Um, the 50mhz setting is documented on TH99. JP28 on 1-2, the others on 2-3.

Old Thrashbarg wrote:

Um, the 50mhz setting is documented on TH99. JP28 on 1-2, the others on 2-3.

Thanks very much! But it's bizarre that this info is not printed in the manual which came with the mobo; PCB revision 1.8. The copyright blurb at the beginning of the manual says that the manual revision is 2.0, and it applies to PCB revisions 1.21 and up. Oh well.

Anyway, thanks a lot for the heads-up! I'll give this a go first thing tomorrow morning...

retro games 100 wrote:

Old Thrashbarg wrote:

Um, the 50mhz setting is documented on TH99. JP28 on 1-2, the others on 2-3.

Thanks very much! But it's bizarre that this info is not printed in the manual which came with the mobo; PCB revision 1.8. The copyright blurb at the beginning of the manual says that the manual revision is 2.0, and it applies to PCB revisions 1.21 and up. Oh well.

Anyway, thanks a lot for the heads-up! I'll give this a go first thing tomorrow morning...

It's not unthinkable ASUS found out the board often had troubles with the 50Mhz FSB and oficially stopped supporting 50Mhz FSB on later revisions?

They omitted the setting because the board doesn't have a FSB/PCI clock divider, which means a 50 MHz PCI bus. I can't imagine any PCI card working reliably at that speed.

The rest of the board should work fine at 50 MHz FSB, as long as you set slower timings for the cache and enable the asynchronous 7.159 MHz clock for the ISA bus.

Keep an ISA VGA card ready 😉

The reason I want to do this is because I want to see if it's possible to run an AMD P75 133 MHz CPU @ 200 MHz. That would be a 4x multi and a 50 MHz bus speed = 200 MHz. My thinking is - why restrict this P75 overclock speed of 200 MHz to UMC chipset based mobos?

How is your progress? (:

udam_u wrote:

How is your progress? (:

Hehe! Firstly, thanks very much for all the info so far! I'm itching to get started on this project. I've located all the components needed, inside the attic of doom. The problem is that the postman delivered another load of junk today, and I just want to get that stuff tested. I'm nearly finished. I hope to start on the Asus 486 + 50 MHz bus project either tonight, or tomorrow morning. Sorry to keep you in suspense! 😀

He he he ok - I'm waiting impatiently. ^^

retro games 100 wrote:

udam_u wrote:

How is your progress? (:

Hehe! Firstly, thanks very much for all the info so far! I'm itching to get started on this project. I've located all the components needed, inside the attic of doom. The problem is that the postman delivered another load of junk today, and I just want to get that stuff tested. I'm nearly finished. I hope to start on the Asus 486 + 50 MHz bus project either tonight, or tomorrow morning. Sorry to keep you in suspense! 😀

Gahhhh...I still have a pile of 1 meter to go. And those Voodoo3 3500TV's sure aren't helping LoL!

But anyway, I'll need to clean up the graphics cards first anyway (clean contacts with rubbing alcohol).

But anyway, I'll need to clean up the graphics cards first anyway (clean contacts with rubbing alcohol).

Random tip: pencil eraser. I've found that a couple passes on each side with an eraser does a more thorough job and quicker than alcohol. It's become part of my routine anytime I install a card or stick of RAM that's been sitting for awhile.

I got this Asus mobo working fine @ 50 MHz bus speed. Quake 1 in DOS works. But I've got the P75 CPU running at its 3x multi, with a CPU clock speed of 150 MHz. I haven't tried its 4x multi yet. It's 12:20 AM now, and so I'll try the 4x multi out first thing in the morning. BTW, I had to bypass the mobo's integrated IDE to get MS-DOS to boot. I disabled it in the BIOS, and used an ISA-based IO controller card instead. Also for the VGA card, I am using a PCI one - it's my good old trusty Virge 325 by Number 9. Also to follow in the morning, benchmark screenshots, etc!

Edit: There's no 5V jumper on the mobo. How do I tell the mobo I want to send 5V through the P75 chip? I'll almost certainly want to do that, if the 4x multi @ 50 MHz bus speed test is to succeed.

Old Thrashbarg wrote:

But anyway, I'll need to clean up the graphics cards first anyway (clean contacts with rubbing alcohol).

Random tip: pencil eraser. I've found that a couple passes on each side with an eraser does a more thorough job and quicker than alcohol. It's become part of my routine anytime I install a card or stick of RAM that's been sitting for awhile.

Same method i use. Results are amazing compared with alcohol cleaning.

sprcorreia wrote:

Old Thrashbarg wrote:

But anyway, I'll need to clean up the graphics cards first anyway (clean contacts with rubbing alcohol).

