squiggly wrote:

Will this work with other CPUs? Like if I dropped a Pentium 100 in there what would happen?

I'm also curious about this.

Overall, this sounds like good news. I'm waiting for you all to determine if there are any caveats.

Did you try CPU-Z-v1.57 for Win98? This is what I use on my older systems. If you can't find it, let me know and I will read the readmes to ensure it is freely distributable.

Unfortunately I haven't had much time mess with this lately, but I do seem to be struggling with a stability issue since the mod.

I can let quake 2 run for hours without a hitch, but as soon as I start navigating around Windows 98 the machine will just randomly reboot. Never a blue screen or lockup, it simply acts like someone pressed the reset button. I don't know if it's related to the mod, or if there's some other issue at play. I sort of doubt it's the mod because the problem seems to occur more often once the system has been on a while...

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. And the hardware monitoring menu in the BIOS shows 2.0 volts. If I set the voltage to 2.2 volts, the monitoring shows 2.1 and the system becomes barely stable enough to even browse around Windows. I suspect either the power supply I'm testing with to be at fault, or perhaps some caps in CPU VRM section of the motherboard are allowing too much ripple. They look OK and are a mix of Rubicon and Sanyo but you never know. When I received the board the area surrounding the CPU socket was caked with dust from the CPU fan, so I suspect it's got tons of hours on it...

Once I have some free time I'll dig into this a little deeper, because as long as the VRM behaves strangely it's impossible to know for sure if the mod is responsible for any stability issues or not.

Do you have a non-plus AMD K6 2 or 3 chip which runs at about the same current load to compare stability with?

Yep I have a regular K6-2/500 I could try. In fact, being of the larger 0.25 µm process it should draw even more current than the K6-2+.

When I get some time I'll drag a scope over and do some poking around to verify the VRM circuit is working properly with either CPU as a load.

I did the same mod to my 1.06 board with a 1k resistor.

I have found the same issue with regards to the voltage. At 2.0v the system will not boot with a K6-2+550. At 2.1v the system does boot up. Have also found that the memory performance is still not giving the same figures as the 1.04 board using the same bios settings. Got to say though the memory performance as per Everest Home 2.20 is much improved over not having the mod. Tried a vanilla K6-III 400AHX in the board and everything fires up OK at 2.2v. I have not given up on it yet, but there are still issues with this vesion ogf the board regards K6+ cpus

Stedman

Are the memory throughput results of the non-plus, K6-III 400AHX, the same with and without the resistor mod on your v1.06 board? Apparently the non-plus chips work fine on v1.06 and later boards, so just wanted to ensure that there was no loss of performance or stability.

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

Nice! Looks like we can snatch P5A boards on higher revisions now 😀.

Why are some people reporting issues and some not? Is the mod being done the same way? I have 2 of these mobos which I was planning on throwing of a cliff once I found out they couldn't handle K6+s.

airs: Do benchmarks confirm that your + chip works the same as your non-plus chip at the same freq, e.g. compare a K6-III-450 to a K6-III+ 450?

feipoa wrote:

airs: Do benchmarks confirm that your + chip works the same as your non-plus chip at the same freq, e.g. compare a K6-III-450 to a K6-III+ 450?

Unfortunately I only have a K6-2 500 and K6-2 300 to test with. Would that be sufficient?

You can compare benchmarks of the modified board before the mod with K6-III-non-plus and after the mod with K6-III+. Or, you can get some idea for proper performance by using a second, but similar, motherboard which is known to work properly with the K6-III or K6-III+

feipoa wrote:

You can compare benchmarks of the modified board before the mod with K6-III-non-plus and after the mod with K6-III+. Or, you can get some idea for proper performance by using a second, but similar, motherboard which is known to work properly with the K6-III or K6-III+

Sounds good - I also have a Epox MVP3G-M with the 2MB BIOS (but that has a VIA chipset).

3DMark 99 Max results. First is before regedit changes to the Ali AGP driver and second is after.

3DMark 2000 result:

The results look consistent with Phil's SS7 V3 3500 build using a DFI K6XV3+/66 - see here

PC Mark 2002:

System consists of:

Asus P5A 1.06
AMD K6-3+ 450 ACZ @ 550 MHz (5.5x100)
256MB RAM
Voodoo 3 3000 @ 183MHz
Win98SE
Latest 3dfx drivers
Ali Integrated 2.13 drivers from nVidia (2.20 wouldn't install)

Since no one's posted one yet, here's what the mod looks like on a P5A-B (AT version.) Note that the traces around the socket are rather different, but of course the pinout is the same. I circled the pins with a black marker so you can see exactly which ones to connect.

Preliminary results: extremely good! This is a 1.05 board & is definitely afflicted with the bug. SuperPi (1M) on a K6-2+/500 without the mod took ~21 minutes, after the mod it dropped to 6:17. My non-Plus K6-2 AFX ran it in 8:16 at the same clock speed. Pretty impressed.

I did a ton of 'before' benchmarks with both Intel & Cyrix CPUs, so I'll be able to determine if this mod has any effect (good or bad) on them. Will post up.

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.

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.

Hello! Has anyone checked this mod for compatibility with a Pentium 1? I'm considering doing the mod on a P5A-B v1.05, but it's important to me that my Pentium 200MHz still works when I want to switch back.

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

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.

Did you ever get around to doing any of this?

Yes, actually. But not much testing, due to lack of time. Only tested with Phil's DOS bench-pack, performance is where it should be with the III+ after the resistor mod, and I think I've settled to 1.7 or 1.8V to the CPU after the VRM mod.
Sadly board is back in storage, and it will take a while (weeks, months) until I'll build something around it. And a small correction, my board is version 1.06 not 1.05 as I previously said.

squiggly wrote on 2017-12-12, 01:30:

Will this work with other CPUs? Like if I dropped a Pentium 100 in there what would happen?

If my understanding of what he's doing with the mod is correct, it should still work with a Pentium CPU. Now if you modify the VRM to access the lower voltage-range as discussed later on, that's another story and you'd have to undo that part before running the Pentium chip. I tell you what - this may be three years too late for the O.P. but I can give this a try in about a week when the board I've ordered arrives. This should confirm whether we retain Pentium compatibility with the first mod applied.

If I'm wrong and something terrible is going to happen with an old Pentium CPU, someone please speak up and warn me! 😀