A600 8Mb fast expansion

[rkauer]

 Where can I find this project?

[rkauer]

 Without another processor (<>68000) you cannot use more than 8Mb inside an A600 (68000 use a 24bit address space = 8Mb).

[rkauer]

 I could be wrong (sometimes I am), but the SIMM itself is merely a little board to held the memory chips.

 So all you have to do is modify a little your board to put a SIMM socket in it. That way the user can choose any SIMM he/she have.

 Or the Altera chip must be "notified" of the size of the bank?

[rkauer]

 BTW: where can I find the schematics to place a 1Mb SIMM in the trapdoor of mine A600?

[rkauer]

 A really bad solution for this issue is put a switch in the upper address line of the memory/SIMM to trick the board as only 4Mb is installed, instead of the full 8Mb.

 The better of two worlds: 4Mb and free PCMCIA port or 8Mb in your A600!

 My only concern is the Altera chip: it needs to "know" previously the size of the memory?

[rkauer]

 Doing this you'll have more complexity in the board layout.

 I simply prefer the SIMM header to solder any bank of memory I choose. Even if the SIMM fails, it's easy to swap for other bank (although it have to unsolder the bad first).

[rkauer]

 But then you need to change the Altera chip for a bigger one or even use some kind of "mini" CPU to control the memory chunks.

[rkauer]

da9000 wrote:
@rkaur:

I assume your response was for me? If so, I'm only asking so I can understand, not so much to have lordv do this. Version 1 is key, the rest is fantasy for now :-)

 Yes, it was. Add complexity to a simple, but elegant design is not good for a starting hardware. Like Minimig, baby steps, baby steps...

[rkauer]

lordv wrote:
--zip--
SIMM sockets are indeed very hard to find except for desoldering them from old PCs (and more, they should be laying and not standing as in majority of PCs). I don't think this way is acceptable.

 So why bother with connectors? Simply leave the copper traces to the final user solder a SIMM right in the place! SIMM banks are common as mud, but the socket isn't.

 With this you have a low profile board.

 For the contact issue in the processor side, exists a simple fix: put two plastic stands on the far side (ports side) and a screw in the frontmost side. Jens did this in the aka630 accelerator. Much better than put some kind of glue to keep the board in place.

[rkauer]

 Just up the thread!

[rkauer]

1NOM155 wrote:
why a jumper for 0 - memory? and can be possible to use SIMS or ram sockets?

 Jumper for zero: just for compatibility.

 2nd answer: not without a major redesign of the board itself. Maybe in version 1.3.

[rkauer]

alexh wrote:
Why does anyone care about sockets and SIMMS etc. if the boards come fully populated with 8Mbytes soldered down and a jumper?

 Because not every SIMM have the same chips on it. With using traces to solder your own SIMM (or a socket) you'll be able to put any SIMM you like.

 A board with traces to directly solder memory chips make that board exclusive to just one type of chip memory model.

[rkauer]

 :bump:

[rkauer]

rkauer wrote:
Because not every SIMM have the same chips on it.

alexh wrote:
Did you read what I put? What does that matter if they are sold with the memory already populated?

 I mentioned it because maybe the board could be sent without any chips (bare board).

[rkauer]

:bump: