I've been looking at a friends 386 which they claimed had hard drive problems. I've swapped the hard disk over -removing the FDD cable in the process. Upon initial bootup I get 'CMOS Checksum error' and hit <F1> to enter.

I select 'Hard Drive Auto Detection' and it finds my hard drive. I also select 'Reset to default settings' to restore the CMOS values. Following this I power off the computer insert the FDD cable so I could use the disk drive and power the machine back on.

I get two short beeps (POST ERROR) and then three beeps (Base 64K RAM fail) followed by two more beeps (parity error). It now reports 'CMOS Memory Size Error' and then asks to 'press <F1> to enter setup'. Upon pressing F1 to get back into the BIOS

ON BOARD PARITY ERROR
Addr (HEX) 0000:0002
SYSTEM HALTED

The M/B is an ISA386 (taiwan) with 4 x 1MB 30PIN SIMM RAM (with two chips on each which I think is nonparity). I have tried reseating the memory chips as well as swapping their positions in bank 0 on the M/B. The BIOS is an AMI 1992 386DX but I cannot get into the setup anymore because the parity error always comes up even pressing <F1> to bypass or holding <INS> doesn't work

On the PC Chips site they state that the most common cause of this error is BIOS configuration rather than faulty memory - especially if the reported address is the same (which is true and the system was working before this). I suspect that maybe returning BIOS to system defaults caused parity error checking to be turned on and now I can't turn it off.

I then thought of resetting the BIOS and found the Nicad battery was leaking (causing the initial problem with checksum error) and have since removed this from the motherboard. I have removed the BIOS/CMOS chips and shorted their legs out hoping to erase the contents and then replaced them but still the same problem.

I am thinking that I might have to chase down some parity 30pin SIMM RAM now. Does anyone think that removing/replacing FDD cable on IDE controller card caused the problem with the memory? Has anyone any suggestions?

Thanks
Matt

On Some older bios
You can tap the DEL(or what ever key your bios requires) during boot up to get into the Bios
In a Few older systems you can also Press and hold down the 0 (Zero key) during boot to clear the cmos.

In all the old systems I have worked on shorting the posts on the cmos to clear them the chip had to be installed in the M/B for the short to work.

Adding the cable should not cause this problem.
The bios checking the memory for parity is the cause.
Another way to clear the cmos that has worked in the past was to remove the Batt. Then unplug the Power supply and let the unit sit for a period of time.
Reboot later without the Batt installed.
You should get a check sum error and enter setup

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To ERR is HUMAN
To REALLY screw things UP, YOU NEED a COMPUTER !

Thanks for the quick response.

I've tried hitting <DEL> to get in the BIOS and the parity error message came up straight away. I actually took the CMOS chip out also prior to posting and shorted the pins with a screwdriver but that didn't work either. Also had unsoldered and removed the Nicad at the very beginning because it was leaking.

Your last suggestion was spot on. Obviously though the power wasn't drained enough because I left the computer alone for about 2 hours and powered it back on the error has disappeared and is replaced with 'CMOS battery low'.

Thanks
Matt

It is also possible that since the battery was leaking that corrosion is now a problem. Try cleaning the battery area, with a mild acid solution (vinegar mixed with an equal amount of water), rinse well and let dry completely before plugging in and returning any power....


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mjc
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Celts are the men that heaven made mad, For all their battles are merry and their songs are all sad.