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Old 04 October 2019, 12:12   #1
Cav
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Amiga 4000 - strange chipram behaviour

Hi,

I have this A4000 with an odd problem..

A known working (Actually two different) chipmem module, standard jumper settings.
No chipmem in diagrom. Sometimes 1 MB is found ..

If J214 is changed to pin 1-2 (VBB/MA10).
1 MB of chipram is found every time.

If J214 is changed to pin 1-2 (VBB/MA10).
And a 4 MB module is used, 2 MB chipram is found.

What can be wrong...? :/
Also noticed this morning that fastram has siezed to exist
...
CAS/RAS/CRAS/CCAS/BWsignals are checked ok for continuety...
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Old 04 October 2019, 12:20   #2
hooverphonique
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Your jumper setting is the same in both scenarios, is that correct?

Do you have corrosion damage in that area from leaking battery/capacitors?
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Old 04 October 2019, 13:31   #3
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That sounds normal to me, A4000 is picky on modules used for Chip RAM.
Switching jump always forces it to 1MB. What happens if you remove all RAM, you should get Green screen. No green scren means board damage.

For Fast RAM, hooverphonique is correct. Leakage over RAM latch chip with cause that.
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Old 04 October 2019, 13:45   #4
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Quote:
Originally Posted by hooverphonique View Post
Your jumper setting is the same in both scenarios, is that correct?

Do you have corrosion damage in that area from leaking battery/capacitors?


Well.. yes and no..

If I use standard, factory settings.

Sometimes when i boot the machine (with diagrom) it gives me flashing red screen and no chipram. Next day... it MIGHT give the charateristic green flashing and 1 MB found chipram.

IF i change the J214 (VBB/MA10) jumper to none standard setting (jumper between 1-2 instead of VBB to Alice 2-3) I get 1 MB chipram every time.

IF i change the J214 (VBB/MA10) jumper to none standard setting (jumper between 1-2 instead of VBB to Alice 2-3) AND change the SIMM to a 4 MB single sided SIMM i get 2 MB och chipram every time.

So in both the later scenarios the jumper settings is the same. Yes.
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Old 04 October 2019, 13:48   #5
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Quote:
Originally Posted by FOL View Post
That sounds normal to me, A4000 is picky on modules used for Chip RAM.
Switching jump always forces it to 1MB. What happens if you remove all RAM, you should get Green screen. No green scren means board damage.

For Fast RAM, hooverphonique is correct. Leakage over RAM latch chip with cause that.
I'm not sure from the top of my head if I get green screen without chip when running standard ROM.
I'm mainly using DiagROM when fault tracing...

If I remove the chip ram SIMM i do get the same result as I most of the times get when I start it with standard jumper settings.

The SIMMs are known working in my other A4000.



All traces to both chip and fastram sockets are tested ok. ..
Board is cleaned 2, 3 and 4 times... :P
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Old 04 October 2019, 16:32   #6
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Actually, also fastmem is behaving odd...

Memory in first slot, 4 MB
Memory in first and second slot, sometimes 0 MB, sometimes 8 MB.
Memory in first, second and third slot, 4 MB.
Memory in all slots, 0 MB.
Memory in first and third or forth, sometimes 4 MB sometimes 8 MB...........

Haha.. wtf..
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Old 04 October 2019, 17:30   #7
hooverphonique
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Ok.. first, don't mess with J214, it switches between a 2 and an 8 MB Alice, and the latter never existed.

Also, for 2mb chipram you need a double-rank simm, i.e. 2, 8, 32, etc, MB. Use a 2 MB. If you use a single-rank (1MB, 4MB, 16MB, etc), it'll only detect 1 MB of chipram.

Regarding fastram, what size module(s) are you swapping around? If double-rank, only every other slot may be populated.

Last edited by hooverphonique; 04 October 2019 at 17:37. Reason: add comment about single-rank
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Old 04 October 2019, 18:33   #8
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Quote:
Originally Posted by hooverphonique View Post
Ok.. first, don't mess with J214, it switches between a 2 and an 8 MB Alice, and the latter never existed.

Also, for 2mb chipram you need a double-rank simm, i.e. 2, 8, 32, etc, MB. Use a 2 MB. If you use a single-rank (1MB, 4MB, 16MB, etc), it'll only detect 1 MB of chipram.

Regarding fastram, what size module(s) are you swapping around? If double-rank, only every other slot may be populated.
Yeah, i know. But I found this thread online with a guy stating that he successfully used a single sided 4 MB simm and both j214 and j213 flipped giving 2 MB chip. And Guess what, it works.

My other two 2 MB simms are double and works/worked as a charm. Tested in my other A4000.

