Amiga 2000 Green Screen

[Frankencelery]

I've got an Amiga 2000 rev 6.x motherboard that gives an instant green screen on power on.  There WAS slight battery leakage, but the damage, if any, appears to be superficial.  

I know that green screen means chip ram, but I've had no luck so far.  I've installed sockets and replaced all the RAM.  Replaced Agnus AND the socket (gotta love desoldering an 84-pin PLCC socket) and also the CPU socket, because that's the one that always gets the battery damage.  No luck so far.  

Couple other items I forgot to mention.  I am working with the bare board on my bench, so no peripherals are attached.  Also, I don't know if this is important, but the green is instant as soon as power is applied.  There are no levels of gray first.

Any other ideas to try?  I'm open to suggestions!

[Pat the Cat]

Suggest you do a search here for "green screen".

You would not get it if CPU was damaged - at least ROM code to do the tests is being run.

However, the tests are pretty quick and slapdash. A bus error preventing chip RAM from being read may also cause a green screen.

Sometimes is a faulty RAM chip, sometimes faulty Gary or (on an A2000) Buster or Ramsey or even just a short on the slots - old bit of solder, that kind of thing. I've found usually is a short or a corroded socket pin, not a real problem with a chip as such.

Also try swapping the 8520s, if one is bad and causing bus error, might resolve the boot and show the fault to be in an 8520 rather than a RAM chip.

If you do end up swapping out DRAMs (not applicable this case), do fit sockets if not fitted already. Also check Rev 6 mods are all in place and haven't been undone.

EDIT: Pic shows very tidy board. Is cap to left of CPU shorting on pin? Probably not, just optical illusion.

[Frankencelery]

I haven't tried Gary, but I did swap the 8250s as you suggested.  

That cap was not shorting.  I checked.

RAM sockets are installed.  CPU socket was replaced, Agnus socket was replaced, no corroded pins or anything shorted that I've been able to find yet.

I have not checked for Rev 6 mods.  I suppose that's something I can google and verify.

[Acill]

I would recommend you run John Hertells diagrom and see what it tells you. If you dont have an eprom burner to make one I can help you out for the cost of the eprom.

http://www.diagrom.com/index.php/download/

[Frankencelery]

I would recommend you run John Hertells diagrom and see what it tells you. If you dont have an eprom burner to make one I can help you out for the cost of the eprom.

http://www.diagrom.com/index.php/download/

Fascinating!  I had no idea such a thing existed.  This might give me just the edge I was looking for.  Funny you should mention that today.  My company just shut down its legacy business, and among the interesting toys I got to bring home just yesterday was a PROM burner.  My old one was never capable of doing Amiga sized ROMs, maybe this one will.  Now to see if there's any 27C400s around here....

Thanks for the awesome tip.  I'll be sure to come back here and post an update when I have one.

[Frankencelery]

Ok...progress made.  First, the unrelated stuff:

1. Found out my new-to-me eeTools TopMax programmer DOES work, but I had to drag out an old WinXP machine to make it work.  32-bit and Parallel Port only!

2. Found out that I DO indeed have 3 27C400 EPROMS available.  2 of them are bad, but one programmed with the 0.8 DIAGROM successfully!

Now back to the original subject...my ailing Amiga 2000:

3. DIAGROM boots, gives some flashes (green/red), which is consistent with Chip RAM problems.  Connected Null Modem cable.  Wow, this guy has done some awesome work!  The system appears to detect 512K of RAM (should be 1MB), but it fails to scan any of it.  Here's what I get, if anyone can help me decipher this:

Checking memory from $00080400 to $00100000 - Press any key/mousebutton to stop

Checking Address: $00000003  |  Bit error shows max $FF errors due to space

            8|7|6|5|4|3|2|1| 8|7|6|5|4|3|2|1| 8|7|6|5|4|3|2|1| 8|7|6|5|4|3|2|1|
Bit errors: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
Byte errors: 0         0         0         0         Number of errors: 0

Checked memory: 0KB       Usable memory: 0KB        NONUsable memory: 0KB
--------------------------------------------------------------------------------
Bad Block start at $FFFFFFFF and ends at $00000003 with a size of 0KB


Shadowmemory detected. Scan stopped. You can ignore the last error if any!

[Pat the Cat]

IIRC original A2000 shipped with 512K "pseudo fast" and 512K chip... so for some reason thinks it isn't quite a Rev 6 motherboard.

Gary would be my prime suspect, but like I said, typically isn't a bad chip, is a short somewhere. Agnus too but you seem to have covered that base already.

I had no idea about DiagROM either. I guess I am used to diagnosing by swapping chips out...

Thank you too Acii, and to Mr Hertell for doing the work with DiagROM.

Also, check links to select 1MB Chip Ram / 512K+512K split.

Memory map here, looks more like first 256K isn't accessable for some reason... maybe I am reading this totally wrong.

http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node00D3.html

ALso J500 may be set wrong, does not just disable clock, also disables some chip RAM.

http://www.titan.co.nz/amigaak/AA060161.htm

[Acill]

John and I are very good friends and talk nearly every day. If you PM me a list of results and questions I will be happy to pass them on and review them myself. I am in Japan this month on a job, but have internet access thats quite good. The time change just gets in the way some is all. For now I have passed on your last post with the serial output.

[Acill]

If you look at the address  the first 512K of chipmem is not detected..  so I would check the output on serial port to see if there are biterrors.

Since  the kickstart actually had a greenscreen  it is unable to allocate chipmem at first memoryblock (it does it in blocks of 16k if I remember correctly)
while the test rom searches the complete 2MB area for memory.

