A4000 Acill - Issues booting with Diagrom

[amigasquirrel]

Hi there,

I’m building an A4000 D using the Acill 1.0 board and having a few issues, testing with diagrom over serial port.

With a A3400 CPU card installed, it detects Chipmem ok but get stuck at this stage:

Code: [Select]

---- Startupflags done
It will sometimes show:

Code: [Select]

---- Startupflags done

Testing if serial loopbackadapter is installed: <> NOT DETECTED
And occasionally fill the screen with repeating garbage characters after this.

With a BFG9060 and 50mhz 68060 installed, no serial output from diagrom, power LED does not flash.

Scope traces with the A3400 CPU Card:

Address
https://drive.google.com/file/d/1o18e7uQAPMfzgIrXc9zU3iPK14wg8qKL/view
https://drive.google.com/file/d/1iwEmi1CTxtlL1LohLnuBYj7dMuu8zNNU/view

Data - this does not look right at all ?
https://drive.google.com/file/d/1rMXfwuInlokitBYgWkAUu1qwJwkGUHlD/view
https://drive.google.com/file/d/1uxz-XCAC1Wjt8l3__8PWp5qqn91aNh0f/view

Scope traces with the BFG:

Address – why am I only getting around 3.5v ?
https://drive.google.com/file/d/1Yzml4t_dvluUD604lfJoE-LN6TciUWWG/view

Data – what is going on here ?
https://drive.google.com/file/d/1J4XWSmgVVbGp4zWJkzcwf-8HfTiJEl3P/view

Can anyone give me an idea what the problem could be?

Thanks,

[amigasquirrel]

Hi there, thanks for the reply.

Just to clarify the CPU board that does work is the standard A3630 board with a 25mhz 68EC030, it's just labelled A3200/A3400 on the PCB which confused me - apologies!
It's this one here: https://amiga.resource.cx/exp/a3630

With no RAM installed I was getting different results powering-on each time from the memory scan. Instead of all "X" I was occasionally getting random "-" which suggested something wrong on the bus.
I have all the PLCC custom chips in sockets, installed with solder paste and hot air. They are good quality 3M sockets and bases have not been cut out.
I got some unusual resistance readings between pins on the sockets, so removed and re-installed them. I did find some tiny solder bridges, and resistance readings between pins are correct. I think some of the solder paste got stuck to the socket when first installed.

The board has been ultrasonically cleaned using professional PCB cleaner / flux remover so there shouldn't be any issues there, cosmetically the board looks excellent.

After fixing the solder bridges and verifying with magnification, I get repeatable memory scan results every time I power on with no RAM, as shown below:

https://drive.google.com/file/d/1LEPhzwvqJf4TVlG1bM6I0CZ7XbgRmXy4/view

With Chipmem installed, here is the full output:

https://drive.google.com/file/d/1km3csTpd9oCiic_KsY1CSDjFWRNQr-TN/view

At this point all bus activity stops.

I've tried various different SIMM's - same results every time.
Buster and Ramsey are not installed.

Motherboard jumpers J100 and J104 are set to INT with the 68030 CPU card, it does not boot if they are configured any other way.
The 68030 board is original (not a reproduction) and sold as working but I don't have a spare machine to test in to verify this.
I was curious to see if the noise with the 68030 on the data bus was normal, I don't have anything to compare it to.

I don't see any noise with the BFG installed just mixed 5v and 3.5v logic levels as shown here:
https://drive.google.com/file/d/1J4XWSmgVVbGp4zWJkzcwf-8HfTiJEl3P/view (fixed access to this link)
Yes, did some research and apparently the CPLD's used on the BFG are 3.3v output but 5v tolerant input, so that confirms why I'm seeing both levels.

I was thinking of removing the PLCC sockets as I've heard they can add extra capacitance and cause noise, but I've seen some people use them without any issues.

The build is using all new parts apart from some of the custom chips.

I'll have a look at the clocks as you suggest, and a probe around at a few other things.
Any other suggestions welcome, I'm new to Amiga hardware projects.

Many thanks,

[amigasquirrel]

I see you're using the new v2 DiagROM.  I'm not familiar with it, though as I recall from previous version DiagROM, the point where it's stopping for you is around the point where it actually starts using the memory.  If the memory isn't working correctly at that point, it will behave as you're describing.  The newer DiagROM suggests it's only doing a quick memory scan in 64k blocks, not a complete (slower) memory test as the v1.21 DiagROM did.

