs but I can't find a definitive list. *most* socket 7 pentium (non-mmx) should use 3.3 (aka STD) core voltage

As a general rule, running a CPU (or anything I guess) at a higher than rated voltage means more heat which means shorter potential lifespan.

Success! Thanks everyone who contributed here, I got a P-150 running at 133 on this board today and, after about an hour of gaming / benchmarking, it seems to be stable.

So the conclusion must be that the 120 was defective?