Corrupt CMOS even after battery change Sharp PC-7200

[Coder]

Hello everyone. I have a Sharp PC-7200 that when booting complains of "Invalid configuration information" and says to "Strike F1 to continue". When I got it, the original CMOS battery was dead, as you might expect. I've replaced it with the same voltage Ni-MH battery, and it now stores settings and keeps time. But on boot, it still complains of "Invalid configuration information". You can press Alt+Ctrl+Setup to get into the BIOS configuration, but not all BIOS values are exposed to the user, and I suspect something that's not exposed has become corrupt. I have some questions that I hope someone here can answer with some sort of authority:

1. Shouldn't the default CMOS configuration get loaded if the CMOS battery is unattached? It definitely was while I changed the battery. It was completely detached for at least a few minutes.
2. If the default CMOS configuration was supposed to get loaded but it's still complaining of it being invalid, would that indicate bad CMOS RAM? Or could it be that the DIP switches on the back are in an invalid state?
3. Is there a way to set the configuration other than through the built in setup utility? I've heard there is a universal configuration disk, but I can't find any information on it now. Would it work on a computer as non-standard as these Sharps? Would it hurt anything to try?
4. If the CMOS RAM ends up being bad, can it be replaced? Is it possible that this could be a bad BIOS ROM?
5. Right now, everything seems to work except it will neither boot off the hard drive nor detect it when booting from the floppy drive and using FDISK. But on startup, the drive spins up and initializes and the HDD LED lights momentarily after the Floppy one does during its initial checks.

 

[daver2]

I will ask the dumb question...

You are going into the CMOS RAM on power-up, configuring it properly and then saving the configuration aren't you?

This configuration should then be remembered over a power cycle.

If you are doing this, and the settings are not being remembered, then there is definitely something more wrong.

Dave

 

[Coder]

Hi Dave. I meant to mention that I can set any of the available values and they are properly stored after power cycling, but the message remains. Also of note, on the first boot after replacing the CMOS battery, when I would expect the computer to be using it's default values for everything, the date and time both contained invalid values. The time had a weird character for the hour value, and the date had an impossible date assigned; something like 18/31/1980. I don't remember the actual value that was set. Once I updated them with a valid date and time, they seem to be keeping time correctly. I've been able to unplug the unit and still the time is kept and the other values I changed are saved. But still I get the invalid configuration message.

 

[daver2]

When the battery is "dead" you will just get random rubbish in the date and time.

I would suggest leaving the power off for 24 hours to see what happens over a longer period of time.

Interesting...

Let me think a bit more...

Dave

 

[daver2]

Is this of any help?

https://forum.vcfed.org/index.php?threads/sharp-pc-7200-cant-get-any-to-bootdisk-to-work.253/

In particular the last post...

Dave

 

[modem7]

Shouldn't the default CMOS configuration get loaded if the CMOS battery is unattached? It definitely was while I changed the battery. It was completely detached for at least a few minutes.

As an example, the IBM AT doesn't load default values.

If the default CMOS configuration was supposed to get loaded but it's still complaining of it being invalid, would that indicate bad CMOS RAM?

If there was faulty RAM in the CMOS/RTC chip, I would expect one of the following:
1. If the POST checks that RAM, you would see a code/message indicating something along the lines of 'bad CMOS RAM'. (Followed by the machine halting.)
2. An error message along the lines of 'Bad CMOS checksum'.

I've heard there is a universal configuration disk, but I can't find any information on it now. Would it work on a computer as non-standard as these Sharps? Would it hurt anything to try?

That sounds like GSETUP.EXE, short for 'generic setup'. But true universal/generic SETUP software does not exist.

The PC-7200's service manual indicates that extra information is stored, such as "Backlight timeout'.

If the CMOS RAM ends up being bad, can it be replaced?

Refer to [here]. It is a chip replacement. One just has to identify the particular chip in use on the motherboard for CMOS/RTC functionality. The PC-7200's service manual indicates that an MC146818 chip is used.

