sirlemonhead wrote:

Hey, […]
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Hey,

Managed to pick up this Pentium 1 machine from work that was due for the bin. Turns out to be a Pentium 75mhz with 8 megs of a ram and a S3 trio card.

Fairly basic but what's interesting to me is it's actually the first proper retro OEM machine that doesn't have a locked down motherboard - it has a BIOS full of options and jumpers to set FSB, cpu voltage and... multiplier..I think?

I'm basically replacing the 75mhz CPU

with this 133mhz chip

But I'm not sure how to set the multiplier on the board. I've changed the FSB from 50 to 66 which has got the cpu running at 100mhz but it's obviously still running at a multiplier of 1.5 - I need to set this to 2.0

I can't figure out how to set this.. could someone help? Here's two photos of what I *think* it is I need to change, but I'm clueless on how to set the jumpers. The board seems to be an Intel 82430FX TRITON

I think you need to set the "CPU INT SPEED" to "1/2".

Jumper on JP10, no jumper on JP5. EDIT you need to add a jumper as JP5 is already empty.

thanks 😀 Any idea which one is JP5? I'm a little confused by the labelling...

sirlemonhead wrote:

thanks 😀 Any idea which one is JP5? I'm a little confused by the labelling...

I edited my message but you were too fast. 😀

My first edit was not the best advice though. You need to find a spare jumper as JP5 is already empty. I edited my post again.

I agree that the labeling is very confusing.

Note that the row of jumpers on the right are all JP28 and sets the V-Core eventhough it looks like the first jumper is JP25 and the second JP5. This is very bad design eventhough this motherboard cant set any voltages that are dangerous for the CPU.

This is how it probably is.

But this says that your board is jumperd for 2.5x at the moment which seems strange. Perhaps they have for some reason used 0 to equal "jumper" and 1 to equal "not a jumper" which would make this setting 1.5x and a jumper on JP5 will make it 2x with JP10 still empty. I would try this!

Jumpering JP-5 has the Bios reporting a 133mhz CPU so that's looking good. Thanks! 😀

How does the 2/3 and 1/2 values relate to the multiplier?

sirlemonhead wrote:

Jumpering JP-5 has the Bios reporting a 133mhz CPU so that's looking good. Thanks! 😀

How does the 2/3 and 1/2 values relate to the multiplier?

2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB

1/2 = FSB "1" CPU "2" so the CPU = 2X FSB

2/5 = FSB "2" CPU "5" so the CPU = 2.5X FSB

1/3 = FSB "1" CPU "3" so the CPU = 3X FSB

Totally not logical 😀

Skyscraper wrote:

2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB […]
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sirlemonhead wrote:

Jumpering JP-5 has the Bios reporting a 133mhz CPU so that's looking good. Thanks! 😀

How does the 2/3 and 1/2 values relate to the multiplier?

2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB

1/2 = FSB "1" CPU "2" so the CPU = 2X FSB

2/5 = FSB "2" CPU "5" so the CPU = 2.5X FSB

1/3 = FSB "1" CPU "3" so the CPU = 3X FSB

Totally not logical 😀

Wow, this is really bad 🤣 . I thought it was merely referencing the FSB as well. OP, have fun with that Pentium 133! What do you plan on playing?

I have no idea what to do with it yet to be honest! 😁 I've only got as far as putting Dos 6.0 and Win 3.1 on it. I'm not bothered with Windows 95 or later on it as I have that covered by other machines.

I already have a Gateway 2000 P75mhz (I don't want to upgrade the cpu in that) so this might be my tinkering machine - can try out the various bits of old ram and ISA cards I find in it to see if they work 😀

If I ever see a decent replacement case, I think i'd definitely change it... the power button is just awful 😀 I mostly just pull the power lead out of the back to get it to power off but that's probably not too good for it 😀

Skyscraper wrote:

2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB […]
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2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB

1/2 = FSB "1" CPU "2" so the CPU = 2X FSB

2/5 = FSB "2" CPU "5" so the CPU = 2.5X FSB

1/3 = FSB "1" CPU "3" so the CPU = 3X FSB

Totally not logical 😀

They just show the divider instead of the usual multiplier.
3/2 = 1.5
2/1 = 2.0
5/2 = 2.5
3/1 = 3.0

Consistent, arguably logical, but not using common conventions.

idspispopd wrote:

They just show the divider instead of the usual multiplier. 3/2 = 1.5 2/1 = 2.0 5/2 = 2.5 3/1 = 3.0 […]
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Skyscraper wrote:

2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB […]
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2/3 is FSB "2" CPU "3" so the CPU = 1.5X FSB

1/2 = FSB "1" CPU "2" so the CPU = 2X FSB

2/5 = FSB "2" CPU "5" so the CPU = 2.5X FSB

1/3 = FSB "1" CPU "3" so the CPU = 3X FSB

Totally not logical 😀

They just show the divider instead of the usual multiplier.
3/2 = 1.5
2/1 = 2.0
5/2 = 2.5
3/1 = 3.0

Consistent, arguably logical, but not using common conventions.

The logic is in the eye of the beholder 😜. ("1/3") x CPU = FSB which is totally backwards as its the mutiplier you are setting.

The way I wrote it while really drunk at least seems a little bit logical even when sober.

Ugh, I have a board with fractional multipliers in the table like that. Royally pisses me off. Since when do computer guys know how to do fractions? I haven't used them since I was in primary school and even then they seemed archaic and I used to get into trouble for using floating points on my maths papers.

My board is from a Tiny system... They were never very good so the silly writing seems fitting.

Am I weird for liking fractions? My professors usually just fired up their calculators and used the decimal numbers, but I like postponing that as much as possible and use fractions until later stages of the calculations, as I feel that reduces rounding errors that propagate the more you use the rounded numbers.