Might be worth using DiagROM v1.21 which will do a complete memory test, so you can be more confident that the memory is all working correctly, as opposed to the faster 64k block test.

I also don't know how DiagROM might behave with a partially populated board.  Unless you know for sure it'll work (I don't), it might be worth populating missing parts.

I tried populating the rest of the board and no difference with the DiagROM.

When using a Kickstart ROM instead, and I get a green screen with continuous reboot loop.
Some people say this is usually a chipmem issue but could be many other things.

I'll give it a go with a earlier version of DiagROM and see what happens.

Many thanks,

[amigasquirrel]

Here are the results with DiagROM v1.3:

https://drive.google.com/file/d/1dmL--t6pT_sraezgbofP7q8tJRchmmV-/view

[amigasquirrel]

That's very helpful, thanks.

I found some bad connections on U212 so the column / row signals weren't getting to the SIMM socket.
The address lines all look good with activity as you describe.

With that fixed, I'm still getting exactly the same errors in DiagROM so not sure if the SIMMs I'm using are compatible.
I have some 4mb and 8mb SIMMS which do work in an A1200 accelerator, I read that on the A4000 SIMMS larger than 2mb can be used for Chipmem with anything over 2mb being ignored.

Screengrabs of Data, Address, RAS and CAS are here:
https://drive.google.com/drive/folders/1zjyvoUuEbn07Llb7Nor7b_-bzXTPaY6F?usp=drive_link

I've ordered some 2mb SIMMS so will give them a go when they arrive.

[amigasquirrel]

Since you've found some bad solder joints at U212, there's a good chance there are more problem solder joints elsewhere, meaning there are potentially other problems that haven't shown up yet.  I'd suggest a complete inspection of all solder joints.  You can use a scriber to check individual joints by pressing the IC lead sideways; if it moves easily then it's not soldered.  Also do a visual inspection to check for possible solder shorts between leads/pads.

That was the exact problem, a dry solder joint on socket for U901 - looked like it was okay but the pin wasn't actually attached. After fixing that, DiagROM boots into the menu. 
The address/data bus scope traces are looking much cleaner with sharper edges and more like what I would expect. The intermittent slow rising pulses to around 2v have gone, i guess they were caused by a bus conflict and hopefully that hadn't damaged anything.

I was still having issues with stability though so removed sockets from all the PLD's and the system is significantly more stable now, it repeatably boots into DiagROM and stays running without any crashes.
This is using a 4mb SIMM for Chipmem which is correctly recognised as 1mb, memory, IRQ and sound tests are all good.

Having an issue with the display though, here's a video of what's happening:
https://drive.google.com/file/d/1C8woa8CZmVo20MxgregjlW7PXLK-wSqe/view
This display sequence is consistent every time.
I've swapped out U460 for a spare and I get exactly the same output so that's fine.

I still have U400, U211, U450, U300, U350 in sockets, do you think it's worth soldering them also?
U700 and U890 are not fitted for now until I get the display working.

I'll send you a message about some 2mb SIMMs as it would be nice to have some proper 2mb modules.

[amigasquirrel]

What does the display look like with standard OS3.1/v40.68 ROMs?  The board will need U700 and U890 fitted, after which it should be able to boot to the insert disk screen.  Without U700/U890, I expect you'll get a yellow screen.

With standard Kickstart ROMs and U700 and U890 removed I get a yellow screen. This is the same if U700 and U890 are installed.
If I try DiagROM with U700 and U890 installed, I get the same sequence of screens as shown in the video. No FastRAM is detected either.

I doubt there's any issue with the video DAC.  If there is a problem, it's more likely to be something related to the display generator, U450.  Given what you've seen so far, a problem solder joint somewhere would seem likely.

I've removed U400, U211, U450, U150 from sockets and soldered them directly and I still get the screen as shown in the video with the vertical lines -
there are definitely no issues with the soldering of these.

I now have a 2mb SIMM for ChipRAM which passes the memory tests ok.

[amigasquirrel]

Made some progress with the FastRAM, it is all now being detected correctly and error free over multiple passes.

