Help setting up a new processor on an old IBM Aptiva 2134-440 \ VOGONS

Help setting up a new processor on an old IBM Aptiva 2134-440

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First post, by DoutorHouse

Posted on 2020-06-18, 01:11

DoutorHouse Offline

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Been restoring/reassembling an old IBM Aptiva 2134-440 I bought second-hand and I could really use the help of the experts here as i have no clue about what jumpers setting i should change and i don't wanna mess up the motherboard!

My computer has a Pentium 133Mhz processor and I'm gonna change it to a 166MHz or 200MHz one (when i actually find one). Problem is i have no clue as to what jumper settings to change. I got a copy of the technical manual but the information didn't help me much. I know the J35 jumper is already set for the correct CPU Input Clock Speed, so that's pretty straightforward (66 MHz for Pentiums 100/133/166/200, 60MHz for Pentiums 120/150 and it can also use 50 and 55mhz for other processors, but i have no idea of what kind).

The motherboard supports 100/120/133/150/166/200MHz pentiums. Manual is here:
http://ps-2.kev009.com/pccbbs/aptiva/94h5153.pdf

Now, there's also two other jumpers, marked as JP10 and JP11 to change the External/Internal Clock Speed Ratio.

These have four different possible positions and i have no idea how i should change them accordingly to other processors speeds. I looked for some more info on the internet and managed to find this but i'm still confused about the info on CPU multiplier selection (end of page):

https://stason.org/TULARC/pc/motherboards/I/I … 4-2176-A-1.html

Apparently, there's two different settings for 60mhz, one for 50mhz and one for 66mhz. Manual also mentions 55mhz but it's not listed here.

Someone would be so kind as to tell me which setting i should use for the six different processors (so I might consider downgrading it or upgrading it)? Thank you so much for any help on this!

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Reply 1 of 2, by rmay635703

Posted on 2020-06-18, 03:48

rmay635703 Offline

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That has gotta be the dumbest way I’ve seen a clock multiplier described

Anyway no worries if you find a Pentium classic 166mhz just set for 2/5 which is a 2.5x multiplier

On Pentiums of that vintage I have never seen real damage from setting the multiplier wrong, maybe no post if you overclock too much.

That said if your 133 isn’t locked can’t hurt to test a small overclock, 166 isn’t too far out of the question

Good luck

Reply 2 of 2, by DoutorHouse

Posted on 2020-06-18, 10:09

DoutorHouse Offline

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rmay635703 wrote on 2020-06-18, 03:48:
That has gotta be the dumbest way I’ve seen a clock multiplier described […]
Show full quote

That has gotta be the dumbest way I’ve seen a clock multiplier described

Anyway no worries if you find a Pentium classic 166mhz just set for 2/5 which is a 2.5x multiplier

On Pentiums of that vintage I have never seen real damage from setting the multiplier wrong, maybe no post if you overclock too much.

That said if your 133 isn’t locked can’t hurt to test a small overclock, 166 isn’t too far out of the question

Good luck

eheh, thanks for replying!!! Yeah, i checked on wikipedia and those multipliers seemed odd but I managed to figure this out, thanks to your help!

I went and compared the info on some other IBM motherboards from around the same time and now it all makes sense. Correct me if I'm wrong:

On this particular manual, one has to multiply the Pentium FSB by the second given number and then divide the result by the first given number, for instance the 1/2 setting for my Pentium 133MHz means 66.6MHz x 2 = 133/1=133MHz.

For a Pentium 100MHz, the 2/3 setting would have to be used, meaning 66.6MHz x 3 = 200MHz/2=100MHz

Other manuals present this same type of settings but using inverted numbers for the multipliers and divisors.

Just in case someone else needs this, I made a table summarizing the possible jumper settings for this particular IBM Aptiva 2134 model using just the six different Intel processors mentioned on the manual.

More info here:
http://ps-2.kev009.com/eprmhtml/eprm/f284.htm

http://ps-2.kev009.com/eprmhtml/eprma/f658.htm

http://ps-2.kev009.com/eprmhtml/eprm/f298.htm

Thanks again for your help!