A2000 Rev. 6 GREEN!!!!

[curtis]

Okay, finally got around to working on the 2000 I bought on fleabay a while back which had MASSIVE battery damage.  Only thing I saved from that board were a few custom chips that were WAY far away from the battery.  CPU was really bad.

Anyway, picked up a new motherboard (Rev. 6) from a fellow here (not going to name names since it's been several months since I got it) but when I fire it up, I get the dreaded green memory bad screen.

Tried swapping ALL the socketed chips with known good ones from a spare A500 mobo I have.

Nothing changed.

Left it on for a bit to check for a hotter than normal chip.  Nothing.

Tried the piggy-back RAM chips - nada.

Only thing different is the RAM chips on the 2000 motherboard are 64258-10.  I know the speed is 100ns (-10), but what is the 64258?  I've tried 64256 and 514256.  Both have no effect on the problem.

I'm assuming the 64258 and the 64256 SHOULD be compatible, but tried searching on the web and couldn't find anything on the 64258's.

Suggestions and information would be greatly appreciated.

Curtis

[arttu80]

Hi!

Bad luck with A2000s, huh? I once bought 2x Rev.4.4 B2000 machines, which were used in school from day one, so no one cared to check em. Both had very bad acid damages, managed to rescue one mobo with some jumper wires soldered and cpu + rom socket replaced.
But anyway, have you checked which Agnus version your mobo has and how it's RAM is configured? I mean these J101 and J500 ones? If you have Agnus P/N:8371 (PAL machine 512 Chip RAM version) and your motherboard configured to use extra 512k as Chip, it won't work. This was my "two cents" on your problem. Hope will work out well!

[amiman99]

Check this out, hope it helps...
http://home.arcor.de/kickstart/TKA/Tutorials/troubleshooter/trouble1.html

[magnetic]

Hey Curtis
Thanks for being so nice. (he got it from me) the board was a working pull from a spare a2k. I pm'd u this link : http://home.arcor.de/kickstart/TKA/Tutorials/troubleshooter/trouble2.html

Let me know if I can help we will get it solved.

[curtis]

Already tried swapping out Agnus.  Tried a couple of 8372a's, and 8370's.  No joy.

Thought it might have been configured for a minimegi.  Nope.

Starting to smell like a RAM chip suicided, but now to figure out which one!

[curtis]

Oh, btw, the only RAM in it is the stock 512K.

Basically, I'm starting from square one.  No expansion boards.  Just the power supply and the motherboard.

Still waiting for an answer on the RAM chips.

[magnetic]

I think i have another rev 4.4 2000mb here I could send u, but it has a trace cut (for megachip iirc) that would need to be soldered.. lets see how this goes though that board should work ok.

Are the onboard ram chips getting hot?

[curtis]

None of the RAM chips are getting hot.

As far as the megachip, I happen to have a spare I was thinking about popping into the A2000.  Just wanted to verify my base before I started building if you know what I mean.

Just to let everybody know.

I AM NOT BLAMING MAGNETIC ON THIS!  Something could've happened in transit, or, with electronics this old, something just died.  It happens!  Unfortunate, but true.

@magnetic:  Let me do some more tinkering on this motherboard, but I may get back to you on the 4.4.

Could someone PLEASE verify the chips for me!  I'm fairly handy with a soldering iron, but wouldn't want to put the wrong chips in as replacement!  Even using sockets, replacing once is enough.

Curtis

[curtis]

SUCCESS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Got out my magnifying bench light and looked VERY closely into the Agnus socket(my x-ray vision is on the fritz right now.  Wish I could find where the wife has hidden that $#@%^ green kryptonite!).

Found a couple of very small metal fragments that had dropped into the socket and were shorting a couple of pins.

Removed those and it booted right up!

Now to get back on track of building this beauty up.

I appreciate all the help that was offered.

Curtis

p.s.  Would still like to confirm those RAM chips are equivalent.

[spirantho]

Well done! Glad you got it working!

The A2000 doesn't like mixed type of RAM within its bank, and you'd be mixing Static Column RAM with Page Mode RAM.

http://www.amiga-stuff.com/hardware/256kx4-dram.html

[magnetic]

Curtis

Great! Glad to hear it! I was puzzled when  you said it greenscreened after you checked agnus as ok

Anyway thanks for being so cool about it. Trust me, from years of selling to amiga people, some guys go bannanas right away, and I dont mean the dancing kind.  (magnetic is a crook! that thief! LOL)

[curtis]

The reason I said the Agnus was okay was because I checked it in a known good motherboard.  Based on the other board firing right up, most people would ASSUME the socket was also good.  


And what happens .when you assume?

[mongo]

Well done! Glad you got it working!

The A2000 doesn't like mixed type of RAM within its bank, and you'd be mixing Static Column RAM with Page Mode RAM.

http://www.amiga-stuff.com/hardware/256kx4-dram.html

An A2000 doesn't care. Agnus always accesses RAM in the same way. It doesn't matter which type you use because it doesn't use the special features of Static Column RAM.

[curtis]

So, would it be safe to say the 64258 is a static column type RAM?

Just trying to understand what the differences are.

[spirantho]

I'd still never recommend mixing them, though. Certainly in my A2000, if I mix working RAM chips of a different type (all Page Mode, though) within a bank, it just green screens. It's doubly important if you're trying to fix a non-working board that you use a known working combination.