modem7
10k Member
So, a type 1 motherboard, and you have upgraded the motherboard BIOS to the final revision.
Do you recall experiencing the symptom before that upgrade ?
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Ibm pc at parity check
- Thread starter jacobtohahn
- Start date
Do you recall experiencing the symptom before that upgrade ?
jacobtohahn
Experienced Member
Still works now
. Any software that I can use to occasionally backup the drive to a folder on the 100MB HardCard (D drive) just in case?Hoping that’s not what it is!! These cards are pretty rare and expensive. If that is the issue I’d have to change to a RAMpage AT.
I’ll reseat the chips after running CheckIt.
jacobtohahn
Experienced Member
Not sure. I still have the old ROMs so I could try the old bios again. If that’s the issue then I don’t know how I’d use the 2.5” drive I installed afterwards. Probably using a 3rd party bios.
modem7
10k Member
If so, you have the option of running the card with its parity checking turned off. Not nice, but still an option.
It would be good to rule the BIOS upgrade out of the 'possible cause' list.
modem7
10k Member
modem7 said:
If that changes, a burial at sea will be very appropriate.Still works now
jacobtohahn
Experienced Member
Haha, I actually have 2 of those hard drives and both work fine.
jacobtohahn
Experienced Member
SOLVED! It was the BIOS. I replaced it with the AMI BIOS and it works like a charm.
jacobtohahn
Experienced Member
And no, nevermind then. After a few hours of operation it did the exact same thing. I think that I should turn off parity checking.
modem7
10k Member
If the parity generation/checking circuitry is working properly, then there is a RAM related problem. If so, the symptom may simply change to 'DOS just locked up' or 'My running program just locked up'.
The RAM test done by the power-on self test is rudimentary - just a confidence thing. How did the running of the RAM test in CheckIt go ?
jacobtohahn
Experienced Member
The CheckIt test passed completely fine. I’ll test without parity checking and see if DOS locks up.
EDIT: Still happening even without Parity checking enabled.
EDIT 2: I’m almost sure it’s the card. I’m going to buy a RAMPage AT and use it instead.
EDIT 3: After even more testing, I’ve found that it is actually the onboard RAM itself. I have a spare 5170 board that I swapped the RAM from. Testing now.
EDIT 4: Still getting it even with new RAM. That narrows it down to the motherboard parity circuitry. I will swap out the entire board tomorrow. The board is untested but seemingly working.
Also, here’s a picture of the screen with the error:
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jacobtohahn
Experienced Member
I swapped out the system board and it seems to be working fine, however it only detects 2048K when it counts instead of the usual 2560K. Any ideas why? It’s not too much of an issue but I’d prefer to have that little bit of extra RAM.
EDIT: Even with new RAM, a new motherboard, new ROMs, and only the essential cards required for running the PC, the error still occurs. Is this even possible? Could it be the FDD controller? The processor? One of the drives somehow? This is basically a new computer now. I could get a new 80286 off of eBay if I need to, but is it even possible that that is the issue? I’m pretty sure that it could possibly be the hard drive. I have another CMI 6426 that I could test with, but it doesn’t have any software and drivers I need. If that’s the issue I could do that painstakingly slow process of moving files by floppy disk.
EDIT: Even with new RAM, a new motherboard, new ROMs, and only the essential cards required for running the PC, the error still occurs. Is this even possible? Could it be the FDD controller? The processor? One of the drives somehow? This is basically a new computer now. I could get a new 80286 off of eBay if I need to, but is it even possible that that is the issue? I’m pretty sure that it could possibly be the hard drive. I have another CMI 6426 that I could test with, but it doesn’t have any software and drivers I need. If that’s the issue I could do that painstakingly slow process of moving files by floppy disk.
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modem7
10k Member
* Maybe I missed it, but I cannot see anything in the previous threads where a different power supply was tried.
* Flakey house power !
