VOGONS


First post, by vetz

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I just got hold of a 430HX and 430FX board. The 430HX board has a compatible BENCHMARQ3287 / DALLAS 12887 / ODIN 12C887 RTC onboard. When I booted it up settings were set to default and the year was 2009. I entered the current date and switched some settings before I rebooted. I enter the BIOS again and see the date is saved, but my settings are not. I guess the battery is failing and the voltage is barely enough to keep the clock running while not being able to save any settings in the CMOS RAM. If there is any other reasons behind this behavior, please let me know!

Anyway, since the 430FX board is missing it's RTC chip I unplug it from the HX board and plug it in the FX board(manual says it requires a Dallas compatible RTC, which I guess will work with any 5V 18pin RTC???). Nothing happens when I try to boot the FX board (except the 3 lights on the keyboard blinking when power is turned on). I try replugging it into my 430HX board and now it is completely dead. Won't even boot (keyboard blinks though).

1. Will an old motherboard not boot if the RTC battery is completely dead?
2. Did my swap of the RTC chip kill any remaining voltage, or did I fry something because of compatibility issues?
3. I'll probably buy some new RTC chips from Ebay as they are 4 dollars a piece with shipping from China:

This is the chip that came with the 430HX board:
http://www.ebay.com/itm/1-piece-M48T86PC1-IC- … Y-/300864180914

The manual says BENCHMARQ3287 / DALLAS 12887 / ODIN 12C887 will work, so then I guess this chip will work as an replacement? Please notice that there are missing some pins:
http://www.ebay.co.uk/itm/IC-MAXIM-DALLAS-DIP … =item3a705e08dc

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Reply 1 of 17, by vetz

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When I take a closer look I now see that I may have plugged the RTC the wrong way into the 430FX board. The socket is placed the opposite way compared to the HX board .I can't remember which way I placed it in, but I guess this can be enough to fry the RTC or? (Hopefully not the board!)

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Reply 2 of 17, by Jolaes76

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I can confirm that a dead RTC can prevent you from booting to the OS.

I have recently bought a GA586DX dual P1 board which had been packed up to sell about a year ago. Screenshoots made at that point proved that the Odin chip still could hold the data and the motherboard tried to access boot devices.

When I got the board, the RTC battery was dead flat and at POST the board complained that "no keyboard present" - but a working keyboard WAS attached and the leds on it was lit up on self-test!

So the first thing I did was to replace the Odin with a new Maxim and voila, it boots again.

It is very unlikely that you have fried the motherboard with the misplaced RTC. The RTC battery might be flat, of course.

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Reply 4 of 17, by Jolaes76

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Yes,

the board would POST with "CMOS checksum error", "Floppy disk(s) failed" and "no keyboard present"

(by memory, actual wording may be different)

the attached photo is from the advertisement when the RTC battery still had some charge

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Last edited by Jolaes76 on 2013-06-27, 06:09. Edited 1 time in total.

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Reply 5 of 17, by dirkmirk

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I had a old AT pentium pro motherboard that prevented me from booting with a dead Dallas battery, you literally couldn't do anything and the message stated a problem with the settings/and or battery, I tossed that mainboard in the bin.

Reply 6 of 17, by Jolaes76

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I guess you would not do the same now, knowing the prices of Pentium Pro boards... especially if the RTC is socketed.

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Reply 7 of 17, by feipoa

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I can also confirm that some (all?) RTC-dependent motherboards will not POST with a dead RTC.

If you plug in an RTC backwards, you are putting voltage to the RTC's GND pin and GND to the RTC's voltage pin.

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Reply 8 of 17, by vetz

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feipoa wrote:

I can also confirm that some (all?) RTC-dependent motherboards will not POST with a dead RTC.

I have three RTC based Socket 5/7 boards. All of them behave the same way and the only thing they have in common is that the RTC is dead. It has to be the reason why they will not POST (black screen).

I'm in the process of moving atm, so unfortunately eveyrthing is packed into boxes, so I won't be able to test out new chips or solder on new coin batteries.

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Reply 9 of 17, by 386_junkie

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Sorry to bring up an old thread, but... it saves me from starting a new one on the exact same topic!

I seem to be at this junction... have recently aquired a few boards with RTC's, and none of them want to POST. One or two of them were sold as untested and hence were not expensive... so I may try my hand at trying to revive them by way of replacing the RTC's with compatibles / or mod the unit to accomodate a coin-cell.

How did you get on Vetz with your motherboards? Did you attempt to replace the RTC's... and did that revive any of them?

