Description of reset 'sequence'

[Chain]

Hi A11,
where i can get deep description - something like "How things inside amiga works after keystroke Ctrl-A-A"?
I still have problems with one of my A1200. Some signals are sended after reset, but miggy cant boot, no floppy seeking, only black screen.
There must be big difference between 'cold' start and restart.
Any ideas? Help of any kind desparately wanted. :-(

[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.

[Chain]

Absolutely NO PATCHES, only bootscreen or early-startup menu.
I want to know something like this example:

0. start, power up
1. paula send xxx into xxx, this make  xxx
2. all registers set to 00000 blah blah
....
blah
....

15. Insert floppy screen appears.

[Thomas]

There is a detailed description in the RKRM:Libraries in the section about expansion.library I think. And there are commented ROM disassemblies around. At least I had one of Kickstart 1.3.

From memory I'd describe it like this:

First thing is to set the power LED bit in the CIA. Then it sets the screen background color to dark grey or something. Then it checks the ROM checksum. If it is incorrect -> make the screen red and guru. If it is ok -> check if there is a valid pointer to exec.library base in address 4. If it is (warm reboot) -> call the resident modules. If it is not (cold reboot) -> find the amount of chip ram by a ram test (if it is less than 256KB -> make the screen green and guru), find the amount of fast ram by I don't know what (IMHO autoconfig is not yet active), create the exec.library base, initialise expansion.library and do the autoconfig stuff to include all the expansions.

Now we are back from both cold and warm reboot and have a list of bootable devices. Check for a bootblock from highest to lowest priority, load and execute the boot block. The boot block initialises dos.library (at least for floppy disks, HDDs work different).

There is not a big difference between cold and warm reboot. It just reuses the exec.library if it is still there. And exec.library base may contain a list of resident memory areas which are allocated automatically and a list of resident modules which are called automatically.

Bye,
Thomas

[SHADES]

@ Doobrey

Nice, can you elaborate a little further, which address lines get checked, do they pull low, bus restes CPU check what initalise pins etc?? Seting up of IRQs??

All that kind of detail is very welcomed for someone like me doing repairs. I have had so much trouble finding this kind of detail, I have schematics and that helps, but the initalisation sequence stuff, Please, if you have time, go though step by step and submit it!!

[peetee]

here are what they mean hope this helps

The first colors you will see are shades of gray .. dark gray, middle gray, light gray, and then white. The RGB color values are 0x444, 0x888, 0xAAA, and 0xCCC, in that order. Colors shown before the four gray shades are artifacts from the original values in the custom-chip registers and do not indicate a failure.
The failure mode screen colors:
turquoise (0x0CC) (A1000 only) RAM failure in the Kickstart WCS
green (0x0F0) error in the lowest 256 bytes of Chip RAM. Possible causes, defective CIA-A IC or defective Agnus IC.
yellow (0xFE5) an unexpected processor exception before the appropriate system failure message was prepared. This could mean defective hardware or an attempt to access a RAM address where no RAM exists.
red (0xF00) invalid KickStart ROM checksum.
magenta (0xF0F) single-task or cold-start initialization failed.

Here is another interpretation of the Amiga boot colors: Above problems combinedVideo scrambled
RED   Kickstart ROM error   Two ICs in A1200, A3000, A4000
BLUE   Custom chip problem   Denise Paula Agnus
GREEN   RAM error   
YELLOW   
LIGHT GREEN   CIA (U7/U300) problem   
BLACK   CIA (U7/U300) problem   If not booting
DARK GRAY   Hardware tested OK   
LIGHT GRAY   Software tested OK   
LIGHT GRAY   CIA (U8/U301) problem   Stops at gray, CIA defective
BLACK/STRIPES   ROM or CIA   
No video   R406 or R215 open   R406=1 ohm R215=4.7 ohm
Agnus or Denise defective   

If the Amiga caps lock key LED blinks repeatedly at boot up, another series of error messages must be consulted:
one blink . keyboard ROM checksum error
two blinks .. RAM failure
three blinks .. watchdog timer failure
and not part of the official specification, but observed by the keeper of this page:
on the A500, multiple repeated blinks indicate low voltage on the 5-volt line from the Amiga 500 power supply

[Chain]

WOW, thanks!
So think i have some problem with CIA:
BLACK CIA (U7/U300) problem If not booting

Where i can get those ROM kernels descriptions for A1200?
Im making some little repairments too, those damn colors arent in A1200 service manuals!

[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.

[spirantho]

Hmm... if I may hijack this thread a moment...

I have problem with a 600. In fact, I just bought another motherboard off eBay and it has exactly the same problem!

When the machines starts up, the caps lock light comes on. And stays on. It'll stay like this for up to an hour or so. After that, it'll go off, the hard disk will power up and the machine boots up perfectly normally as if nothing was ever wrong. If I then reset, the same thing will happen except it'll only take a few minutes to boot up (still much longer than it should). Switching it off, waiting a few seconds, then back on again, results in a delay of a few minutes also.
I've tried both motherboards with nothing connected at all, or fully laden with disks etc, same thing every time. 2 different PSUs, too.

Looking at what you're saying, though, it looks like the PWR_BAD line may be being held low - maybe a dodgy cap or coil or something...

Are there schematics for an A600 so I can find out which pins I should be looking at with my oscilloscope to find out what the heck's happening?

Any help or technical info would be greatly appreciated!

Thanks!

[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  :-(

[spirantho]

Nope, three different PSUs in total.

I thought that maybe it just wasn't booting because I hadn't plugged anything in to it (even the keyboard) but my 1200 boots fine with nothing plugged in.

I shall take a look at the +5V line and see if it's got a bad ripple or something.

Thanks for the link to the schematics, though - should be very handy!

Edit: Can't find anything on any PWR_BAD line though - which chip is it on? Can't see it on the schematics either...

[SHADES]

@Doobrey
Thanks for this. I need to know at what point these things are initalized. I.E. What part of the initalization sequence does the IRQs get initalized and by what pin of what chip and how, and what correct voltages should be present etc. That's the thing, I need detail. I have Hanies archive and I have had to write down some for myself through trial and error but as you are aware, there are very few AMIGAS being used now and I'm not asked to repair that many 4000s any more. It's been years since I have had a working 4000. If I had one, I could compare the two and repairs would be a hell of a lot quicker and easier. Just got to track it all down somehow. Rob from AmigaTechnologies Aus used to have it all, but he dissapeared and took all this info with him. Such a shame!! could be so useful!!! just post notes on to the net or aminet, anything!!

[Chain]

Just another little thing:
When reset fails, Alice and CPU is very hot after few seconds.
I think there must be some very intensive cycling operation, damn

[Chain]

A1200 tower reset from TP2 pins does not work too, guys

[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....