Sad Amiga - Possible memory issues?

[camsoft2000]

Hi all,

So I recently bought an Amiga 500 and have been experiencing issues with most software.

My system:
Amiga 500 rev5 (in a 500Plus case)




I’ve performed the following hardware upgrades:

- Upgraded Agnus from 8371 to 8372A and covered the NTSC/Pal switching PIN.
- Upgraded KickStart 1.2 with 3.x ROM and used a ROM adaptor to allow EPROM ROM on rev5 board.
- Installed a disk switcher to switch between external and internal boot drives
- Modded and installed a Gotek installed externally
- Installed Boobip 2MB memory expansion board into the trapdoor.
- Installed Boobip Gary adaptor for above memory expansion to utilise more than 512k
- Performed chip RAM mod (JP2) to utilise chip and slow RAM at same time.

According to Amiga Test Kit I’ve got as expected 2.5MB (Chip 1MB — Fast 0.0MB — Slow 1.5MB).

What I’m seeing is sporadic red guru style crashes see below:




I’ve looked up the Guru message reference but these errors don’t appear to match the format I’ve seen posted on the web.

I get these crashes pretty much with most software either when loading or when loaded and just using games and software.

I’ve seeing these crashes with:
- Workbench 3.1
- Lemmings
- Pinball Fantasies
And other games software.

The occurrence of the crashes are varied and won’t always crash at the same point.

Also crashes are much more frequent using the memory upgrades mentioned above.

On removing all the memory upgrades and expansion board software like Workbench will load much further and actually fully load but then crash when using a little later. So the issues seem amplified when adding the additional memory but they don’t appear to be exclusive of having the expanded memory installed.



I’ve ran a memory test for a good 10 minutes and no errors are reported.

What’s puzzling is I’m getting guru style software errors and not hardware errors yet I’m pretty certain it’s a hardware issue and the fact that errors are more frequent when using the memory upgrades seems to confirm that.

I’ve checked all the chips and seated them all. There is some corrosion on some of the pins but I assume if they didn’t work I wouldn’t even be able to load software and would get a coloured screen.



In installing the memory upgrades I followed the instructions on Boobip exactly http://www.boobip.com/hardware/A500_2MB

Though as I say I don’t think that’s the issue as it still happens when all the upgrades to memory are reversed.

I’m still running the AmigaTestKit memory check now and it’s on round 60 currently with zero errors.

Help would be greatly appreciated. Thanks!

[camsoft2000]

Here is a video, I’ve trimmed the first 30 or so seconds of it loading Workbench. Also I click continue when getting the errors messages.

https://share.icloud.com/photos/0K5w...hX9lDA2fvpo5Qg

It is pretty much guaranteed not to load and show errors like this with the expansion memory board, without the upgrades installed it does load to the desktop and can be used for a number of seconds before it will still crash.

[camsoft2000]

Here’s another video loading lemmings, it crash before even started to load a couple of times and then it just loaded all the way the title screen:


https://share.icloud.com/photos/0xaH...gg#Woodingdean

[camsoft2000]

Just tried putting the original Kickstart 1.2 ROM in and loading Workbench 1.2 but no luck.

[cmorley]

If the crashes happen without the RAM expansion then I'd suggest a closer look at the CPU and Agnus sockets. Contact cleaner, check for contacts which are broken or have lost their springyness and clean any tarnished pins on the ICs with a fibre glass pencil.

I'd do that before looking closer at the memory data buffers etc.

BTW to avoid removing and reinserting the Gary adapter multiple times (which won't do the Gary socket any favours) while you do tests you can bypass it and leave it installed.
Simply use 2 jumpers & link pin 5&6 and 7&8 on the Gary adapter 8 pin connector.

[Lord Aga]

Sharp TVeeeee

What model is it?

[22dave66]

Did you swap the to old Agnus when you removed upgrades?

Like @cmorley said, removing and reinserting chips doesn't do the sockets any favours, the Agnus socket isn't as robust as it looks. I would flip the board over and check for dry joints and any damaged solder pads. Might be worth changing the sockets where you have fitted the upgrades or even re-solder them in place (quick repair for countless A500's in the past).

[camsoft2000]

Originally Posted by cmorley

If the crashes happen without the RAM expansion then I'd suggest a closer look at the CPU and Agnus sockets. Contact cleaner, check for contacts which are broken or have lost their springyness and clean any tarnished pins on the ICs with a fibre glass pencil.

I'd do that before looking closer at the memory data buffers etc.

BTW to avoid removing and reinserting the Gary adapter multiple times (which won't do the Gary socket any favours) while you do tests you can bypass it and leave it installed.
Simply use 2 jumpers & link pin 5&6 and 7&8 on the Gary adapter 8 pin connector.