* Air conditioner kicking in and out !
diskettenfett
Member
- Joined
- Feb 8, 2014
- Messages
- 19
Hi
I'd bet that you don't have a hardware fault, but instead your PC is haunted by a very common boot sector virus, which will at seemingly random intervals display the message PARITY CHECK in 40 column mode and hang the machine. It is called Parity Boot, was very common in the early to mid 90s. As it is a boot sector virus, it spreads to any floppy accessed by the infected machine. I got Parity Boot multiple times, back then we used F-PROT to detect it. Removal is simple, just boot from a known clean floppy and rewrite the MBR of the hard disk with the command FDISK /MBR. Floppies can be cleaned with F-PROT.
I'd bet that you don't have a hardware fault, but instead your PC is haunted by a very common boot sector virus, which will at seemingly random intervals display the message PARITY CHECK in 40 column mode and hang the machine. It is called Parity Boot, was very common in the early to mid 90s. As it is a boot sector virus, it spreads to any floppy accessed by the infected machine. I got Parity Boot multiple times, back then we used F-PROT to detect it. Removal is simple, just boot from a known clean floppy and rewrite the MBR of the hard disk with the command FDISK /MBR. Floppies can be cleaned with F-PROT.
diskettenfett
Member
- Joined
- Feb 8, 2014
- Messages
- 19
Remember to scan and disinfect all the floppies you ever inserted into this machine, and other machines you used these floppies in. The Parity Boot virus will stick to you like glue, trust me... I still found infected floppies decades after having the first Parity Boot infection.
For a quick test: Boot the machine from a known clean and write protected DOS boot floppy. You shouldn't receive the PARITY CHECK message anymore. You could even take a look at the boot sector of the hard disk with Norton Disk Editor while working from a clean boot floppy and see the virus itself. Probably won't work when the computer is booted from an infected medium - if I remember correctly, the virus will hide any changes to the bootsector and just deliver an intact original boot sector when it is active.
For a quick test: Boot the machine from a known clean and write protected DOS boot floppy. You shouldn't receive the PARITY CHECK message anymore. You could even take a look at the boot sector of the hard disk with Norton Disk Editor while working from a clean boot floppy and see the virus itself. Probably won't work when the computer is booted from an infected medium - if I remember correctly, the virus will hide any changes to the bootsector and just deliver an intact original boot sector when it is active.
jacobtohahn
Experienced Member
I have an extra UPS that I can try. The power here usually seems fine though. Also, about the motherboard only detecting 2048K, is there a solution to that? I would like to avoid swapping the motherboard, as doing so increases the chances of me damaging the RAM chips or the board itself. Also, I believe that this board is newer because the chips are dated later and the board looks cleaner. The old board’s PCB is orangeish-brown (not from corrosion) while the newer one is green.
I’ll definitely try that on Monday, traveling this weekend. Pretty sure that is the issue, as the symptoms sound exactly like what I have.
modem7
10k Member
It would certainly explain the lack of 'PARITY CHECK 1' or 'PARITY CHECK 2'.
I have never encountered the subject virus before. Why didn't they make it more convincing by displaying, 'PARITY CHECK 1'.
modem7
10k Member
No error message from the POST ?
jacobtohahn
Experienced Member
None at all. It says I have 640KB of base memory (obviously backfilled) and 1408KB of expansion memory. In reality, I have 640KB base (backfilled) and 1920KB expansion.
modem7
10k Member
Looking at post #4, the expected RAM configuration is 640 KB of base memory and 1920 KB of expansion (not expanded) (extended) memory, per the diagram at [here].
And therefore, you will have configured SETUP for 640 KB of base memory and 1920 KB of expansion memory.
Or are you making an assumption ?
And therefore, you will have configured SETUP for 640 KB of base memory and 1920 KB of expansion memory.
But the POST does not break its RAM count-up figures into base and expansion; it just has the one count.
Or are you making an assumption ?
modem7
10k Member
With the CheckIt diagnostics tool, one can specify a range of RAM addresses to test. With that, you should be able to prove that your AST RAMpage 286 is now providing 512 KB less RAM, and where in the 5170's address space the loss is occurring at.
Then, the question becomes, why the loss. Maybe try toggling the AST RAMpage 286's switches in case there is a bad contact in them. Maybe try re-seating all of the card's RAM chips.
Then, the question becomes, why the loss. Maybe try toggling the AST RAMpage 286's switches in case there is a bad contact in them. Maybe try re-seating all of the card's RAM chips.