VOGONS


First post, by chimken

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Hello

First my relevant specs:
Motherboard: PCPartner
BXB847D

Here's the manual
CPU: Intel Celeron 300A, currently at stock 300Mhz
RAM: 2x 64mb PC100 standard

I'm trying to overclock my CPU to 450Mhz but there's no option in bios for 100Mhz FSB, the highest it goes is 83, as per screenshots below. Presets also don't offer 4.5x100. I checked with BIOS editor and the options are there, but not in the actual BIOS. Both the profile on theretroweb and the manual suggest 100Mhz is supported by the motherboard.

I suspect the voltage needs to be changed, but there's no option for that anywhere in the bios and manual doesn't help much. One section in manual that looked promising is '2. When you use 350MHz, 400MHz and 450MHz CPU, DIMM RAM must be PC100 standard' but both my dice are, at least per the stickers on them.

I tried the newest bios available for the board (2A69KV3IC) but it has the same issue. I'm over my head at this point, do you guys have any suggestions?

Reply 1 of 9, by myne

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You could try taping pin b21 and see what happens.

Pretty sure my old memory is right that that's the fsb 66/100 pin.

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Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
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Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 2 of 9, by chimken

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I saw that about on this forum but with no details. Googling brings stuff up but I wouldn't want to break anything - can you please link to a reliable source with more info on that procedure?

Reply 3 of 9, by marxveix

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myne wrote on 2025-07-18, 11:13:

You could try taping pin b21 and see what happens.

Pretty sure my old memory is right that that's the fsb 66/100 pin.

I have done that many years before with my celeron 300a, worked well @450mhz, i just used tape with clue.

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Reply 4 of 9, by myne

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Cut really thin piece of sticky tape.
Place carefully on the edge finger you've identified as b21.
Triple check you can count and didn't cover the ones next to it
Insert into socket.
Make sure it looks like it didn't slide off.
That's pretty much it.

At least 4 pins should be labelled. A1, A121, B1, b121

It's tricky to get right, but even harder to screw up so bad something dies.

I built:
Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
Dos+Windows 3.11+tcp+vbe_svga auto-install iso template
Script to backup Win9x\ME drivers from a working install
Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 5 of 9, by chimken

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Ah, so just masking the 21st pin counting from B1 on the edge connector, got it. I'll give it a shot

Reply 6 of 9, by myne

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Bingo.
Good luck!

I built:
Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
Dos+Windows 3.11+tcp+vbe_svga auto-install iso template
Script to backup Win9x\ME drivers from a working install
Re: The thing no one asked for: KICAD 440bx reference schematic

Reply 7 of 9, by Matth79

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Board / chipset appears to be 100MHz rated, even if it's the budget ZX (unless they did the dirty and put a ZX-66 on).
So if it isn't a ZX66 chipset (for which a max oc of 83 sounds feasible) then the other potential is that without detecting a 100MHz CPU, it sets straps and dividers that won't work with 100.
So it might work with the B21 hack, it might work, it might not, or if it selects 83 then that would be pretty conclusive that they downgraded the chipset
Looks like the chipset heatsink is glued, so removing it to check the model & stepping is not an option

Reply 8 of 9, by chimken

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It worked brilliantly, thank you.

If someone with the same issue stumbles upon this post, here's what I did. It's the pin marked on the screenshot. Tape was too fiddly for me so I just painted it over with nail polish. If you 'go over the lines' it's easy to delicately scrape the polish off of the neighboring pins before it completely solidifies.

Once connection was blocked on B21 the PC immediately recognized the CPU as 450MHZ (100x4.5)

Reply 9 of 9, by myne

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Nice one

I built:
Convert old ASUS ASC boardviews to KICAD PCB!
Re: A comprehensive guide to install and play MechWarrior 2 on new versions on Windows.
Dos+Windows 3.11+tcp+vbe_svga auto-install iso template
Script to backup Win9x\ME drivers from a working install
Re: The thing no one asked for: KICAD 440bx reference schematic