A2000 ROM jumpers on A3000 MoBo

[AmiDude]

I've got this A3000 Rev. 6.1 MoBo. Next to the
ROM sockets are 2 jumpers; J180 & J181.
According to the B.B.O.A.H they are A2000 ROM Compatibility Jumpers:

Big Book of Amiga Hardware

Can I put a standard A2000 ROM on one of the ROM sockets,
if I change the jumper settings?
  :-?

[Jeff]

I have never tried it.  However even if the 3000 would boot, the A500/A2000 Roms would not support the 3000's onboard SCSI controller. You might also loose the 32 bit fast ram. There was a discussion about this somewhere years ago.

Jeff

[AmiDude]

OK, thanks. I don't gonna mess around with it then...
 :-D

[da9000]

I have to resurrect this thread, because I fried accidentaly my dead A3000's ROMs and I'm trying to revive it...

So, has anyone ever been able to use a 256KB ROM (from A500/A2000) in an A3000 with the jumpers J180 & J181 set properly?

Thanks

Jeff wrote:
I have never tried it.  However even if the 3000 would boot, the A500/A2000 Roms would not support the 3000's onboard SCSI controller. You might also loose the 32 bit fast ram. There was a discussion about this somewhere years ago.

I realize the issues about booting from SCSI, but at this point it's ok for me since I'm only trying to see if my A3000 will work - don't care about booting at this point.

BTW, Jeff, where was this discussion? I've been searching around but not finding much :-(

[Zac67]

Well, the service manual says:

J180,J181 ROM Compatibility Jumpers
A2000/500 ROMs: 1-2, 1-2
A3000 ROMs: 2-3, 2-3

A look at the schematics reveals a bit more:
The 2-3 setting ("2M") connects A0 to A17 for both U180&181 (pin 9 to pin 1). The 1-2 setting ("4M") connects A0 of U180 to 5V and A0 of U181 to GND.

The way this might be supposed to work: you need two identical ROMs in both U180 and U181! U180 is the low word and U181 is the high word ROM and that way every other word is skipped - pretty brilliant trick I'd say.

SCSI and 32 bit fast RAM won't work of course - A3000 magic isn't present in A500/2k ROMs (maybe 32 bit RAM can be AddMem'ed, but I doubt this because Ramsey isn't initialized properly).

[da9000]

Interesting! I assumed that only 1 ROM is needed. Wrong! Thanks for looking at the schematics for this Zac. I didn't think to look there or where the traces lead.

Hummm.. now to find 2 A500/2000 2.04 Kickstarts. If I do, I'll definitely try it, because I have no other recourse. Of course, like you said, no SCSI or Fast RAM, but I don't care right now since all I'm trying to do is see if I can get my dead A3000 to relive. If it does, then I'll get proper ROMs for it.

I'll update the thread if I have new results.

[TjLaZer]

Why not just buy a set of proper ROMs and see if it works?  Seems a bit excessive just to save a few bucks!  At this point you need two 2.0x ROMs for the A500/2000, or 1 set for the A3000(T).  Unless you have two 500/2000 ROMs you are going to have to buy two ROMs.  There is a set of 2.04 for the 3000 on ebay for under $7.

[amiga92570]

I could send you some 1.4 roms and kick disk just to see if it works.

[da9000]

I appreciate the advice TjLaZer, but my situation is like this:

The board is dead as of this moment. Paying $40 for the 3.1 ROMs you offered me will be around $45-50 (with shipping). What if the board is still dead afterwards? What if the new ROMs burn themselves? I'd rather not. As for the $7, thanks for pointing it out. I checked them out, but unfortunately they're from a "blacklisted" seller: centsisoft. I cannot allow myself to buy from my blacklist: centsisoft, Doomy, boogiegail, eslapion and a couple more I forget right now.