VOGONS


First post, by Azriel_Strife

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Hi everyone, I have had 2 of these boards and both of them have had the same issue.

The first board posted ok for a while, and then stopped out of the blue. It would not maintain CMOS settings and after each post it would claim a bad cmos checksum and revert to defaults. The 3v lithium battery in the board was known good, and I even tried others.

The second board is doing the same CMOS checksum bad thing. Again, batteries are good and it's not throwing any beep codes. You can change anything in the CMOS, or nothing at all, and it will still revert to defaults.

I have my 5x86 amd 133 running at 160mhz (4x40) mhz with the voltage jumper set to 4v, it wont post on the 3v setting. I've also tried posting at 133 but still no good unless i'm at 4v. Though the CMOS settings are the biggest issue at the moment.

Any help would be very greatly appreciated!

Reply 1 of 7, by Azriel_Strife

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Just for reference, the battery is at 3.10v, I have tried to trace the battery power from the battery but i'm not very good at this kind of thing.

It leads to a diode labelled "d3" about half an inch from the battery, after the diode the voltage on that line is 2.81v. I have not managed to find where this leads though. I do however know that the cmos chip itself is not getting any power on any of the pins. I checked each one and there is no voltage at all at the cmos chip.

**EDIT**

I've traced the 2.81v line i found down to where it goes behind the southbridge chipset. it comes out on the chipset side of the board and i'm blind from there. I found a couple lines coming from the chipset that show 1.01v and 1.28v, but I can't find their path to the CMOS chip. I'm so close, I just need to fix this board so i can use it!

Reply 2 of 7, by feipoa

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What voltage is actually getting to the CPU? Measure Vcc to Vss. If it is only 3.3V, try running at 100MHz. Use conservative CMOS timings for testing purposes.

Plan your life wisely, you'll be dead before you know it.

Reply 3 of 7, by Azriel_Strife

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That's the problem, the cmos will not keep any settings, it resets the defaults every time it posts even if you keep the power on.

The computer is stable at 160mhz at 4v setting. but it's useless if i can't set the bios. I'm also not sure where to measure vcc to vss.

Reply 4 of 7, by feipoa

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If your board has an AWARD BIOS, you can use Modbin to edit the default settings of the BIOS, then save the BIOS, and flash it to motherboard. This will solve the issue of the settings being reset, because they will be reset to what you set them to using Modbin. The drawback is that the time still will not be updated.

Look at the spec sheet for the Am5x86. There is a diagram which shows what all the pins are. Measure Vcc (voltage from the MB's voltage regulator) to Vss (ground).

Also, ensure that you have your BIOS set for the proper voltage, that is, either 5V or 12V. This may be your issue with the CMOS settings not being saved, that is, assuming your battery is connected properly.

Plan your life wisely, you'll be dead before you know it.

Reply 5 of 7, by Azriel_Strife

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I don't know of a setting in bios that allows me to set the voltage. I still have not been able to trace the battery voltage beyond the southbridge chip where it's obscured from sight. I've been looking with a voltmeter with no luck. At one point i had voltage at the bios chip slot, but I don't have it anymore.

Reply 6 of 7, by feipoa

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You would have to modify the motherboard's voltage regulator circuit to adjust the CPU voltage. This normally involves changing out a resistor.

Plan your life wisely, you'll be dead before you know it.

Reply 7 of 7, by Azriel_Strife

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Well first things first I need to get it working and saving bios settings. No point in anything else till then.

It runs fine at the 4v setting (actually 3.7v) at 166mhz which is fine with me.