Post the serial dump here and I will review it.

[Frankencelery]

Hi and thank you for your help!  Is this what you needed?



Amiga DiagROM V0.8 - 22-Oct-16  - By John (Chucky/The Gang) Hertell

- Parallel Code $ff - Start of ROM, CPU Seems somewhat alive
    Checking status of mousebuttons for different startups:

    Set all Interrupt enablebits (INTENA $dff09a) to Disabled: Done
    Set all Interrupt requestbits (INTREQ $dff09c) to Disabled: Done
    Set all DMA enablebits (DMACON $dff096) to Disabled: Done
- Parallel Code $fe - Start of chipmemdetection

Addr $00000400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00000400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00000400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00008400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00008400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00008400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00010400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00010400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00010400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00018400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00018400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00018400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00020400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00020400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00020400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00028400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00028400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00028400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00030400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00030400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00030400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00038400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00038400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00038400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00040400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00040400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00040400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00048400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00048400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00048400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00050400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00050400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00050400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00058400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00058400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00058400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00060400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00060400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00060400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00068400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00068400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00068400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00070400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00070400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00070400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00078400  Write: $F0F0F0F0  Read: $FFFFFFFF  FAILED
Addr $00078400  Write: $0F0F0F0F  Read: $FFFFFFFF  FAILED
Addr $00078400  Write: $00000000  Read: $FFFFFFFF  FAILED
Addr $00100400   OK  Number of 32K blocks found: $10
Startaddr: $00080400  Endaddr: $00100000
  Using $000EE24E as start of workmem

- Parallel Code $fd - Start of motherboard fastmemdetection
- Parallel Code $fc - Memorydetection done
- Parallel Code $fb - Starting to use detected memory
Detecting if we have a working raster: DETECTED
Detected Chipmem: 512KB
Detected Motherboard Fastmem: 15360KB
Basememory address: $000EE24E
- Parallel Code $fa - Detected memory in use, we now have a stack etc
    Set Start of copper (COP1LCH $dff080): Done
    Starting Copper (COPJMP1 $dff088): Done
    Set all DMA enablebits (DMACON $dff096) to Enabled: Done
    Set Beam Conter control register to 32 (PAL) (BEAMCON0 $dff1dc): Done
    Set POTGO to all OUTPUT ($FF00) (POTGO $dff034): Done
- Parallel Code $f9 - Starting up screen, text echoed to serialport
Amiga DiagROM V0.8 - 22-Oct-16  - By John (Chucky/The Gang) Hertell


























                             DiagROM V0.8 - 22-Oct-16

[Frankencelery]

Here also is the dump from the System Info menu option, which may be what you were wanting in the first place!

Information of this machine:

               Dump of all readable Custom Chipset HW Registers:
BLTDDAT ($dff000): $FFFF   DMACONR  ($dff002): $4380   VPOSR   ($dff004): $B000
VHPOSR  ($dff006): $BD9D   DSKDATR  ($dff008): $FFFF   JOY0DAT ($dff00a): $1404
POT0DAT ($dff012): $E0E0   POT1DAT  ($dff014): $E0E0   POTINP  ($dff016): $5500
SERDATR ($dff018): $0B0D   DSKBYTR  ($dff01a): $9000   INTENAR ($dff01c): $0000
INTREQR ($dff01e): $0028   DENISEID ($dff07c): $FFFF   HHPOSR  ($dff1dc): $0064

[EugeneNine]

I would recommend you run John Hertells diagrom and see what it tells you. If you dont have an eprom burner to make one I can help you out for the cost of the eprom.

http://www.diagrom.com/index.php/download/

Interesting.

Looks like a 2000 needs a 27C4000?  http://www.mouser.com/Search/Refine.aspx?Keyword=27C400

Where do you find yours?

[Acill]

Interesting.

Looks like a 2000 needs a 27C4000?  http://www.mouser.com/Search/Refine.aspx?Keyword=27C400

Where do you find yours?

27c400 and I get them from China off ebay. Here is the ones I use and also the same seller.

http://www.ebay.com/itm/10pcs-IC-AM27C400-150-IC-DIP-40-512K-x-8bit-256K-x-16-bit-COMS-EPROM-AM27C400-/191274549477?hash=item2c88da00e5:g:PoYAAMXQKLdRy-xJ


As for the A2000 serial dump I can see the first 512k is totally dead.. so I'd guess power to memory bufferchips or something. Look around for bad traces near them. Check U451 as the fist thing and I expect its bad too, it handles _WE and _RAS1 and RAS0, CASL och CASU. Thats the first thing I would replace. Its an  LSF244 and all memory select signals go through it. Here id data sheet: http://www.mouser.com/ds/2/149/fairchild%20semiconductor_74f244-608438.pdf

[Frankencelery]

Yeah, Mouser is the only place that seems to have those 74F244s.  I ordered some of those, and the 245s.  Gonna be a few days to get those.

I'm glad you mentioned that you were getting good results from an Ebay seller in China.  I bought some Commodore CIAs a couple months back and not only were they counterfeit, but they were all defective.  Made me nervous about buying from China sellers.  I do need some more 27C400s as well.

I didn't want to muddy the waters with too much information, but I thought I might share some more information about this board.  I bought it as a spare, a couple years ago and it has never worked.  I bought it because it was Rev6 and looked to be in good condition with no battery damage.

[Acill]

Hopefully, this is all it is. The fact you can get the diagrom working and are getting a green screen is actully a good thing. It means the KS rom is at least executing its first command.