Is it possible that this could be a bad BIOS ROM?

I doubt that very much.

"Invalid configuration information"

The question is, what does Sharp define as "invalid".
An authoritative source is the source listing for the motherboard BIOS, but that has been excluded from the PC-7200's service manual (which is comprehensive).
Might examples of Sharp's "invalid" be:

1. SETUP configuration indicates that an 80287 NPU is fitted, but the POST cannot find one. (E.g. User error - NPU not fitted.) (E.g. Faulty NPU.)

2. SETUP configuration indicates that a 1.2M floppy drive is fitted, but the POST thinks that a 360K drive is fitted. (E.g. User error - a 360K is fitted.) (E.g. Faulty 1.2M drive - stepping problems - POST can step drive to track 5 but not to track 45 and so assumes that a 40-track drive is fitted.)

 

[BlaBla1985]

Right now, everything seems to work except it will neither boot off the hard drive nor detect it when booting from the floppy drive and using FDISK. But on startup, the drive spins up and initializes and the HDD LED lights momentarily after the Floppy one does during its initial checks.

From my own experience with the PC7200 I don't think that message will ever go away, unless you can magic that hard disk back to life. I have 2 of these machines and neither have a working hard disk.

You can even put an XT IDE in the expansion slot at the bottom and install DOS on the CF card and it will still complain about the settings, but otherwise work completely fine. After pressing the key to continu it will just load the XT IDE bios and boot to DOS.

As is the case with the other PC 7xxx machines by Sharp, their BIOS is a bit non standard.

There is a configuration disk for the PC 7200... I think... I need to look up the disk set that came with one of the machines I have.

 

[daver2]

>>> There is a configuration disk for the PC 7200... I think... I need to look up the disk set that came with one of the machines I have.

Which is what the thread/post I linked to previously stated.

You may need to run this utility to clear the error.

Dave

 

[BlaBla1985]

Which is what the thread/post I linked to previously stated.

You may need to run this utility to clear the error.

Yes, I looked at it and it ends on the note that you should end up at the C: prompt... which sounds like you need a working hard disk to get to that. The hard disk controller is a weird little board that plugs in somewhere that connects to a fairly small (in dimensions... 3,5 inch I guess) 20MB harddisk. (The model number 7221 stands for PC7200, 20MB hard disk, 1 floppy drive.)

I wanted to try the diag disk that came with mine... but I think the floppy drive needs a clean. Odd thing is, the DOS 3.2 bootdisk that came with it is a 1.2MB disk, which fits with the 1.2MB drive and does work (although a bit noisy). The Diag disk is a 360K DD disk and doesn't want to work at all (neither the original disk and the back up I made). A generic MS DOS 5.0 bootdisk 360K DD does boot but makes a lot of noise...

Edit: And I did test the Diag disk in another system (a PC7100) and it does work in a 360K drive... although de Diag program can't run on that system ofcourse.

I'm pretty sure I was able to use the Diag disk before but it never fixed the message at startup (then again, I was never that bothered by it showing up)

 

[daver2]

C: if you have booted from a hard disk.

A: or B: if you boot from a floppy of course.

There may be some compatability issues between a 1.2 MB drive and 360 KB media. I would have to go and check though.

Dave

 

[BlaBla1985]

Yeah... I know there can be issues... it's just funny that this is the official disk set. 1 HD disk and 1 DD disk.

I did notice something odd though when I pressed the set up key on the keyboard with the Shard bootdisk in the drive... it reports some sort of large memory expansion. Even though the RAM count shows the normal 640 base and 1024 expanded.

I guess that might be the configuration error my machine complains about, not sure what that is about though.

 

[Krille]

This line of BASIC code will clear the "extended CMOS", i.e. the high half of CMOS (assuming it's 128 bytes);

FOR I%=64TO 127:OUT&H70,I%:OUT&H71,0:NEXT

Might be worth running it in QB or whatever BASIC variant you have available.