A2000 chipram upgrade

[krakonos]

Hi@all,
I have an A2000 (rev.4.1) and I would like to upgrade from 512KB chipram to 1MB. I have an Agnus 8375. Can I use it without any adapter (like DKB megachip)? I don't need 2MB chip, just 1MB. Or have I to buy 8372 Agnus?
And can I simply replace the old Agnus with a new one?
Or are there some special instructions?
Thanks much.  

[Xamiche]

I added 512KB RAM to my a500 motherboard, made some jumper changes and enabled 1MB chip RAM all with Agnus 8372A. I'm not sure if that would translate to an Amiga 2000 though.

[krakonos]

Thanks Xamiche for your reply,
still need to know if you can use 8375 instead of 8372

[Damion]

krakonos wrote:
Thanks Xamiche for your reply,
still need to know if you can use 8375 instead of 8372

Yes, it should work fine.

-edit- 8375 will work in place of 8372 for addressing 1 MB chip, but as Xamiche says you'll have to modify the board. (Trying to find those docs ATM...)

[rkauer]

krakonos wrote:
Thanks Xamiche for your reply,
still need to know if you can use 8375 instead of 8372

 They are not pin-compatible.

 Short answer: No.

[Damion]

rkauer wrote:

krakonos wrote:
Thanks Xamiche for your reply,
still need to know if you can use 8375 instead of 8372

 They are not pin-compatible.

 Short answer: No.

Yeah, I missed the part about his board being Rev. 4.1. I know 8375 will work in place of 8372 (for addressing 1 MB), but there seems to be some confusion on whether 8375/8372 is compatible with 8370. (As you say, perhaps not?) Anyhow, I believe he'd have to change J101 and cut a trace (looking at the MegaCHIP docs)... and I'm assuming the system would then see an additional 512k of (autoconfig) expansion RAM as CHIPRAM? :shrug:

 

[countzero]

the rev4 a2000 mobo I have doesn't have any empty ram slots. the ram is also organised as 4 rows of 8 (1x128k) chips so it seems mission impossible my friend.

http://amiga-hardware.com/download_photos/a2000rev43mb.jpg

[Matt_H]

Anyhow, I believe he'd have to change J101 and cut a trace (looking at the MegaCHIP docs)... and I'm assuming the system would then see an additional 512k of (autoconfig) expansion RAM as CHIPRAM?

I believe that's correct. I feel like guides for this change used to be all over the place but I can't find any now...

[Gilloo]

krakonos wrote:
Hi@all,
I have an A2000 (rev.4.1) and I would like to upgrade from 512KB chipram to 1MB.

No Impossible with rev4.1.
You need at least rev4.3 or rev4.4 to manage 1 Mo chip by cutting jumper J101 (unsoldering this track).

[Zac67]

As long as it's square PLCC Agnus, you can very easily upgrade the chip RAM to 1 MB. See this thread for compatibility info of the various 8375 models. Only the very early German A2000(A) Rev 4.0 can't be upgraded.

Once you got the 1 MB Agnus in place, switch J101 to 2-3 and open J500.
J101 remaps the $C00000 'ranger' mem to its original position at $080000 (just behind the first 512KB of chip RAM) and J500 open disables the (now mirrored) RAM at $C00000.

[krakonos]

Thanks guys for all your help,

so I'll try to switch the J101 to 2-3 position
and cut the J500 trace and we will see...

Btw, the old Agnus is 8371 (318071-01)
and the new one is 8375 (390544-01).

[Zac67]

According to BBoAH, 390544-01 is an A500+/A600 PAL Agnus for 2 MB - probably won't work in a 2000.  :-(

[krakonos]

Thx Zac67,
so there is nothing like 2MB 8375 PAL for A2000?
I see only A2000 2MB 8375 NTSC there :-(

[Matt_H]

8375 definitely won't work. You need an 8372(A) - ECS 1MB Agnus.

[Zac67]

Matt_H wrote:
8375 definitely won't work. You need an 8372(A) - ECS 1MB Agnus.

Not true, mate. Some 8375 are compatible with A500/2000s. In 1993 I got a bunch of them as spare parts directly from C=:
318069-16 PAL
318069-17 NTSC