Help wanted designing A1200 RAM board

[Mounty]

I am in the process of designing a basic trapdoor RAM upgrade for the A1200 (no FPU etc).

If anyone feels they could contribute to this project they would be most welcome.

I would be willing to reimburse serious contributors with the finished product, plus their name immortalised forever on the bottom silk......

[Loedown]

I won't contribute much in the way of circuitry but I will contribute some ideas.

As memory chips change often you're better using a design that's been around for quite some time, using the old SIMM technology with a SIMM socket mount on the edge of the card to accommodate double sided SIMM memory so that people aren't searching for single sided SIMMs or such.

Avoid BGA technology as it's still not mature enough to be really reliable. QFN is ok, can still be reworked easily.

[Mounty]

Hi, thanks for your reply.

Specifically, the help I need is in the area of general schematic, RAS & CAS generation, muxing etc. I can do:

1. PCB layout design right through to Gerber file generation.

2. Fronting the cash for prototyping.

3. Sourcing components.

There must be some designers still around, from back in the day??

[roy bates]

the hardest part on your list will probably be the 150 pin edge connector.

[Mounty]

I have that nailed already, and have designed a PCB pattern for it.

[Loedown]

Originally Posted by Mounty

Hi, thanks for your reply.

Specifically, the help I need is in the area of general schematic, RAS & CAS generation, muxing etc. I can do:

1. PCB layout design right through to Gerber file generation.

2. Fronting the cash for prototyping.

3. Sourcing components.

There must be some designers still around, from back in the day??

There are still people from back in the day and even people like me who came along to the party later. I don't know much about the Amiga timing but I would recommend using something like a microcontroller or similar to interface the memory to the A1200. If it's just a memory interface as you write then some simple logic chips might also suffice.

Some people have better understanding of DRAM than me, I tend to use flash or SRAM.

If you develop the project in parts then people will be able to contribute advice on your progress. My thoughts without delving into the A1200 architecture tell me that;

1. You will have a line that is active high / low to indicate the presence of extra memory. Adding a switch can automatically enable / disable it.

2. If you end up using discrete memory chips ( which I don't recommend because discrete chips are rare enough ) then you will need decoupling capacitors on all the chips. 100nF

3. SIMM memory timing cycles are standardized so you can be fairly sure that most SIMM memory will work with your new card.

4. You will need to know the maximum addressable range for the A1200, might be 4Mb or 16Mb or something else entirely, you may also be able to use a paging system to increase the maximum size beyond that limit depending on critical timing specs.

5. Will the memory clash with a CF plugged into the A1200?


I can help you with info like MUX or signal conditioning, general logic circuitry design and applications. Email is

zero242@internode.on.net

[cpiac64]

good idea

i can add an adapter from 150pin to 68000 for test the a500 ram from kipper?

[Mounty]

Originally Posted by cpiac64

good idea

i can add an adapter from 150pin to 68000 for test the a500 ram from kipper?

Thanks but I'm not sure what you mean by that. Who or what is kipper?

[prowler]

Originally Posted by Mounty

Thanks but I'm not sure what you mean by that. Who or what is kipper?

The designer of this project: A500 4mb-8mb fast ram expansion

[Mounty]

He looks like a clever guy. I need someone of his calibre on board.

[roy bates]

as far as i know you can only address 8 mb's of ram on the native cpu port on the 1200 becauce its 24bit.ec020

you will probably have to incorporate a switch from 4 to 8 mb with a switch on the logic to acommodate the pcmcia port flaws in the rom.

[Mounty]

I'll probably just stick to 4MB to avoid PCMCIA memory clashes etc. That should give enough RAM to run most WHDLoad games.

Like I said I want to keep this as simple as possible. No FPU or RTC support etc. Just something for WHDLoad gamers like myself.

[Nostromo]

Can I pre-order 2 already

Jokes aside, any idea if this will have timing issues like the new ACA accelerators?

[kipper2k]

Originally Posted by Mounty

I'll probably just stick to 4MB to avoid PCMCIA memory clashes etc. That should give enough RAM to run most WHDLoad games.

Like I said I want to keep this as simple as possible. No FPU or RTC support etc. Just something for WHDLoad gamers like myself.

For best WHDload capability you really need the 8mb option. There are quite a few games that work a lot better with the preload option which requires more ram, i'm not sure of the numbers, but i'm sure there are quite a few. I could help with designing the actual board layout, and even the part sourcing but have way too much on my plate at the moment to contribute much more. (I also have my thoughts set on the CD32, but later)

[Turran]

Agree with Kipper here. I have a 4mb Blizzard card in one of my 1200s and I still have to start it with a stripped startup-sequence to be able to play games and still, not everything works as smooth as on the 8mb card.

Of course, on the 8mb card, the PCMCIA slot is useless if you have kick 3.1. Pretty OK on kick 3.0 since PCMCIA works if I have a card in, but only get 4mb memory then.

[8bitbubsy]

Making a switch for 4MB/8MB is super simple, you should add it!

[alenppc]

Someone has made a software patch to reenable PCMCIA with 8 MB and Kick 3.1 in another thread. It seems to be a bit unstable from what I read but it's an option. So 8 MB is always better. A proper patch for this would definitely be needed...

[Turran]

Yeah, I tested that. Not an option...