A1000 or A500 Back plane

[trekiej]

Has anyone considered building a back plane to place a modified Minimig design on it?

I believe it could hold about 3 high density FPGA chips.
The A1000 has a board that is piggy backed and uses a set of header pins. I believe.
The FPGA would be soldered onto a board with pin holes around the perimeter.

Good day.

[AMC258]

Please explain.  I can't tell exactly what you are talking about here.  Do you mean you want to put a Minimig in an A1000, or you want to convert a Minimig to a full A1000, or you want an expansion bus for the Minimig???

[trekiej]

Considering how many pins are on some FPGA chips,  making a daughter card similar to Minimig that would have pins around the perimeter may be useful.  It may solve for a while the multilayer board making approach.  

The older computers like the Altair 8800 had a back plane that connected the processor board to memory,video, etc.
Those board where at 90 degrees to the back plane. These would be parallel to fit into amiga cases.
I do not know what would be needed on the back plane to support the daughter cards.  I guess it would be up to the designer.
Making one to fit into old Amigas would be interesting.

[FrenchShark]

Hello,

I plan to fit a stratix II dev board into an A1200.
This week, I am going to replace the 2MB SRAM chip by a 8MB one so I can get 8MB of 32-bit chip RAM running at 64 times the OCS speed :-D
Then, I have to design a daughter board with all the Amiga specific I/O (RGB, composite, audio, joysticks, keyboard, floppy, parallel and IDE !)

I also have a prototype of a RISC CPU that I might use as a video/audio co-processor. For the moment, it takes 1,600 LEs of my FPGA (out of 60,000...).

From my point of view, the easiest way to get a high quality HW for an expanded minimig is to buy a dev board.
The DE2 has the best feature/price ratio (especially if you can get the student discount). The new DE2 with the Cyclone II EP2C70 is incredible (dual DDR-RAM, dual video input).

Regards,

Frederic

[motrucker]

I would love to know what everyone's smoking in this thread.....     :-)

[trekiej]

Smoking?
How about a ham for Christmas?
lol

How does this sound?
To make a poor man's 4 layer board, use 2 two layer boards.
I do not know yet what to use to insulate the two layers.
The bottom layer could have the mounting holes drilled out larger to allow the board to set lower in the case over the standoffs.  Your project may not need this.
This of course does not have to be an Amiga project.
This maybe nothing new in the circuit board industry.

 

[AMC258]

Put two two-layer boards together and you get a very thick three layer board, not a four layer board.  Three two-layer boards gives you a way too thick four layer board.

You could put a mylar sheet between them though and get what you are trying to get, along with some extraneous capacitance.

[trekiej]

I am not for sure how 2 two-layer boards would become a 3 layer board.  Does one of the copper layers get removed completely during processing?  The mylar I believe could insulate the two copper layers.  I am not saying this is the best way.  I agree it would be thick.

I wish I had acces to .030 inch 2 layer boards.  I feel I would have to make them myself.

[FrenchShark]

Does the mylar resist to soldering temperature ?
I know some pcb prototyping companies have half thickness PCBs but the price difference might offset the price of a 4-layer PCB.

If you have a very thin insulator, you should adapt your traces accordingly ( => very thin trace) to have the right impedance.

By the way I am not smoking anything and I hope my Nios board won't smoke either :-P

[trekiej]

I have found 2 companies so far that sell 1/32 and 1/64 inch single and double sided pc boards.

Has anyone on this thread used Eagle Cad?
Is there a program that you prefer?

Good day.