Possible DRAM issue with my Osborne 1a, looking for specific cause and fix

[BushmanBushman]

I have been experimenting with my Osborne 1a and trying to see if it will work with a gotek without success, and I noticed some failures and errors that may be related to the DRAM, although I am uncertain. These errors only occurred after attempting to boot from the gotek, and letting it run for a little while. They are inconsistent, and I have not been able to reproduce specific symptoms more than once. If anyone is familiar with the Osborne, and might be able to suggest what might be failing and any possible fixes, it will be greatly appreciated.

 

[cj7hawk]

I suspect at this point, the only two actions to take next would be;

* Socket the RAM and replace and test or;
* Write test code to sit inside the boot ROM and test system memory.

Neither is a simple task.

 

[ldkraemer]

My first step would be go back to the two Floppy system, then try booting from A AND then B.
One of the floppy drives should boot from Floppy. Then you can run some diagnostics to
test RAM etc.


Larry

 

[cj7hawk]

@ldkraemer , He's already tried booting from Floppy Drives, as well with a gotek, and both with and without the DD adapter attached.

In all cases, except single density disk with the DD adapter, the system starts to boot then fails ( as in the Gotek reports that it's being accessed ).

Hence I am thinking something is getting in the way of the code executing properly. Ram corruption would be a likely contender, but not the only possibility.

 

[ldkraemer]

That might be, but he states "These errors only occurred after attempting to boot from the gotek, and letting
it run for a little while".

Larry

 

[cj7hawk]

@ldkraemer , yes, the full information wasn't included in the post so I added some extra that I knew of.

I'll add a little extra that he provided earlier in case it assists, as you might make more of what he previously mentioned to me. I don't think he'll mind me posting the technical elements. I did mention trying both drives.

The boot disks that came with the computer didn’t work in either drive, same bad sector error. The weird thing is that only the DD disk files didnt produce an error, while the SD disks, physical and digital produced bad sector errors, which is why I went down the gotek route to begin with. I’m also questioning why even though my computer has the DD adapter but came with SD OS disks.

and when I mentioned it might be the ram he added;

My only thought is that if it was a ram error, I don't know why these issues wouldn't be evident from boot. They only made themselves apparent after loading a "disk" and I only started seeing them, though I could have just not waited long enough to notice them, after removing the double density board, testing it without, and putting it back together. The issues also are not consistent, and don't happen every time I load a "disk". Each of the screenshots I sent are errors that only occurred once for me. Although I didn't get a photograph of it, during one of the failures, the screen filled up with half blocks and the number 5, before it restarted itself. I'll certainly start testing the rails once I have the chance to.

I'm not certain it's a memory fault, but it's not booting regardless. It's uncertain as to whether his original floppy boot disks were faulty.

If this brings up any other ideas, I'm sure your input will be appreciated - He did mention to me he will be away for a little while, so may not get back to the forum for a week or so.