ERROR: cannot handle A20 line!

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drugwash
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Hi! I have a GMB-P56IPS v0 motherboard (same with DTK PAM-56IPS E-0) and everything seems to work fine upon boot, until it tries to load the operating system (Win98). I'm getting the "cannot handle A20 line" error and it stays in DOS mode.
All this happened after I swapped BIOS chips with another board (different brand, but same BIOS chip and same chipset on the board). I have to mention here that this board has a Dallas RTC DS12B887, which I suspect it may be involved. BIOS chip is Winbond W29EE011-15, loaded with AWARD BIOS v4.51PG . BIOS string is 2A59GG39, version 1.05c . I've done some reading about the A20 line, but I still don't know what to do. I tried the normal/fast option in BIOS setup, with no result. I'd really need some help on this, please!
Rainbow
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Patched and tested BIOSes are at http://wims.rainbow-software.org
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drugwash
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I already have downloaded the latest BIOS for it, but the problem is that this BIOS chip has NEVER been mounted on another board, so there's no reason to think that the software contained in it might have been damaged. All I did was to put ANOTHER chip with a similar soft on THIS board. That's why I said I suspected the Dallas chip (or something else on the board) to be corrupted. I don't really know who and how controlls the A20 line phisically and also I don't know how the Dallas really works. I know it can be programmed but I don't know the way it interacts with the other components. Could the other BIOS chip have reprogrammed (a part of) the Dallas? Could it have damaged the chipset, the keyboard controller or some other component? Those are questions I need an answer to. Thanks for replying, for now. I hope I can get some enlightenment further on.
Ritchie
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I don't think Rainbow thought your BIOS chip may have been damaged; rather the image flashed onto it may have been giving you a compatibility problem.

I would try loading the default settings in the BIOS. If that does not work I suspect your mainboard may be faulty.

As for Dallas, I do no tknow much about it, but if you suspect this is playing a role, try disabling Dallas in the BIOS if you can (it may not be something that can be enabled or disabled).
KachiWachi
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Note that he is using the words "similar" and "different brand, but same BIOS chip and same chipset on the board".

This might be a plain and simple BIOS incompatibitlty problem.

If I remember, the A20 line runs off the keyboard chip (or not in "fast" mode), which might be a different chip in this board than in the parent board.

You said you downloaded the correct BIOS for your board, but did you install it? Flash in the correct BIOS for your current board, and see what happens.
NickS
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Assuming you fitted the alien BIOS temporarily and have reverted to the original;
The Dallas DS12B887 RTC chip is a combined battery, CMOS and RTC chip. If the other BIOS has affected the extended CMOS settings, you could be in trouble as I believe there may be no "CMOS clear" facility
(see here. However, other documents suggest pin 21 may be a "CMOS clear" pin.
As the PC stays in DOS mode, I guess you are able to use a keyboard? If so, try looking for an old DOS utility which will clear/reset the (extended) CMOS (maybe BIOS 1.35.x at bioscentral.com).
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drugwash
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NickS is right, that's what I did.
I cleared the CMOS, though, or at least that's what it looked like. I had to "hot-clear" it, meaning power on with the clearing jumper in the "clear" position, because the "cold-clear" wouldn't work.
Using the /M:x parameter in the config.sys for loading himem.sys didn't give me that errror anymore, but further on loading the system files I got a "Windows protection error. The system has to be restarted" message. I used several values for the x,although not all the available ones, with no change, except one time when it completely froze the system.
As soon as I get a spare floppy unit, I'll try to flash the latest BIOS version to the chip, maybe that's what it's all about, after all. Or, question: could I flash it from the HDD, after Shift+F5, without using a floppy?
Meanwhile, some more good ideas are welcome.
Ritchie
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Drugwash - Looking at your two posts, so far, again:

I don't think installing a different physical BIOS chip would have damaged your board, unless damage occurred during the physical installation process (unlikely if you taken care and had no power applied during the physical installation) or unless you overlooked voltage requirement differences between the chip that was there and the chip that is there now.

Your board is probably fine, especially if the keyboard works, and probably although the boards were similar I suspect most likely differences between the BIOS images on the two chips are responsible for the BIOS image on the currently installed chip not quite being correct for the baord. Either that or the settings need to be cleared and reset to defaults.

You have said that the BIOS chip installed now has never been mounted on another board. However, if the BIOS image on the chip you installed was for a different brand, model or even a different revision board than the one you have installed it onto, it is likely that the BIOS image is not quite correct for the board you have installed it onto, even though as you say the boards are similar. In this case the best way to obtain a recent and compatible BIOS would be to simply download and flash the latest BIOS for your board.

As for clearing the BIOS, if there are no clear CMOS jumpers and no removable battery, I believe you can short the two contacts on the old style soldered batteries to cause the battery to lose it's power (but use at own risk).
Ritchie
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Hi there Drugwash

Sorry my post came a bit late.

I suspect that because the image on the chip you installed was for a similar board that therefore the image does not quite correctly match the board which it is now installed onto, and therefore flashing the latest BIOS for the board it is installed onto is a good idea. Hopefully this solves your problems.

Possibly though the O/S just requires reinstalling, although if it were me I would flash the BIOS anyway. Once the flash is performed it is probably a good idea to reinstall Windows as it has been through a few different BIOS images and BIOS configuration changes - Windows may in fact refuse to run properly because of this reason and may therefore require a reinstall before things run properly again.
KachiWachi
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Just as long as you can successfully boot to a pure DOS mode (Safe Mode Command Prompt Only), you can copy the flasher and BIOS image to your HD and flash from it.
drugwash
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Well, Rainbow was right from the very beginning. I flashed the latest BIOS version onto the chip and everything is fine, so far. Listening to his advice then, would have spared all of us from this brain-squeezing... But, then again, somebody else might benefit from this talk, so it might have not been useless, after all. Thanks again, all of you! Cheers!
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