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View Full Version : CMOS checksum error, goes into boot loop



Flamin Joe
February 22nd, 2016, 06:59 PM
Hi all,

I recently picked up an Atari PC4 Motherboard (286) which has an issue with booting properly. To give you some details on the board it has an AMD 286-16 CPU, C&T Chipset, AMI BIOS and it uses SIPP RAM for all it's memory capacity (there's no mixture of SIPP and socketed chips like I've seen on some older 286 boards). In case it's relevant it has onboard EGA/VGA via a Paradise PVGA. I thought I would explain this all first since you don't see these motherboards around much so I'm guessing not many would be familiar with it.

Anyway getting to the problem at hand, the board will display and count up the memory correctly with no errors but then it beeps twice and displays the following message:

XCMOS checksum error
CMOS system options not set
CMOS display type mismatch

Interestingly after a second or so it beeps just the one time which to me sounds like the familiar "POST OK" beep but then resets and starts all over again. The beeps are definitely clearly apart so I'm assuming it's just the "2 beep" error code but even if it was 3 beeps the errors are closely related. I tried attaching a floppy drive to the onboard floppy port to see if I could get it to boot off that for further diagnosis but it doesn't even attempt to do so (restarts as I said above).

According to the AMI BIOS beep code, 2 beeps is "Memory parity error" which stated on the below website is "A memory parity error has occurred in the first 64K of RAM. The RAM IC is probably bad."

http://www.bioscentral.com/beepcodes/amibeep.htm

Things I've tried:

1. Tried different RAM and also in different positions. Same result. The RAM it came with was the original RAM they were sold with.
2. Different external batteries which I know are working from other PC's I have (they use the same battery). Still get the CMOS setting errors.

Is there something else I need to look at on the motherboard which could be causing the fault? I'm afraid while I started on PC's in this era when I was young, all my diagnosing and troubleshooting skills I learnt with later PC's so when it comes to old architecture like this, besides the basics I'm a little lost as to where to look on the board for a fault and a lack of schematics doesn't help. So would appreciate any help you guys could provide in pointing me in the right direction. :D

Thanks!

Flamin Joe
February 22nd, 2016, 07:07 PM
Something just occured to me regarding the beep codes. Is it possible for there to be two beep codes occuring during the same POST? 1 short beep is "DRAM refresh failure". It just strikes me as odd that the one beep was the POST OK beep considering the issues I'm having and I may have overlooked this.

SpidersWeb
February 22nd, 2016, 08:12 PM
Sounds like you needs to install a new battery, then boot a dos disk and run the setup program again. GSETUP or similar should get you sorted.

CMOS Checksum error - the junk in the CMOS memory doesn't calculate the same checksum I was expecting
CMOS system options not set - the junk in the CMOS memory isn't giving me a valid configuration :(
CMOS display type mismatch - the junk in the CMOS memory doesn't match the display type I just booted with?

Messages sound scarier than they really are. Basically the battery went flat, and it lost the contents of it's CMOS memory.

Flamin Joe
February 22nd, 2016, 09:35 PM
I'm familiar with the CMOS errors which is why I tried several other 6V batteries I have of the same type and it made no difference. An option comes up on the BIOS screen to press DEL to enter SETUP/EXTD-SET but it won't allow me to enter setup when pressed. I know it is receiving key presses OK as I can skip the memory test by pressing ESC and if I hit DEL too many times it adds "keyboard error" to the list of errors.

I just can't seem to get it out of this boot loop regardless if I try different batteries.

retrogear
February 23rd, 2016, 06:36 AM
Keep the floppy connected. Try holding INSERT key as you boot to see if there is a change, watch for floppy access. Also press DEL when prompted to and see if floppy is accessed.

Flamin Joe
February 24th, 2016, 01:50 AM
Keep the floppy connected. Try holding INSERT key as you boot to see if there is a change, watch for floppy access. Also press DEL when prompted to and see if floppy is accessed.

No change, it still goes through the boot loop and there is no drive seek occuring.

Holding down DEL does nothing but add "keyboard error" as I mentioned previously.

Holding down INSERT adds the line to the top "INS" key pressed, XCMOS data ignored" and like DEL adds "keyboard error" to the list of errors.

kyodai
February 24th, 2016, 02:42 AM
If a battery doesn't help and you can't enter setup then most probably the BIOS is corrupted.

On older AMI BIOS you could flash the BIOS during startup by pressing CTRL+HOME and having a floppy with amiboot.rom inserted. If that also won't work you will need to replace the BIOS chip.

