A500 aca 500+ and 1233n. 2mb chip mem

[rjd324]

I am looking to get 2mb chip. I am not sure if it is possible since indi ace2 is not available and since the BB card is not compatible with the Aca s..?

Is there a way to do it.

BTW I also have Gbapii ++ rtg card.

[rjd324]

I also have the ECS denise and ECS 1MB Agnus. I have free RAM slots on the motherboard. Revision 6.

[Jope]

You need a megachip board to get 2MB of chip. Perhaps there are still some on amibay.

[CubeTheory]

Originally Posted by rjd324

I am looking to get 2mb chip. I am not sure if it is possible since indi ace2 is not available and since the BB card is not compatible with the Aca s..?

Is there a way to do it.

BTW I also have Gbapii ++ rtg card.

BB card? do you mean the BooBip card?

https://www.ebay.co.uk/itm/2MB-RAM-u...sAAOSwDZ1bLAKM

That's good to know. I have an ACA500+ and have been thinking about this.

[cmorley]

No, you need a MegAChip with a 8375 2MB Agnus chip on.

Don't use Gary adapter RAM with an ACA500+ it isn't fully compatible (as listed on the iComp website).

[Jope]

Yeh, the ACA provides you with all the ranger fast you need. No reason to continue using a gary hack trapdoor card.

[rjd324]

Hey. So what is stopping me from soldering another 512k onto the rev 6a, replacing the Gary to the 2MB version and installing a 1MB expansion card? I am guessing that I am missing something obvious that prevents that in resulting in 2MB chip..

[hooverphonique]

Gary is the same, you need a different agnus, but it is not pin compatible with the rev 6 board, that's why you need a MegiChip or similar.

[rjd324]

Sorry. Agnus chip I meant.
So the fact that it is not pin compatible is the reason. That makes sense. So far I have a donor 600 board and I have stolen the ECS denise from it and use the plcc dip converter. Works fine. I will also steal the agnus from it.

Just for the sake of asking general questions:
Say if there was a hardware board that did nothing but make the 2mb agnus compatible with the a500.

Let's say I had this hardware and used it. If I soldered on 512KB additional mem to the board and used a 512KB expansion board, would I get 1.5MB chip mem?

Those mega chips come with memory modules already installed. So I am guessing that the mem in the board is redundant and the mem on the expansion card is redundant. Unless that memory is used for fast/slow.

I don't know how agnus works... Is its first task to seek out any memory it finds and assign it I to the chip ram address space until it is full?

[hooverphonique]

Originally Posted by rjd324

Say if there was a hardware board that did nothing but make the 2mb agnus compatible with the a500.

The 2MB Agnus has an additional DRAM address signal, so you would need to wire that separately to address more than 1MB chipram.

Originally Posted by rjd324

Let's say I had this hardware and used it. If I soldered on 512KB additional mem to the board and used a 512KB expansion board, would I get 1.5MB chip mem?

The short answer is no - if you want to know the details, you need to look at the schematics.

Originally Posted by rjd324

Those mega chips come with memory modules already installed.

Most likely due to the missing address signal on the A500 board I mentioned above.

Originally Posted by rjd324

I don't know how agnus works... Is its first task to seek out any memory it finds and assign it I to the chip ram address space until it is full?

Agnus doesn't "find" memory, it's all done by the Kickstart code. At which address it is detected depends on Gary and the motherboard jumpers (which also selects if the Kickstart considers it to be chip or slow ram).