Minimig PCB run - interest thread

[JimS]

freqmax wrote:
ATA (IDE), ZorroII, SCSI all wants a large number of I/O pins. There a currently 4 remaining. A few more possible by reusing boot configuration pins. Getting larger fpga means BGA and that is a path you don't want to go.

I was looking at the schematics earlier toady. It might be possible to pick up 5 extra fpga pins by multiplexing the joystick ports. This would require adding another chip to the board though.

Personally, I don't see the need for PCI, Zorro, or SCSI. It would fun to add USB and MP3 to the SPI ports, though. Hook up a Vinculum Vmusic board and you've hot both.

[JimS]

freqmax wrote:
As for replacing the cpu, it's mainly a question about weather the number available fpga i/o's are enough.

I believe you'll also have to deal with the fact that other 68k family CPUs use 5v I/O while the FPGA uses 3.3V.

As to IDE support... has anyone considered SATA? It needs fewer pins.


BTW, I'm interested in an assembled board, if the ballpark cost mentioned earlier can be met. At my age, I can barely see those 0.5mm pins, let alone solder them. ;-)

[JimS]

freqmax wrote:
The datasheet for MC68040 I looked at says Vcc 0V-7V. So I guess 3.3V operation is ok. S-ATA is nice but requires either an transceiver/PHY => more pins. Or an FPGA with S-ATA port => Virtex-4 FX => Significantly more cost & use of bga packages.

Ahh.... it's always something. ;-) I'd *guess* that if you ran a 68040 at 3.3V, you'd need to roll down the clock speed to get reliable operation. But that's just a guess on my part. I seem to recall Dennis saying he picked this particular CPU because it was 3.3V and compatible with the FPGA. Be great if faster CPUs were an option.... either with an actual CPU, or another FPGA running a 68K core.

The folks at Schmartboard have announced BGA versions of their prototype boards. Last time I looked it wasn't shipping yet...

For the USB interface, how about the Vinculum chip? It has it's own CPU that runs a USB host stack. Interface is via either a UART, SPI or FIFO. I believe there's a spare SPI on the Minimig...

[JimS]

I was just on the schmartboard web site t'other day. They have a prototyping board for BGA chips up to 400 pins. They claim it can be hand-soldered.

[JimS]

alexh wrote:
Impossible, they must have a BGA rework station.

Well, they do say that it works better with a reflow oven. However, they do show instructions for doing it by hand.

[JimS]

freqmax wrote:
Belial6:
Well but HOW do you solder it. Because you won't be getting the soldering iron between the chip and the pcb.

The way I understood it, all of the solder balls are on via holes, so you can solder it from the underside of the board.