Suspect kick rom dead A600

[Mamejay]

Hey guys,
I have an Amiga 600 revision 1.5 motherboard.  Brought a 4mb board for it.  Went to install it and noticed that my rom switcher board could  not be installed at the same time as it would not fit.
I have a 2.05 rom and a 1.3 rom installed.

Removed the switcher and just installed the 2.05 rom direct.
Now I just get sometimes a blue screen then it shakes and goes black or a green screen, it shakes and goes black.
i installed the 1.3 rom standalone and that works fine.

I got a friend to burn me a 3.1 rom to a 27C400 eprom to see if I could  get it working but that did not work.  He made sure he did the byte swap  on the image before burning.  That did not work either.  Not sure if it was burnt correctly.

I got myself a eprom writer and decided to play around with the suspect 2.05 rom.
I read it and byte swapped it and then started WINUAE with it and it worked fine.
I am getting worried now.  What could it be?  Anyone else seen this problem?  Any suggestions?
What is different about the 1.3 roms compared to the 2.05 roms?

[alexh]

I've already answered this in another forum.

KS1.3 = 256Kbytes
KS2+ = 512Kbytes

If a KS2+ ROM can be read correctly on the EPROM programmer but doesn't work in your A600 it probably means address line 19 is broken between the ROM socket and the CPU.

_OR_

If a particular EPROM has _NEVER_ worked it could mean that the EPROM is too slow.

Does KS2.05 work if you put it back in the kickstart switcher?

[alexh]

OR

The RAM upgrade is made / fitted incorrectly and is interfering with the CPU it sits on.

http://wiki.classicamiga.com/Amiga_boot_error_code_colours

[Mamejay]

I've already answered this in another forum.

KS1.3 = 256Kbytes (18 address lines)
KS2+ = 512Kbytes (19 address lines)

If a KS2+ ROM can be read correctly on the EPROM programmer but doesn't work in your A600 it probably means address line 19 is broken between the ROM socket and the CPU.

_OR_

If a particular EPROM has _NEVER_ worked it could mean that the EPROM is too slow.

Does KS2.05 work if you put it back in the kickstart switcher?

Thanks for that.  I have been trying to determine which trace couple possibly be broken.  So which pin on the CPU would it go to so I can perform some continuity tests on it?

[alexh]

Pin 48



http://www.symbolengine.com/index.php/2007/05/14/amiga-600-schematics-in-pdf-format/

[Mamejay]

Pin 50



http://www.symbolengine.com/index.php/2007/05/14/amiga-600-schematics-in-pdf-format/

OK.  I did some testing and found that pin 50of the CPU connects to pin 1 of the kickstart socket.  The thing is the KS rom is installed starting at pin 2 on the A600.  Should pin 1 and 2 be tied together?

[alexh]

Ah, perhaps I had the wrong pin, i assumed it was byte addressing. Perhaps it is word addressing.

In that case it would be pin 17?

[alexh]

Sorry, but I'll have to leave it to you to work out which pin on the 68000 maps to the upper address bit of a 512Kbyte ROM.

[Mamejay]

The kickstart rom I am using is a genuine rom if that helps.
I have been comparing the rom chip with the CPU diagram you posted.
http://www.amiga-stuff.com/hardware/4mbit-maskrom.html
I cannot determine any broken traces.  Just checked pin 17 and it traces back to D2 on the cpu.
i think I have to spend more time on it tomorrow.

[alexh]

You're not reading the schematic diagrams correctly.

You are confusing function numbering (e.g. A17) with pin numbering (pin 17).

[Mamejay]

I am learning as I go mate.  Yeah I gathered that A17 was for address line 17.  So far I have traced most of the address lines and they all look fine.
I will wait for the know working 3.1 roms to arrive and hope there could just be a problem with my 2.05 roms.
After that I will look into it further.

[alexh]

If it used to work in the kickstart switcher. Take out the RAM and put the switcher back in and see if it still works?

If the ROM is broken then it shouldn't work.

[Mamejay]

That's the first thing I tried.  I really suspect the ROM is stuffed.
I should have my 3.1 roms by next week so I can be put out of my misery.  I have also ordered a bunch of 27C400 eeproms to have a play.
I want to try and make a dual rom image as I have read about.

[alexh]

You need 27C800 for dual kickstart on A600.

One 27C400 chip has a capacity of 512Kbytes which is 100% used with Kickstart 3.1 40.63 which is 512Kbytes.