airs wrote on 2018-05-01, 20:34:

Wanted to say thanks for sharing this mod. I performed it a few days ago and my system is running stable in Win98SE. K6-3+ 450AC […]
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Wanted to say thanks for sharing this mod. I performed it a few days ago and my system is running stable in Win98SE. K6-3+ 450ACZ @ 2.1V

So, does it only work on Asus P5A 1.06, or can it work with any Socket 7 motherboard?

Necropost, but important.

This modification is meant to address an error in the design of this board revision in particular. While it could theoretically work on another board, it would need to have had the same design error to begin with.

I did this mod to my 1.06 P5A board with a 1k resistor and it works too (with K6-III+ 400 atz). I have found the same issue with the cpu voltage at 2.0v the voltage regulator hasn't signal (0 v) but with 2.1v the system does boot up. I've compared to the rev 1.04 board and the memory performance is looks like little bit different, due to the onchip tag (or the newer northbridge revision), the read and latency is the same, but writing is slower, while copy is faster.
Anyway the other performance (like Quake timedemos, 3DMarks, Superpi) is almost the same, 1.06 board wins with few points but within the measurement error limit.
I've tried a vanilla K6-III 400 (which is in before) and the board and everything seems ok.
I didnt perform a long-term stability test (just few hours Quake1/2/3, 3 (few rounds Openarena under Linux) 3Dmark2k/2k1 loops and prime95), but it was rock stable even on overclocked (112) fsb (I've tried under Dos, Win95OSR2.1, 98SE, 2K SP4, XP SP1, Linux Mint 9 Fluxbox).

Update: I confirm that the mod isnt affecting the memory or other (cpu, graphical etc) performance i've check it with or without the mod and the results are the same. Also the normal cpus works after the mod.
I have another P5A rev 1.06 like this, but it has 1 MB onboard cache and tag chip (I've checked with wpcredit and strangely both tagchips are active), the northbridge revision is the same (G) but little bit older ('99 vs '00) , sadly this board is only stable in Dos and Win95/OSR2.X, newer op's like 98, 2000 or Xp are resetting (like someone mentioned before) if the system is idle (under Linux even during the system startup), under load (and normal cpus) it seems stable. Stability is little better if prevent irq sharing (manaully add irq in bios) and increase the pci latency timer to 64, but not solve it, so the mods are half success 1 off 2 prefectly stable.

My modded v1.06 P5A random reboots in Windows 98SE with one PSU but with another PSU perfectly stable @115FSB.

So try a different PSU.

I've tried it with multiple psus (from 250w to 560w and different vendors like FSP, Seasonic, Chieftec, and some noname (Deer, Codegen)), but it didn't matter at all, not all mobos seem to be stable with this mod, you have to try it like core unlock with cpus or pipe unlock with vgas.

Got my mobo working by disabling delayed transactions. Don't ask how it works but it's stable now.

quicknick wrote on 2020-07-02, 23:15:

Not surprising, since the VRM used cannot provide 2.0 volts (at least, not in the way Asus implemented it). Found out yesterday […]
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FesterBlatz wrote:

There's also been some "oddness" going on with Vcore jumper settings. Even though I'm using a K6-2+ with a nominal Vcore requirement of 2.0v, I've discovered that I need to set the jumper position to 2.1v to get the board to post and boot.

Stedman5040 wrote:

At 2.0v the system will not boot with a K6-2+550.

Not surprising, since the VRM used cannot provide 2.0 volts (at least, not in the way Asus implemented it). Found out yesterday while restoring the P5A v1.05 that I recently got.
Here's an excerpt from the datasheet, and it's clear that the jumper settings labeled 2.0V on the board and in the manual is giving in fact 0 volts (confirmed with a multimeter), so I guess Asus made a sloppy job with this board.
HIP6004B.jpg

In the following days I intend to ground the VID4 pin (not accesible through the jumpers) to access the 1.3-2.05V range and of course to implement the resistor mod for using the board with a 400ATZ (@500, don't need it higher). I'll update here when job done.

Is this a problem specific to the P5A and not the P5A-B? Or possibly revision-specific? (maybe voltage regulators with similar, but not identical pinouts and feature sets were used)

I'll have to go over my P5A-B to check what it uses, but the 2.0 and 2.1V settings seem to work fine, and BIOS reports 2.0V when selected.

I'm almost certain my board has an older revision of the chipset and the board level cache only supports up to 128MB with the 512kB SRAM onboard. (which also made my selection of DIMMs for overclocking or CL2 SDRAM timing attempts more limited, at least where I wanted the board level cache functional; given I have a lot of 256MB PC-133 DIMMs but not many 128MB or smaller ones)

I'm not looking at the board right now, but the machine it's in has Sandra 99 spec it as Revision 1.xx with serial number dating it to August 26, 1998 and BIOS rev 1.003 (I still haven't flashed that ... should probably dump the original BIOS first, too).

