Description of reset 'sequence'

[Doobrey]

Sorry if this is a bit vague, it's all off the top of my head. I'll have a dig for more info later.

Cold boot and reset aren't that different really
When resetting from the keyboard, the keyboard controller holds the reset line low for a short time.
 There can delay this for upto 10secs if needed(eg when using a reset handler), but it can't cancel/stop a reboot.

When cold booting, the reset line is held low until the +5v supply has reached a set level. (Although if the 5v line goes below this point at anytime while the machine is up and running, it will hold /PWR_BAD and /RESET low until it stabilises again)

But on a reset, there can be things still resident in memory (patches/hacks/3.5 or 3.9 romupdates/virus) which can run before Workbench comes up.

So it might be worth checking what patches you've got installed in your user-startup or WBSStartup and run a virus scan to see if the problem goes away before digging out a multimeter.

Edit.
 Have a look at http://main.aminet.net/package.php?package=hard/hack/A1k2TReset.lha, for putting an external reset switch on the a1200, it should work every time,and is a lot easier than diagnosing a problem with the kb controller reset.

[Doobrey]

SHADES wrote:
Please, if you have time, go though step by step and submit it!!

 To be honest I'm not the best person to ask, I've only learnt some bits and pieces of it all.
 Thomas gave the best advice earlier on, download the commented exec disassembly (Aminet link) Although it only deals with the 1.2 ROM, there isn't much difference from the newer roms in the startup part.
 Also get the Hardware Reference Manual (programmersheaven.com)
And there's also some good stuff in the Dave Haynie Archives, the ZorroII specs are very good at explaining the autoconfig part of the bootup.

And as for interrupts, they're all hardwired on the Amiga.
You can see on the schematics what priority different things have (INT2/3/6 shared between several parts)
eg the CIA that does the serial port etc has INT6, the other has INT2. (Both 2 and 6 are also available to any Zorro cards), Agnus can generate an INT3. All interrupts are fed to Paula, which then sets the IPL lines to the CPU.

[Doobrey]

@Spirantho,
 A600 schematics(and others) at Ian Stedman's site http://www.ianstedman.co.uk/Amiga/schematics/schematics.html

 Did you try both motherboards with the same PSU ? Tried measuring the +5v while the A600 is trying to boot..maybe the power bad signal is low for a good reason  :-(

[Doobrey]

Eeek, that doesn't sound good. Unfortuately, all the schematics I've got are on a shared drive on my PC...and Windows is having a hissy fit ({bleep]ing stupid new nvidia drivers, WHQL my backside!  :pissed:)

When you say Alice and the 020 are hot, how hot do you mean?
On my 1200, I noticed Alice and Budgie were 'quite warm', but I could easily hold my finger on them, unlike the RAM on the Geforce card in my PC.

As for the TP2 reset failing, do you mean nothing happens at all, or just the same results as your keyboard reset(ie reset, but not coming back up)?
Gah.. if only Windows hadn't chosen today of all days to have PMT....