What A2000 MoBo can have 1MB chip RAM ?

[TjLaZer]

I might have a related problem.  I have a early 2000B machine Rev 4.4.  When I got it, it had Kickstart 1.2 in it and already had 1MB Chip enabled.  Problem is when I try to do PAL screen goes black and video is jumpy.  Switch back to NTSC and it works ok.  So PAL does not work.  What could cause this?  It has a 8372 Agnus.

[murple]

Zac67 wrote:
Yes. Since the A2000 - or A2000A - officially: Rev 4.0 - was built based on the A1000 OCS, there's no way to expand it to 1 or even 2 MB chip - other than swapping the board with a later rev.

Well, there is this:

http://amigahardware.mariomisic.de/cgi-bin/showhardware_en.cgi?HARDID=967

That is what I have, it was sold to me by someone who didn't know it was only of use in the bogus 2000s (A2000 rev A). The page there says "This card may not be compatible with Model B & C A2000s" and I have seen info (from Haynie I think) that confirms it can NOT be used in a real 2000.

If anyone has an A2000A and wants the RAM expansion, I've got one. Its of no use to me.

[breech]

This is taken from one of the miscellaneous docs I've been reading, not sure where it's from or who originally wrote it:


Find Jumper J101 located on the lower right side of the power connector CN400, and consists of 3 posts - 2 of the posts are shorted together using a shorting block. Remove the shorting block and move it to the left, towards the power connector. For further info, see Page 13 of the A2000 system schematics - this jumper will enable address line 19 from the 68000 which controls the 1 meg address range.

Locate and cut Jumper pad J500 (to the lower left of the 8520 at U301). This is a 2-pad jumper with a trace connecting the two pads. See Page 9 of the A2000 system schematics - cutting this trace keeps the _EXRAM signal from being tied to ground.

To enable PAL rather than NTSC - locate and cut J102, NOT J201 as suggested in some docs. This is the equivalent of bending pin 41 of Agnes in the A500 mod.

Oooold thread bump because this worked for my A2000 rev 4 and now I can use WHDload :thumbup:

[Zac67]

Well, there is this:

http://amigahardware.mariomisic.de/cgi-bin/showhardware_en.cgi?HARDID=967

(old statement, but still)
No, there isn't. The Ranger mem card you pointed out is real $C00000 fast RAM and it's got nothing to do with chip RAM. Sorry.

[save2600]

Taken from TBBOAH:

J101   This jumper determines the high order address bit for Fat Agnus. In it's normal position, the high-order bit is A23; in it's other position, this bit is A19. The current Fat Agnus chip requires the A23 signal for proper management of the memory at $C00000. Future Fat Agnus chips may do things differently; this keeps the current board compatible with simple enhancements.

J500   This jumper is used to enable the 512k of RAM at $C00000 and the real-time clock. It is normally closed; opening it will disable both this extra RAM and the real-time clock.

Whoops, looks like Lokki posted similar info. This thread is like an adventure through the Bermuda Triangle! lol

[Zac67]

Opening J500 will NOT disable the clock.

Even the SM states this (probably the source anyway), but deactivating _EXRAM will just remove the RAM at $C00000 and has nothing whatsoever to do with the RTC.

[rkauer]

I might have a related problem.  I have a early 2000B machine Rev 4.4.  When I got it, it had Kickstart 1.2 in it and already had 1MB Chip enabled.  Problem is when I try to do PAL screen goes black and video is jumpy.  Switch back to NTSC and it works ok.  So PAL does not work.  What could cause this?  It has a 8372 Agnus.

 Machine locked by the 1.2 ROM / Workbench. Upgrade the ROM & WB to 1.3.