2mb Agnus... ECS Amigas, chip hacks... what tha?!

Now I am confused.

I always thought that ECS Amigas, with the exception of the A3000, only had a 1mb Agnus, with ECS Denise....

Now Im getting conflicting information. From one source I am being told that a 2mb Agnus will NOT work in an A2000 or A500 unless either installed in a 2mb chip board, such as the Megachip or Chip X etc, OR if it is one of the later revision boards with 8 ram chips (instead of 16) on the MB, then a 2mb agnus can be installed DIRECTLY into the agnus socket as long as a hack that replaces the mb ram (with double capacity chips) and a few other alterations are made.

But WITHOUT either the board or the hack, the 2mb agnus will not function at all, not even as a 1mb agnus returning amb of chip on boot up.

But then, another learned fellow tells me that thats "bollocks!" and rev 6.3+ a2ks and later revision a500s actually came with a 2mb agnus installed which only reports 1mb chip until the above mentioned hack is carried out.

Can someone shed some light on this? I have a revision 6.4 A2k and a 2mb agnus... can the agnus be installed directly to the mb? If so, without the hack will the machine boot (with only 1mb chip of course)? Will the (reasonably simple) hack work?

Put it on simpler words: any Amiga equipped with a socketed & square Agnus can use a MiniMegiChip/MegaChip if it doesn't have a 8375 Agnus already.

The A500 that can be upgraded to 2Mb chip RAM DIRECTLY, just adding more memory chips, are only the A500 rev8A/8A1.

The A2000 can't have more than 1Mb DIRECTLY (just soldering more memory chips), doesn't matter the board revision. Installing a MiniMegiChip/MegaChip is the only way.

Well, there are the mentioned hacks that usually include adjusting the Agnus socket to the pinout of the (to be used) 2MB-Agnus, and adding/changing RAM-chips, like this here for example.

In this case though, the board is a rev. 6.4 - and those already came with an 8375 Agnus (a 1MB-version).

Now, if all versions of the 8375 Agnus had the same pinout (do they?), a 2MB 8375 should theoretically work "straight out of the box" in this board too, but unless the onboard RAM was also "adjusted", there wouldn't be any benefit to this - it would still only have the stock 1MB to work with.

There are a multitude of different Agnus revisions, so approximately everything you've said above is true.

The 1MB-max 'Half-ECS' Agnus is part 8372A and features in r6 A500s and r6.0 -- r6.2 A2000s.

The 8372B is a full-ECS 2MB part that is found in A3000s. I believe it's a drop-in replacement for the 8372A. It may be what's on the r6.3+ A2000s. I'd have to check with someone who has such a model. (Alas, mine's only a r6.2)

The A500+ came with an 8375 Agnus, which helpfully is wired completely differently to the 8372 parts. Stupid! But that was C= for you. I've no idea what the A600 has in it. I've heard rumours that it's pin-compatible with the 8372 range, but nothing conclusive.

Does that help explain things?

Well, what about this - http://www.mylinuxisp.com/~jdbaker/o...shack_v1.4.txt

?

Quote:

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Originally Posted by abraXXious

Well, what about this - http://www.mylinuxisp.com/~jdbaker/o...shack_v1.4.txt

?

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So, dropping a fatter Agnus into an A2000 is fairly simple, the issue is actually giving it that second MB of Chip. There's no designed way to do that on an A2000, so you have to solder on some more memory chips. That's what this hack is about.

Well, that was kinda' my point - so with this reasonably simple hack, you can have 2mb chip on an a2k without a dodgy chip ram board that crashes your system every time a mouse farts within a 5 mile radius?

Okiez, well this rather simple hack requires a rev 6.3+ A2k - check, my system is a 6.4...

It then requires an Agnus chip, but it is asking for either an 8372B or 8375B... which is rather odd becuase one source says the 8372B is a 32 bit 2mb Agnus for the A3k!

Anywho, part number 318069-03 is an ntsc Agnus. I of course have a 318069-10 agnus which is the pal counterpart.

From what I have read they are both pin compatible...

... but since the hack is being done to an NTSC Amiga with an NTSC Agnus.... will it work being done to a Pal Amiga with a Pal agnus?

Quote:

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Originally Posted by abraXXious

Okiez, well this rather simple hack requires a rev 6.3+ A2k - check, my system is a 6.4...

It then requires an Agnus chip, but it is asking for either an 8372B or 8375B... which is rather odd becuase one source says the 8372B is a 32 bit 2mb Agnus for the A3k!

Anywho, part number 318069-03 is an ntsc Agnus. I of course have a 318069-10 agnus which is the pal counterpart.

From what I have read they are both pin compatible...

... but since the hack is being done to an NTSC Amiga with an NTSC Agnus.... will it work being done to a Pal Amiga with a Pal agnus?

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What's the Agnus part you've got in your r6.4 at the moment?

Quote:

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Originally Posted by abraXXious

Well, that was kinda' my point - so with this reasonably simple hack, you can have 2mb chip on an a2k without a dodgy chip ram board that crashes your system every time a mouse farts within a 5 mile radius?

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Technically, all the MiniMegi or other ChipRAM expansion board is doing is exactly the same as that hack, but the second MB of ChipRAM is on the expansion board, rather than the motherboard.