The fastram aswell is known working, four single sided 4 mb modules.
Everything was working A-OK before my 3660 accelerator went bust.....
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Old 04 October 2019, 18:34   #9
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So there IS something wrong with some component on the motherboard or maybe a trace.
Same behaviour with 3 different working cpu cards.
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Old 05 October 2019, 00:14   #10
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Quote:
Originally Posted by hooverphonique View Post
Ok.. first, don't mess with J214, it switches between a 2 and an 8 MB Alice, and the latter never existed.

Also, for 2mb chipram you need a double-rank simm, i.e. 2, 8, 32, etc, MB. Use a 2 MB. If you use a single-rank (1MB, 4MB, 16MB, etc), it'll only detect 1 MB of chipram.

Regarding fastram, what size module(s) are you swapping around? If double-rank, only every other slot may be populated.

What he ^ says. Don't screw with it. With a working 8MB SIMM you don't have to do anything but plug it in. Ignore that post you're talking about, where the guy goes, "I'm out of 2MB SIMMs, I'll just put an 8MB one in and set this jumper", and yes you can set the jumpers incorrectly and it still *might* work, but just set them as the manual states.
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Old 05 October 2019, 08:02   #11
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Originally Posted by grelbfarlk View Post
What he ^ says. Don't screw with it. With a working 8MB SIMM you don't have to do anything but plug it in. Ignore that post you're talking about, where the guy goes, "I'm out of 2MB SIMMs, I'll just put an 8MB one in and set this jumper", and yes you can set the jumpers incorrectly and it still *might* work, but just set them as the manual states.
Well, of course I would have used my original SIMM if there was no errors on the motherboard, that is also my intention..

But as it is now, it doesnt work. Thats why I would like some help of you experienced guys. And to get a little guide in WHY Alice finds 2 MB of ram if I flip the jumper and just 1 MB in original state...
The jumper just connects Alice DRA10, with U213 I9 and U212 I_CK.

I know that the jumper setting is wrong, no need to point that out.
I wouldnt just change it for fun. But Im very interested in why it makes it work 'a little better'....

Maybe I'll have to be more clear about that it isnt working, and that im trying to get it to work. Its not a weekend joy to drink beer and change jumper settings.

None the less, other hints are welcome.

Last edited by Cav; 05 October 2019 at 08:08.
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Old 05 October 2019, 10:23   #12
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Quote:
Originally Posted by grelbfarlk
What he ^ says. Don't screw with it. With a working 8MB SIMM you don't have to do anything but plug it in. Ignore that post you're talking about, where the guy goes, "I'm out of 2MB SIMMs, I'll just put an 8MB one in and set this jumper", and yes you can set the jumpers incorrectly and it still *might* work, but just set them as the manual states.
I don't know where you got the "8MB one" but with a 4MB SIMM you get a fully working 2MB chip RAM when the jumper J213 is set to 8M and J214 to 8M.
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Old 05 October 2019, 11:35   #13
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Thumbs up

Quote:
Originally Posted by hese View Post
I don't know where you got the "8MB one" but with a 4MB SIMM you get a fully working 2MB chip RAM when the jumper J213 is set to 8M and J214 to 8M.
Thanks for verifying Hese.
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Old 05 October 2019, 20:47   #14
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I don't know where you got the "8MB one" but with a 4MB SIMM you get a fully working 2MB chip RAM when the jumper J213 is set to 8M and J214 to 8M.
Ok, then I was wrong.
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Old 05 October 2019, 21:04   #15
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Ok, then I was wrong.

I think its pretty cool that there is a way to use 4 MB SIMMS though...

But still... I would like to find the reason for why it doesnt work as its intended...
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Old 06 October 2019, 08:31   #16
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From Wikipedia..

†/RAS1 and /RAS3 are only used on two-rank SIMMS: 2, 8, 32, and 128 MB.

https://en.wikipedia.org/wiki/SIMM


Does it makes sense that I have an issue with RAS1 & 3 as it works ok a larger single sided simm?
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Old 13 October 2019, 09:55   #17
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First issue solved.
Change of U891 and reflow of U212.

2 MB chipram and 16 MB fastram consequent.

Now its only the graphic issue left.... :/
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Old 14 October 2019, 04:46   #18
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Quote:
Originally Posted by Cav View Post
Actually, also fastmem is behaving odd...

Memory in first slot, 4 MB
Memory in first and second slot, sometimes 0 MB, sometimes 8 MB.
Memory in first, second and third slot, 4 MB.
Memory in all slots, 0 MB.
Memory in first and third or forth, sometimes 4 MB sometimes 8 MB...........

Haha.. wtf..

Sounds like some of the connections in the SIMM slot isn't making proper contact. IIRC the 4000 needs to see the previous slot before looking at the next one. So if it doesn't see memory in the 2nd slot, it won't look at the 3rd one.



I had a broken part in my 2nd slot which was preventing the memory from being seated properly, so I had to put some non conductive inserts between the memory to get it to recognise properly. I've got to replace the slot itself one day!
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