Hi Chris,

Thanks for the advice, I did removed the Gary adaptor but I'll use jumpers to bypass if I need to do so again.

What I find puzzling is that the issues are massively amplified when using the memory upgrade.

It will pretty much load nothing with it installed, though AmigaTestKit always works fine and doesn't crash also a very smaller games seem ok.

When removed and when restoring the JP2 jumper I can load things and get much much further, but it will still occasionally crash.

I don't understand what is going on here why would extra memory exaggerate the issue?

One thing I did notice when I removed the Gary chip pin 27 was bent up (see below) and I don't know if this was done on purpose or not, but I straightened that pin, also pin 25 broke, so I had to repair that.

[camsoft2000]

Originally Posted by Lord Aga

Sharp TVeeeee

What model is it?

Ha, that's a SHARP LC-20SH1E 20" which I got of eBay, works a treat.

[Fastdruid]

8000 0004 is Illegal instruction. As actually is an 0000 0004, only the 0000 0004 is recoverable.

https://wiki.amigaos.net/wiki/Unders..._error_numbers

[camsoft2000]

Originally Posted by 22dave66

Did you swap the to old Agnus when you removed upgrades?

Like @cmorley said, removing and reinserting chips doesn't do the sockets any favours, the Agnus socket isn't as robust as it looks. I would flip the board over and check for dry joints and any damaged solder pads. Might be worth changing the sockets where you have fitted the upgrades or even re-solder them in place (quick repair for countless A500's in the past).

I did remove the Agnus with a PLCC extractor, the solder joints look good actually, I had the board out for a clean yesterday, sockets look good to, though chip pins look less healthy.

[camsoft2000]

I’m going to take another look at the board and maybe resolder the sockets, also going to clean the pins on the chips as Chris suggested.

[camsoft2000]

So I’ve taken the board out and the chips that I had upgraded so I can prepare and clean the contacts and chip pins.







Looks pretty good to me, just wondering if it’s worth resoldering. I’m going to use the continuity test on my multimeter to make sure the sockets are good.

[camsoft2000]

There is little bit of mess near the sockets not sure what that is.

[cmorley]

There could be a number of reasons why adding an expansion makes crashing worse.

If power is a bit flakey then increased load might make something marginal that little bit worse (P.S. have you checked the 5v rails at the RAM chips and RAM buffers?)

If a logic chip is on its way out then driving more load might make it worse.

More RAM moves code into slow RAM to save chip RAM. Whatever the flaky thing between the CPU and RAM is might be slightly worse with the RAM on the expansion.

Poor connection on the 68000 gives all sorts of problems from yellow screen to crashing Workbench. Intermittent too. This is why wiggling the CPU often fixes problems for a while - you slightly improve the contact (for a short time). Cleaning chips and cleaning/replacing sockets cures a lot of faults.

[camsoft2000]

Originally Posted by cmorley

There could be a number of reasons why adding an expansion makes crashing worse.

If power is a bit flakey then increased load might make something marginal that little bit worse (P.S. have you checked the 5v rails at the RAM chips and RAM buffers?)

If a logic chip is on its way out then driving more load might make it worse.

More RAM moves code into slow RAM to save chip RAM. Whatever the flaky thing between the CPU and RAM is might be slightly worse with the RAM on the expansion.

Poor connection on the 68000 gives all sorts of problems from yellow screen to crashing Workbench. Intermittent too. This is why wiggling the CPU often fixes problems for a while - you slightly improve the contact (for a short time). Cleaning chips and cleaning/replacing sockets cures a lot of faults.

That's really helpful advice.

Btw I'm in no way suggesting the memory expansion card is the issue, I was just trying to understand how it would amplify the issues I was having to help diagnose where the problem lies.

Do you have any information or links that would help me with testing the voltages on the RAM chips etc?

Thanks!

[cmorley]

The schematics for Amigas are online. Google "A500 rev5 schematic PDF" for example. Datasheets for the parts have the pinouts of the ICs.

[jolly11]

"So I recently bought an Amiga 500 and have been experiencing issues with most software"

are you sure it worked fine before the upgrades?

[indigolemon]

Have a read of this: https://retrohax.net/amiga-500-mods-2/

Specifically - one of the machines Drygol deals with he has to adjust pins on the Agnus to deal with symptoms that sound very like yours.

[camsoft2000]

Originally Posted by jolly11

"So I recently bought an Amiga 500 and have been experiencing issues with most software"

are you sure it worked fine before the upgrades?

Well I couldn’t do much with 512K but yeah Workbench 1.2 was loading and never saw a crash.