Random tip: pencil eraser. I've found that a couple passes on each side with an eraser does a more thorough job and quicker than alcohol. It's become part of my routine anytime I install a card or stick of RAM that's been sitting for awhile.

Same method i use. Results are amazing compared with alcohol cleaning.

Really?!?
I think I'll give that a try...but I'm gonna need to get me a couple pencil erasers first 😜

So far the rubbing alcohol has "revived" hardware on more then one occasion 😀
Fixed multiple memory modules, a couple graphics cards and even a Slot 1 CPu or 2 😀
And man, some had a LOT of dirt on them!
When you look at the dirty contacts you hardly see it, but after you've cleaned them up, the paper towel is BLACK!

I got this Asus mobo working fine @ 50 MHz bus speed. Quake 1 in DOS works. But I've got the P75 CPU running at its 3x multi, with a CPU clock speed of 150 MHz.

This is great info! (: How fast is SIS chipset compared to UMC ones?

Edit: There's no 5V jumper on the mobo. How do I tell the mobo I want to send 5V through the P75 chip? I'll almost certainly want to do that, if the 4x multi @ 50 MHz bus speed test is to succeed.

What a pity! It seems that this motherboard hasn't got voltages higher than 3.6V?! Very strange as for 486 motherboard...

Yes, as I feared the lack of a specific 5V CPU setting on the mobo makes this 200 MHz test a non-starter. I tried it, and I get no POST. That's a real pity. I wonder if I have any other SiS chipset-based mobos that can (a) support the P75, and (b) have a 5V CPU voltage setting on the mobo? I'll have a look...

I'm not sure which chipset is supposed to be faster, SiS or UMC? If I can find an SiS board that can do 200 MHz, I'll be able to compare some benchmark data...

I've got a PCI 486 Soyo 4SA2 mobo. ATM it's not in front of me to look at, but I can dig it out. It's got the SiS chipset, and can accept a P75 CPU. However, looking at the Total Hardware 99 specification for it, I can't see where the voltage jumper selection is. It may be one of the "factory configured - do not alter" jumpers?

However, on this TH99 webpage (below), please look carefully at the settings for jumper JP40. There seems to be a different setting, depending on whether a CPU uses ~3.x volts or 5 volts. Maybe JP40 holds the key to altering the amount of volts that can be sent through a X5 133 P75 CPU?

http://www.artofhacking.com/th99/m/S-T/33326.htm

To see a photo of this board, please scroll down to the soyo5.JPG photo near the bottom of the page. (It isn't a very good photo.)

My new crusty socket 3 board!

Unfortunately, I couldn't get the P75 CPU to reach "top speed", but I did some more testing with this mobo @ 50 MHz bus speed. I tried several PCI cards, and they all worked except for a Virge DX, which wouldn't work at any bus speed! With an 8MB ATI 3D Rage Pro PCI installed, and the P75 running at 3x + 50 MHz = 150 MHz, I get these scores:

Quake 1 shareware 1.06 Fullscreen = 14.0 FPS
3DBench 1.0 = 90.9
PcpBench mode 100 LFB = 10.9

Inside the BIOS, I had to set the DRAM speed to "slower", otherwise MS-DOS would not boot up. All of the other BIOS timings were "maxed out".

retro games 100 wrote:

There's no 5V jumper on the mobo. How do I tell the mobo I want to send 5V through the P75 chip? I'll almost certainly want to do that, if the 4x multi @ 50 MHz bus speed test is to succeed.

That would only be possible by cutting a pin on the CPU or altering the wiring on the socket or board.

BTW, here are some old speedsys screens of my 5x86 @ 40x4=160 MHz:

@rg100
Thank you for your results! (:
Huh my cx5x86@150 is much faster than am5x86@150MHz. This is good news because I thought that something is wrong with my cx system.

If I had free time I would compare SIS, ALI and UMC 486 PCI chipsets. I wonder which is best. Everything indicates UMC... (best overclocking, flexible FSB settings, available FSB/PCI dividers) - what are your feelings on this subject?

udam_u, I think the UMC chipset based 486s appear to be a good all round performers. I would really like to see if I can get 200 MHz from other chipsets first, before declaring UMC as the winner. 😉 😀 I'm about to test a VIA chipset 486 at 200 MHz, and then I've found an SiS chipset 486 which accepts a 5x86. I hope to finish testing soon, and I'll post back with the results!

5u3, please can you tell me what pin I need to cut, in order for the P75 CPU to automatically operate at 5V? Luckily, I have a few spare ADW chips for mad overclocking experiments, and I'm happy to give this idea a go! 😀