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Tualatin slotket mod on Intel BX chipset (rom.by edition)

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First post, by vutt

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Decided to dive into wonderful world of PIII hardware modding. I understood back in days rom.by was among other things rather popular modding site in post SU area with guides and forum.
I can read Russian. So why not challenge myself. It took me some time to hunt down rather specific generic 370CPU rev 1.0 slotket. No voltage regulator onboard.
I have Asus P3B-F rev 1.04 so it supports lower Tualatin voltages. I'm using [urlhttps://www.vogons.org/viewtopic.php?f=46&t=69345]THIS[/url] BIOS mod. I followed rom.by guide to the letter here: https://www.rom.by/articles/S370/index.htm.
I have to admit it was rather fiddly undertaking to push socket pins and drill holes to PCB. I did not want to abuse my CPU. I managed to get it working right away with one scare...

... per guide for voltage control short VSS, VID2 and VID25mV. This resulted 1.65V by bios reading. Ouch. Quick googling hinted that I might need only VSS and VID25mV connected.
So what is this? Old exSU area PC enthusiasts like living on the edge and what can be overclocked/overvolted should be overvolted by default? 😉
Also G35 and G37 (VTT pins shorting is rather unique, no other Tualatin mod guides suggest that)

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Reply 1 of 6, by PARKE

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The G35 & G37 mod is also listed here:
https://www.oocities.org/_lunchbox/generic_slotket_mod.html

PS
And according to this link the 1.65v result depends on the cpu stepping:
https://www.oocities.org/_lunchbox/vid_mod.html
ooooooooooooooooooooooooo
If your CPU has default voltage of 1.45 or 1.475, then bridge AM34, AM36, AL35, AK36 on the motherboard, slotket or CPU to give you 1.45v. If CPU default is 1.475 follow the VID mod for 1.45v since most old VRMs can only adjust by +/-0.05.
The latest stepping CPUs, SL68P, runs at 1.5v default. If you were to apply the above VID mod to a SL68P, you would obtain 1.65v for a default voltage. The mod bridges VID0 and VID1 while the CPU has VID2 bridged internally. Add those together when you install the CPU, and you end up with VID1+2+3=1.65v.
ooooooooooooooooooooooooo

Reply 3 of 6, by vutt

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Thanks @BARKE!

This makes sense now. So it's initial voltage. So from cold boot with only VID25mV connected I indeed get 1.3V as per BIOS sensor. However have selected manual voltage option as 1.45 (I have 1.45 CPU) so BIOS seems to apply it before booting to Op.system. In Windows sensor is reporting correct 1.44V. And if I then restart BIOS HW monitor keeps showing correct 1.44V. To be sure checked with multimeter and indeed CPU VCC pin reading is in sync with Asus VCC sensor.
This is my first Tualatin experience. Back in days I jumped from Coppermine to Athlon. It's amazing that Tualatin can actually boot with 1.3V.

Also thank you for that generic slotket link - now I know jumper J4 meaning. Mine was hard wired out of the box 1-2 (BSEL-A14). However all Tualatin mods examples with this Slotket I have found had jumper in 2-3 position BSEL to GND. So I resoldered JP4 in the same way.

Reply 5 of 6, by vutt

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Thanks.
Strangely enough my "undocumented" jp1 1-2 & jp4 2-3 works for 133fsb. I also tested 66fsb - works as well. However when I tried 140fsb it did not post. I'm now tempted to solder real jumpers on my board and play around with combinations...

Edit: ended up soldering jumper pins for jp4 and left it on 1-2 - seems to be working just fine by choosing from bios 133/33 manual speed. For BX chipset it already means decent FSB and AGP overclock.

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