Boot Diagnostics (Amiga 1200)
Below are some steps you can use to try and diagnose no boot or issues during boot.
Start off removing all expansion ports, hard drives, floppy and so on, to use just the bare board.
Apply a known working good power supply and check all power rails are stable.
We will test boot with two main states.
- With DiagROM installed in the Kickstart
- With No Kickstart Installed + PiStorm in expansion Slot fully configured to boot
The goal here is to get to the DiagROM boot screen at least, to allow further diagnostics.
To get the DiagROM to boot we can remove the following as they are not needed to get to a boot screen:
- All RAM (U16/17/18/19)
To get the PiStorm to boot we can remove all of the chips above from the DiagROM boot, plus:
- Kickstart ROMs (U6A / U6B)
The PiStorm emulates the following components on the board and effectively bypasses them:
- CPU (U1) although this is still needed to initially run the PiStorm
It still requires the following to be fully functional:
- RAM (U16/17/18/19)
- ADV/VP101 (U30) for video output
- CIAs (U3/U8) to interface with externals
When you have the PiStorm installed, you will get the normal DiagROM activity for a few seconds, then the PiStorm will restart the Amiga and run its own action. This means when reading the With PiStorm statements below, the With DiagROM statements would also run first for a few seconds.
For example, No RAM would be flashing red/green screen for a few seconds (as the DiagROM is running) and then Solid green once PiStorm kicks in.
If you can boot into PiStorm DiagROM without real ROMs installed on the motherboard, but installing ROMs on the real motherboard then stops the PiStorm booting, this is typically the GAL16V8 (XU1).
With a bad XU1 you can remove the U6A/B ROMs and use a PiStorm to still boot. You must have U6A/B empty though otherwise it won't boot, as you will get bus contention between the ROM and other ICs.
As there are many general components that are responsible for boot, such as resistors, capacitors, good traces, crystals, clocks, AV connectors, power rails and many things, it is best to focus on the most common and critical chips first when diagnosing.
Below are the components that are absolutely needed to get boot:
- CPU (U1) even if using PiStorm, as CPU needs to read from expansion slot
- ADV/VP101 (U30) needed to see anything on screen
- GAL16V8 (UX1) otherwise flickering or no sync
What I typically do to help diagnose issues with not even getting to DiagROM boot screen are the following.
Initially, clean the board fully, change the Kickstart ROM sockets for new turned pin headers to make sure they have good contact as that is a common issue. Use a known working power supply and AV cable.
Remove PiStorm and ROMs from U6A/B so there is nothing in the slots.
Turn on. If I see 50/60Hz on screen regardless of what's on the screen it that helps to prove in general the power supply, ADV/VP101, AV cable, receiver TV/monitor are all generally good.
If this fails and you have no sync on screen at all, then I would check power rails, clocks, crystals, shorts (anything getting hot or rails loading down) and make sure all the board is free from fluff, rot or trace damage firstly.
After this (getting a signal on screen), I would keep the ROM slots empty and add the PiStorm to the expansion slot, loaded with the DiagROM as the kick.rom file.
If this boots, then run the following tests to confirm functionality of the following chips
- Memory Tests - Dedicated Chip Mem (checks U16/17/18/19)
- CIA Tests - Test CIAs (checks U3/U8)
This way you know all those chips are good, and the CPU (As it has to work to run the Expansion port, although it doesn't need to fully work to run the entire system so it could be partially working).
We know also the entire video output circuit then works too in order for it to boot that far, so the ADV/VP101 is good too.
If removing the PiStorm and using real DiagROM in the Kickstart does not work, the likely suspects are the components or traces to them that the PiStorm is bypassing:
- ROM sockets (U6A/B) or ROMs themselves, traces to CPU and other chips
- CPU (U1) traces more likely than actual bad CPU, reflow CPU
- Gayle, Alice, Budgie, Lisa ? (Unconfirmed if these are bypassed by PiStorm)
With the system in the state mentioned above, resort to the table below for hints:
With DiagROM | With PiStorm | Possible Cause |
|---|---|---|
Flashing red/green | Solid green | No RAM / Faulty RAM (U16/17/18/19) |
All Black Screen (no border) | All Black Screen (no border) | Bad CPU / Kickstart |
Freezes after Doing ROM Checksumtest green lines | Boots fine | ??? |
Black screen then no screen | Without ROMs installed, boots, otherwise colored screens | GAL16V8 (XU1) |
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