I'm not sure what revision that date would make the board, but maybe 1.03. (Anandtech reviewed a 1.03 on September 1, 1998, so that seems about right)

dj_pirtu wrote on 2021-07-11, 16:05:

Got my mobo working by disabling delayed transactions. Don't ask how it works but it's stable now.

Did you have an ISA sound card connected while also enabling Delayed Transaction? I ran into this same issue on my rev1.04 where the power would go wonky and the CPU fan would speed up and down constantly. Delayed Transaction just breaks everything on these boards.

I recently got my hands on a P5A rev1.06 (512K cache version) and I need to do the mod on it. However I am lost on the resistor to get. Assistance is greatly appreciated:

I have started a search here but don't know how to narrow it down further. Brand (which is best)? Wattage (what's the max we actually need)?
https://www.digikey.ca/en/products/filter/chi … i%2BSXJUQKDqstA

Many thanks~

I was using Gravis Ultrasound and SB AWE64...

Resistor value dont need to be exact, it's just making a "pull up" if I remember right. There's no current going through it.

Edit: read further before attempting this

I’m trying to do a more complex version of this mod

My understanding is that I can pull this setting high, or low

But I’m unclear as to which pins to use,

I understand the resistor should go on the option pin

And that I can pull that to ground or to vcc

Can someone help me out with the rest of my plan here?

At the very least I want to be able to disable the mod as I hear sometimes it makes specific cpus not work right.

Looks like the mod is to pull the WB pin AA5 high to 3.3V through a 1k resistor. If you want to do that through a jumper then I think it means soldering the resistor to pin AA5, then solder one wire to the other side of the resistor. Solder the other wire to any convenient 3.3V that's easy to get to (it may be easier to find a point on the top of the board). Then those two wires go to a jumper header. Then fit the jumper to enable the mod and remove it to disable the mod (it breaks the circuit to 3.3v, so the WB pin goes back to whatever voltage is was before the mod).

snufkin wrote on 2021-12-15, 22:40:

Looks like the mod is to pull the WB pin AA5 high to 3.3V through a 1k resistor. If you want to do that through a jumper then I think it means soldering the resistor to pin AA5, then solder one wire to the other side of the resistor. Solder the other wire to any convenient 3.3V that's easy to get to (it may be easier to find a point on the top of the board). Then those two wires go to a jumper header. Then fit the jumper to enable the mod and remove it to disable the mod (it breaks the circuit to 3.3v, so the WB pin goes back to whatever voltage is was before the mod).

Check my work here,

1k smd resistor on bottom, I had to use alternate vcc3 pin because of confusion when routing. Wires are superglued.

Checked to make sure they aren’t shorting to pads below.

Where should I attach the remaining wire for pull down?

How’s it look?

The board has the latest 1011 beta 005 bios

But refuses to work with 2+ cpus no matter what setting I select on the jumper or removed entirely.

But works fine on k6-3 and k6-2 non plus

Ideas?

Noticed psu doesn’t have -5v
Edit:
It’s working now, not sure what issue was, but all I did was set a few bios settings, plug a fan in and a diag card, nothing that I would have suspected would fix it…

Cpu posts in all three settings, pull up, pull down and open.

So good sign.

Will be a while before I can do benchmarks

Hi Sphere478,

Do you mind pointing me in the direction of the resistor I need to do the simple version of this mod?

My earlier search on digikey:
https://www.digikey.ca/en/products/filter/chi … i%2BSXJUQKDqstA

That'd be a great help so I can hopefully get this done. After also buying a soldering iron, solder, flux... oh yeah and learning how to do it in the first place. 😅;

IcySon55 wrote on 2021-12-16, 02:40:

Hi Sphere478, […]
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Hi Sphere478,

Do you mind pointing me in the direction of the resistor I need to do the simple version of this mod?

My earlier search on digikey:
https://www.digikey.ca/en/products/filter/chi … i%2BSXJUQKDqstA

That'd be a great help so I can hopefully get this done. After also buying a soldering iron, solder, flux... oh yeah and learning how to do it in the first place. 😅;

I used the same one as OP

I suggest using a jumper like I did for at the very least disabling the mod because according to some users the mod makes some other cpus not work correctly. (Don’t recall details)

I got my volt meter and found a 1k resistor on a broken motherboard I have.

That's the thing, I can only see the one that OP used visually and have no idea how to find it on digikey. I don't have extra dead boards to salvage from, nor the tools to do it.

IcySon55 wrote on 2021-12-16, 07:22:

That's the thing, I can only see the one that OP used visually and have no idea how to find it on digikey. I don't have extra dead boards to salvage from, nor the tools to do it.

Any 1k ohm resistor will do.

Type in 1k ohm smd resistor
That’s what OP and I used
I think it’s like 1/16w?

But any 1k resistor should do the trick