1ST1
February 24th, 2016, 09:31 AM
1. Remove battery
2. Remove power supply
3. Get a piece of wire and connect it on one side on mainboard ground
4. touch with the other end of that wire all pins of the 82c206 chip. This will securely erase all datas of the CMOS.

It also could be that the 82c206 chip is broken, this one includes the cmos ram. It's possible that I still have a few of them. I also remember that I had the C&T neat chipset utilities diskette in my hands a few weeks ago.

Addtionally you might find here something: http://www.ataripc.net/pc4-286/

Flamin Joe
February 25th, 2016, 02:17 AM
If a battery doesn't help and you can't enter setup then most probably the BIOS is corrupted.

On older AMI BIOS you could flash the BIOS during startup by pressing CTRL+HOME and having a floppy with amiboot.rom inserted. If that also won't work you will need to replace the BIOS chip.

This has ODD and EVEN BIOS chips so I don't think that is applicable in this case. If the BIOS is faulty that would be a real bummer I was hoping to eventually do a BIOS dump to preserve them. :(


1. Remove battery
2. Remove power supply
3. Get a piece of wire and connect it on one side on mainboard ground
4. touch with the other end of that wire all pins of the 82c206 chip. This will securely erase all datas of the CMOS.

It also could be that the 82c206 chip is broken, this one includes the cmos ram. It's possible that I still have a few of them. I also remember that I had the C&T neat chipset utilities diskette in my hands a few weeks ago.

I tried what you suggested (although I'm not 100% sure I did it correctly) and it made no difference. Unfortunately too if the chip is indeed faulty it's not going to be a easy replacement as it's soldered directly onto the motherboard not socketed.


Addtionally you might find here something: http://www.ataripc.net/pc4-286/

*ahem* see signature. :D

1ST1
February 25th, 2016, 11:11 AM
Oh, that's you... Thanks for the things you offered to download for the PC3, I have one and these files were very usefull, that PC makes a lot of fun. Anyhow, why you don't have no details about the ABC series on your side? They are different from PC1-5. Under downloads for PC4 you just offer a documet for ABC-286, but thats a different machine than PC4.

kyodai
February 25th, 2016, 12:21 PM
This has ODD and EVEN BIOS chips so I don't think that is applicable in this case. If the BIOS is faulty that would be a real bummer I was hoping to eventually do a BIOS dump to preserve them. :(


Wow, odd and even BIOS chips. last time i saw that was on an ancient IBM i think, but that was waaaaaaay older than a 286... Prolly can not be flashed then... But weird to see that in a 286. well Atari was always special, eh?

Well if the BIOS is not corrupted then there is not much left i could think of. Since it resets at the moment when you expect it to boot i would only come up with a broken Floppy drive controller or so. But even in that case I'd have expected it to enter setup, but maybe it initializes the controller before setup, then just resets because it is broken? Only guess i can come up with for now.

Stone
February 25th, 2016, 12:31 PM
Wow, odd and even BIOS chips. last time i saw that was on an ancient IBM i think, but that was waaaaaaay older than a 286... Prolly can not be flashed then... But weird to see that in a 286. well Atari was always special, eh?I have a 286 with a WD motherboard and a Faraday chipset with odd/even BIOS chips. It was my first computer. :-)

SpidersWeb
February 25th, 2016, 01:16 PM
Some stupid questions:
When you say you press DEL (don't hold it down, just once when it asks) are you using the Delete key, or the "Del" key on the numeric keypad?
Have you tried another keyboard or tested that particular key works on another computer?

Flamin Joe
February 25th, 2016, 01:55 PM
Oh, that's you... Thanks for the things you offered to download for the PC3, I have one and these files were very usefull, that PC makes a lot of fun. Anyhow, why you don't have no details about the ABC series on your side? They are different from PC1-5. Under downloads for PC4 you just offer a documet for ABC-286, but thats a different machine than PC4.

Thanks, I'm glad to see my site is of use to someone. :D

The decision not to include the ABC series is a personal one. I prefer to focus just on the original Atari PCx series as the Atari PC3 was my first experience with PC's so I suppose holds more sentimental value for me. They also are in my opinion more "Atari" in their look and feel (although as the series progressed it became less and less) whereas the ABC series were more generic much like the many other IBM PC clones that were released around that time. The Atari Technical Bulletin you refer to is for both the ABC286 and PC4X as it's described in the document (the "X" denotes more than one within that series as it came with either a 12 or 16MHz processor). That's why it has been included under PC4.