Looking at U450, the clock outputs, inputs and CCCAS all look correct.
The address and data lines still look unhappy.
I'm mostly seeing normal activity, but periods where there are slow rising edges and transitions around 2v which suggests there is contention of some sort.

I've uploaded some examples of some of the bad periods of activity here:
https://drive.google.com/drive/folders/1GNeH8fGFwvHWA59Sj3_IFeuRn2uBZu7H

The IC's are all supposed to be working, either new old stock or tested used.
U700 is not installed at the moment until this issue is solved.

Thanks again for your help.

[amigasquirrel]

I've compared all the signals on U450 to those on a working A1200, and they are all the same.
Clock inputs and outputs are all identical, and so is _CCCAS.
The data and address bus shows the same activity and "noise" as the A4000. My probing setup is probably less than ideal so that might not be helping.

Think it might be time to swap U450 out and see if anything changes.

What's unusual is when comparing the DiagROM display sequence on startup between the A1200 and A4000, the A4000 shows the same sequence, up until the point when the menu should be displayed. I wonder what DiagROM is doing just before it displays that screen. I'm using the same DiagROM in the A1200 and A4000 so it's not an issue with the ROMs.

[amigasquirrel]

The issue with FastRAM was a bad connection to one of the RAS/CAS lines on U890, after fixing that it all started working. The finish on the legs of some of the NOS IC's isn't very good (presumably due to age) so it appears what looks like a perfect solder joint isn't necessarily making a good connection at high frequency. Had to clean up the legs so they look nice and clean, and re-install that made a big difference.

I decided to swap out U450, and got a display as a test I put the suspect U450 in my A1200 as a test and got exactly the same display so we know that is definitely faulty. Installed U700 (DiagROM works fine without it installed) and managed to get it booting properly into Kickstart and workbench, and was able to run some software.

After playing around with that for a few hours, powered it on and was occasionally getting no display. Went back to DiagROM and when there was a display, started to get weird issues where I couldn't get DiagROM output on the serial port, but the serial tests would pass with characters getting sent and received.

The the system started misbehaving, not wanting to boot at all. Power supply started making a chirping noise (no idea why as I hadn't changed anything) as if it was shutting down and restarting - never a good sign. Checked all the voltages, everything looks correct. Tried another power supply, no difference.

Without changing anything, DiagROM then started to output in the serial port again but started to crash at "Set all DMA enablebits" and the system has got steadily worse since.

I'm now getting no H sync / V sync, no activity on the serial port even with all RAM removed.
Occasionally I'll get a burst of activity on the CPU bus, but it's mostly dead and stuck at 5v.
Clock inputs to U450 show little/no activity as if they are being dragged down, so something has died. 

All I can think of doing now is removing U450 and see if I start to get some activity, it felt like it was getting a little warmer than usual.

[amigasquirrel]

I removed the replacement U450 (which was borrowed from my A1200) and the master clock input now looks correct, so the IC is definitely faulty and was pulling the clock down. Why that's happened I have no idea, maybe it didn't like the stress of the hot air removal.

As test I installed the original U450 (that was displaying the vertical lines) and the system is working again as before, so at least that's something. Was getting worried that something catastrophic has happened.

Still wasn't getting a serial output and discovered that the +12v on U304 was nearer 5v. Measured D175 which supplies +12v_USER and it was 12v on one side, and 5v on the other. Reflowed the solder joint (which looked perfect) and then magically got the correct +12v on the output, and now serial is working again.

So I'll have to get a new U450, and continue on from there. At least I know the system has been fully working, so it should again.

My suggestion would be to get the board more complete (i.e. U700 fitted) and try to get it running with the standard OS3.1/v40.68 ROMs.  If you get nothing but yellow screen exception errors, I can send you a specially modified ROM that sends out debugging detail when it boots to better understand where the software is having a problem.  I can't share that publicly since it contains parts of the original Commodore code.

That would be much appreciated, when the system was fully working I was occasionally getting yellow screens until I removed the RTC. There is no crystal fitted at the moment because I don't want to put it through the ultrasonic cleaner.

You are absolutely right about sockets, when it was running the full OS I found that applying gentle pressure to the board near sockets would make the system crash/glitch, so all the PLCC's are soldered now. I don't think sockets are any use with these old IC's and less than perfect finish on the legs. I also know next time to apply new solder to the legs and remove with solder wick to refresh the coating before soldering to the PCB.