Working on an Amiga 1000 - How does one work around the Mezzanine?

[cheshirenoir]

Hey Folks,
So I have recently received an Amiga 1000 (Rev A, PAL with the mezzanine board)
It boots fine to the "insert Kickstart" screen, but if I insert a Kickstart disk (Tried with KS 1.2 and 1.3 on two seperate disks), it gets as far as the reboot, goes black and loses synchronisation.
So I go and grab Chucky's DiagROM and burn the Odd and Even ROMs to a pair of 27C256 EPROMS (Lucky I had some on hand)
Booting off those just gave me a grey screen.
Time to break out the RS232 adapter, and I can see diagnostics information!
Last message is "- Parallel Code $fd - Start of chipmemdetection"
So I am assuming the onboard ChipRAM is bad. (I don't have the 256K expansion plugged in)
How the heck am I supposed to test that RAM with the Mezzanine board in place? Is there a workaround? I don't want to buy a giant box of Dupont leads and make some monstrosity of a connection, but I will if I must.

Happy to hear any suggestions. I'm contemplating just socketing all 8 chips and swapping them one by one for some I have in stock..

Cheers!

Chesh

[Jope]

One thing you could try is to make a 256k rom of diagrom by adjusting rom_base and the test after .yes1114at0 to fc0000, assembling it, then writing it out using WriteKickDisk from Aminet.

Not sure if there are any other direct references to f80000 but it might work.

[cheshirenoir]

I'll be honest, Jope.
I have no idea how to do any of that. :-)

I don't have any HDD Amigas currently so I'm limited to what I can get on ADF. (I have an A600 with an internal Gotek and an external FDD.)

It's been quite a few decades since I last hacked around on Amiga. :-D

Chesh

[Leon Besson]

Have you tried downloading and using Amiga Test Kit on floppy disk?
At least you can test RAM and CIA etc…

https://github.com/keirf/Amiga-Stuff/releases

[cheshirenoir]

Forgive my ignorance, but if the system isn't booting past Kickstart (It never gets to the "insert workbench" screen), this won't work, will it?

DiagROM is indicating that it's starting to test the Chip RAM and then it dies. What I need to know is if there's any way of working on the Chip RAM when it's underneath the mezzanine board.

At this point I'm contemplating two possibilities, neither of which excite me.
1) Socket all the 4464 RAM on the motherboard and swap it out with what I have on hand, possibly in a binary pattern to see if I can find a "dead" RAM chip. Downside: If it's not RAM, and is, instead, the RAM logic, this won't fix it.
2) Turn the board upside down and probe the pins from the underside with the scope. This means a lot of chips are hanging from sockets, it's logistically challenging to work this way and I'm basically working directly on all those pins with nothing to insulate me from the components on the board. Not insurmountable but also not my idea of a "good time".

Cheers!

Chesh

[r.cade]

If there is no raw tool that will test and tell you what RAM is bad, then likely you'll just have to socket it all and test one by one. I would have thought that diagrom would do that, but I suppose it's not THAT low-level. It also could be that it does test that, but your machine doesn't get that far due to a RAM access problem.

[dalek]

you may not be aware of some features of diagrom that can help when the end of your chipram is faulty:

Powerup extras:
press left mousebutton at power on, Screen will be disabled and IF there is fastmem present, fastmem will be used instead of chipmem. Serial console is only option.

if you press right mousebutton at poweron. Computer will use the beginning of detected ramblock instead of end.
(you can combine both buttons at boot)

so try holding right mousebutton and see if you can get diagrom to get along a bit further. If the beginning of chip ram is good then you can run a memtest to try and work out which ram chips could be the issue. I think this will work because you said it boots to kickstart ok.

[cheshirenoir]

Thanks dalek.
I was NOT aware of that. Good to know. Will give it a try :-)

Cheers!

Chesh