Wow, odd and even BIOS chips. last time i saw that was on an ancient IBM i think, but that was waaaaaaay older than a 286... Prolly can not be flashed then... But weird to see that in a 286. well Atari was always special, eh?

Well if the BIOS is not corrupted then there is not much left i could think of. Since it resets at the moment when you expect it to boot i would only come up with a broken Floppy drive controller or so. But even in that case I'd have expected it to enter setup, but maybe it initializes the controller before setup, then just resets because it is broken? Only guess i can come up with for now.

I do have a couple of ISA floppy controllers lying around so I might give one of them a try on the off chance it might do something. Hopefully that won't require disabling the onboard floppy controller as I have no idea which jumper would do that. Information on these PC's are pretty scarce (one of the main driving forces behind my website), I have no schematics, no manual which probably wouldn't go into that much detail if the PC3 manual is anything to go by, and I only know of one other person who has this particular motherboard and he is on the other side of the world!


Some stupid questions:
When you say you press DEL (don't hold it down, just once when it asks) are you using the Delete key, or the "Del" key on the numeric keypad?
Have you tried another keyboard or tested that particular key works on another computer?

Definitely pressing the Delete Key and I know it works as I've used it on both a 386 and 486 system and never had an issue. One thing to note I'm currently using a PS/2 keyboard with a PS/2 to AT adapter if that makes any difference which I'm assuming it wouldn't. I've got plenty of XT keyboards but no AT keyboard as yet which I hope to rectify soon.

SpidersWeb
February 25th, 2016, 04:33 PM
Definitely pressing the Delete Key and I know it works as I've used it on both a 386 and 486 system and never had an issue. One thing to note I'm currently using a PS/2 keyboard with a PS/2 to AT adapter if that makes any difference which I'm assuming it wouldn't. I've got plenty of XT keyboards but no AT keyboard as yet which I hope to rectify soon.

Try "Del" instead of Delete if you haven't already. Just mentioning it because it caught me out a few weeks ago on one system I was working on.
Might be nothing, but it's worthwhile eliminating these things. The CMOS errors wont go away until you get in to setup and save your settings.

Flamin Joe
February 26th, 2016, 05:44 PM
Try "Del" instead of Delete if you haven't already. Just mentioning it because it caught me out a few weeks ago on one system I was working on.
Might be nothing, but it's worthwhile eliminating these things. The CMOS errors wont go away until you get in to setup and save your settings.

Tried both, still no luck.

I ended up buying a Willem EEPROM programmer which will arrive next week. It's been on my to buy list for quite some time figured now would be a good a time as any to take the plunge. Plan is to get a couple of new EEPROM's and see if any of the AMI 286 BIOS's that are available on the net will work with this motherboard. If so that will at least allow me to determine if the ROM is faulty or if the problem lies further such as with the 82c206 chip as mentioned previously.

1ST1
February 26th, 2016, 09:49 PM
Wow, odd and even BIOS chips. last time i saw that was on an ancient IBM i think, but that was waaaaaaay older than a 286...

Olivetti M24 / AT&T 6300 has it as well as it's 8086.

@FlamingnJoe - please include ABC series on your site. Informations about these are very rare, and they have beautyful design.

Flamin Joe
February 27th, 2016, 08:08 PM
@FlamingnJoe - please include ABC series on your site. Informations about these are very rare, and they have beautyful design.

I may sometime in the future but as it is I don't have much time to devote to the Atari PC series as it is so taking on the ABC series is a low priority. Also a lot of the detailed information I have on my website came from actual PC's, components, manuals, disks, schematics I own which has taken time and money to aquire. If I was to go into the same level of detail with the ABC's ideally I would have to do the same and find this stuff which is pretty rare and most of the time on the other side of the world so expensive to acquire.

The alternative is going around and copying information I find on the net on the ABC's but then I would be doing what frustrated me with the Atari PC's. There are quite a few Atari websites that mention the series (some even go into some good detail with extra photos) but I also found a lot of details missing and conflicting information most likely from them just simply copying what they found on another site. I don't want to be doing that as well.

I hope you understand. :D

1ST1
February 27th, 2016, 11:30 PM
I understand, anyhow they are missing on the otherwise best site about ATARI PCs. If you start by just list the ABCs with their basic specs, add a photo, that already would help. The rest might come from community.