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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: pentivarg on June 23, 2024, 10:22:48 AM
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Hi,
I wonder if anyone has an idea of what hardware error can generate this error message (please see attached image). And where on the motherboard I should do more thorough checks.
I have several ram-modules, all 4 MB 70 ns. The jumper on the motherboard is set at 4 MB modules.
It doesn’t matter which module I use, or in which slot I put them, I still get the same error as in the image. If I change slot the only thing that change is the address range tested.
I’m using DiagROM v1.3. The CPU is a 68040 on a A3640 rev 3.1 board. The A4000 motherboard is rev B.
I would be most grateful for any input that can help narrowing this down to something that can be fixed 😊
Stefan
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Has the mainboard been recapped? Battery removed? Any battery leakage still on the board? Could be a trace damage.
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I should have mentioned that. It has recently been recapped. The battery has been replaced by a new one. The area around the battery looks quite good. Nothing visual that looks wrong. I don't think the old battery leaked. I have another rev B MB which had some serious battery leakage so I know how that looks like.
But yes, it could still be a small trace damage somewhere. The question is in which area of the MB to start looking.
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Start by checking there is address bus data on all 32 lines at U890 (Ramsey).
At any one of the fast memory SIMM sockets, check there is multiplexed address data (row/column) on all 10 of the fast RAM address lines. There should always be activity on these lines due to the constant refresh cycles, regardless of any system activity. Looking at the signals with a 1uSec/division timebase, you should see something like 4 active low strobes on each line.
Would also be worth checking that all 4 column address strobes at the SIMM sockets have activity. Those 4 signals are common to each SIMM socket, so doesn't matter which socket you check.
Could also be a defective U890, though it wouldn't be my first guess.
What behaviour do you see when running the system normally, with standard ROMs? Are you seeing something like it running OK with chip memory only, but you get some kind of failure (e.g. yellow screen) when trying to boot with any fast memory fitted? If you try to boot with no startup and report the system memory (using 'avail'), do you see the correct amount of fast memory reported, even if it isn't usable?
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Thank you for your very detailed instructions :) I do have a PicoScope 5243D MSO but to be honest I have never used it :( I'm a semi-noob at this but I got a genuine interest to learn how to triage at that level.
If I only have chipram installed everything is fine. It boots up and the diagrom happily runs the chipram tests, including address error checks.
If I boot from normal kickstart with fastram installed the power led blinks and the screen stays black. I'm using a RGB to HDMI converter so the colors are not accurate and it lags a bit when the input signal comes and goes.
It's only when I use diagrom that I can get it to boot with fastram installed.
Are there any other tests I can run to narrow it down before bringing out the big guns (the oscilloscope) which I'm not 100% sure how to use yet... Haha
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If I only have chipram installed everything is fine. It boots up and the diagrom happily runs the chipram tests, including address error checks.
If I boot from normal kickstart with fastram installed the power led blinks and the screen stays black.
That's what I'd expect with an address error, so DiagROM has picked up the error correctly. The standard ROM only does a quick write+read test, which passes in this case, then adds the detected memory to the system. When the system tries using the memory, it fails catastrophically due to the address problem as it ends up with data for one address overwriting a different address.
Are there any other tests I can run to narrow it down before bringing out the big guns (the oscilloscope) which I'm not 100% sure how to use yet... Haha
Not really. And unless you have months of time to waste, I'd not recommend the shotgun approach of 'replacing every component until it works'. You really need to know what you're looking for with a fault like this, it's not a great 'my first oscilloscope' job. You might like to give it a try, there's a fairly low risk of damaging something. The trickiest bit is the fact that half of the important things you need to measure (at U890) is underneath the CPU board, making physical access difficult.
Another option is to send the board to me in NZ for repair. I'd suggest checking freight prices first, international freight prices have quadrupled in recent years. The shipping weight of the A4000D main board is around 1.3kg. The shipping carton size would typically be around 30 x 40 x 10cm.
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Since you're using DiagROM v1.3 and have a setup with an A3640 rev 3.1 board and A4000 rev B motherboard, focusing on the address range tested might be key. Have you checked the CPU socket and surrounding circuitry?
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I had an issue with Fastram not being recognised. I replaced Buster and it resolved the issue. Check around the SIMM sockets for corrossion. Battery damage can extend under the SIMM sockets and you dont see it until you remove them.
Try swapping the SIMMS around. Start with one in the first slot, then try it in the seocnd and so on for third and fourth and see what Diagrom reports after each run. May help you narrow it down if tis a problem with a SIMM socket.
Weed
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I have run the diagrom address range test which is what is shown in the screenshot in the first message. I have also moved around the simms between the sockets with the same results.
But I have not tested to replace the super buster. I have one on another motherboard so I can try using that one and see if I get different result.
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Thats how I identifed the problem with Buster. I swapped it with a -07 version from my A3000D (the A4000 was -09); the -07 doesnt work properly in the A4000D but it did highlight the issue. I ordered a -11 part from Analogic. Price of Busters has since shot up - I got mine for I think less than £100, Analogic now selling them for c£150.
Chip Name Part Number Used in
Buster 5721 318075-01 A2000
Buster 5731 Rev A 318075-02 A2000
Super Buster 71 390529-06 A3000
Super Buster 45 390537-09 A4000
Super Buster 71 390539-07 A3000
Super Buster 45 390539-09 A3000, A2631
Super Buster 45 390539-11 A4000, A4000T
From Big Book of Amiga Hardware: https://bigbookofamigahardware.com/bboah/product.aspx?id=1484#:~:text=Though%20you%20think%20it%27s%20the%20same%20chip%2C%20there,it%20does%20NOT%20support%20Zorro%20III%20bus%20masters. (https://bigbookofamigahardware.com/bboah/product.aspx?id=1484#:~:text=Though%20you%20think%20it%27s%20the%20same%20chip%2C%20there,it%20does%20NOT%20support%20Zorro%20III%20bus%20masters.)
https://www.analogic.co.uk/shop/amiga/a4000/shop-amiga-a4000-chips-and-roms-html.html (https://www.analogic.co.uk/shop/amiga/a4000/shop-amiga-a4000-chips-and-roms-html.html)
Good luck.
Weed.
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I have a spare (heavily corroded) rev B MB with a Super Buster 390539-11 on (same as on the MB I have problems with), I will try that one and see if I get a different result from DiagRom 1.3.
Thanks