Thanks

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Reply 10 of 17, by feipoa

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386_junkie - It is often not the fact that the RTC battery is dead that causes the non-bootable condition, it is the inability to save CMOS settings. If the default CMOS settings are not correct for your hardware configuration, it will get hung-up. I have corrected this in the past by opening my BIOS with MODBIN (on a different, Windows computer) and adjusted all the default CMOS settings to what I would save them for with my given hardware configuration. I still get the CMOS battery low error, but I can press F1 to continue and it boots as it should.

For this to work, you will need to physically remove your EEPROM chip and either hot-flash it in a different motherboard, or flash it in an external programmer.

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Reply 11 of 17, by 386_junkie

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feipoa wrote:

386_junkie - It is often not the fact that the RTC battery is dead that causes the non-bootable condition, it is the inability to save CMOS settings. If the default CMOS settings are not correct for your hardware configuration, it will get hung-up. I have corrected this in the past by opening my BIOS with MODBIN (on a different, Windows computer) and adjusted all the default CMOS settings to what I would save them for with my given hardware configuration. I still get the CMOS battery low error, but I can press F1 to continue and it boots as it should.

For this to work, you will need to physically remove your EEPROM chip and either hot-flash it in a different motherboard, or flash it in an external programmer.

I'm starting to tread in unfamiliar territory here.

So let me try relay my understanding of this... what you are saying is; because the RTC is dead CMOS settings are lost which cause the non-bootable condition. In order to get the system to boot... the BIOS should be opened with an assembler (on a difference machine) with the settings changed to match the system you want to boot / or default. Then replaced back into the board from which it came to then be able to boot the system when powered on?

I previously thought all that was required was to give the RTC more (constant) juice with a rechargable coin-cell attached and the system would boot up ok again, but really it should boot up regardless if the RTC has power or not... just s long as the CMOS setting match the hardware config?

Thanks for you explanation of this.

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Reply 12 of 17, by feipoa

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It is not the RTC that is dead, it is the RTC's battery that is dead. The RTC is still used and needed for time management even if the battery is dead.

When the RTC's battery is dead, the BIOS is trying to use whatever the EEPROM's FLASH default CMOS settings are set as. This is where the program called Modbin comes in. Every AWARD, AMI, Phoenix, etc. BIOS (via the EEPROM chip) has default CMOS settings saved into it. These default settings are set by the motherboard's manufacturer, or whoever supplies/writes the individual BIOS code for your board. As the end user, you can also edit these DEFAULT CMOS settings by opening a soft-copy of your BIOS image using a program called Modbin. You can use Modbin to change those default CMOS settings to whatever your liking is. You can also unhide various CMOS options if your board maker hid them. Note that the settings you set in your BIOS get saved in the RTC's battery, which are different from those default settings saved in the EEPROM FLASH BIOS chip.

By way of example. Say your RTC's battery dies and you can no longer save your CMOS settings on your computer. The computer tries to use the DEFAULT CMOS settings, which are saved into the EEPROM chip. These DEFAULT settings may have the memory type set for FRM memory. You go into the CMOS and try to select EDO, reboot, but that doesn't get saved because your CMOS battery is dead. Now if you are trying to use EDO memory and the BIOS is setup for FPM, you might not be able to boot. That is just one example, the same applies for if you have a 5.25" floppy set on A, when you are using a 3.5" floppy. There are dozens of examples like this which may cause your system not to boot.

In summary, you can either a) modify your RTC module to take a coin cell battery, b) replace your RTC with one which has a functional CMOS battery, c) use Modbin to adjust the EEPROM DEFAULT CMOS settings, then save this edited BIOS image to your EEPROM chip. If you are using AWARD BIOS version 4.20, 4.50, or 4.51, you should be able to use Modbin 4.50.60, 4.50.63A, or 4.50.77. Let me know if you need something.

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Reply 13 of 17, by PCBONEZ

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How is this RTC module mod done?

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Reply 14 of 17, by feipoa

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Here's a photo. http://www.mcamafia.de/mcapage0/jpg/ds1287rw.gif

That method seems to leave the dead internal battery connected. I seem to recall another method which cuts open the top hat and disconnects the internal battery.

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Reply 15 of 17, by PCBONEZ

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Thank you.

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Reply 16 of 17, by 386_junkie

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feipoa wrote:

Here's a photo. http://www.mcamafia.de/mcapage0/jpg/ds1287rw.gif

That method seems to leave the dead internal battery connected. I seem to recall another method which cuts open the top hat and disconnects the internal battery.

Awesome pic! 😀

Yea, from what i've learned so far... this method seems to be a little cleaner, with much of the RTC still intact.

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Reply 17 of 17, by sunaiac

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Oow, I thought I had killed my shuttle HOT-433 but it might be than the RTC battery is dead then.
One more thing on my never shrinking TODO list then 😁

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