Keith wrote:
Michael J. Mahon wrote:Keith wrote:It's so easy to do, you might as well, assuming you've got room for it in the FGPA (two processor cores is likely to eat a lot of room) MattBased on my experience with the Xilinx Spartan XC3S1000 (Digilent Spartan-3 Board) I would guess that you could just about squeeze an entire AppleCrate onto one. And the communications channel could be much faster than that used on an AppleCrate. Don't know if anyone would be interested in that or not. You could probably clock them faster than an AppleCrate too, but maybe not much faster since you would probably be time domain multiplexing the SRAM to provide enough memory to the CPU cores.Cool! ;-) Of course, with both on-chip and shared memory communication possible, the entire networking premise of AppleCrate would be unneeded. A much closer coupling should be supported--closer to SMP. It's fun to think about hi-tech approaches to lo-tech problems! ;-) -michael Parallel computing for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."How much of an Apple II would one need to emulate in order to get the client-side of AppleCrate working? Assume that it would use the same networking as your box is using, and not some new invention. It would seem that you could leave out a lot of the logic that makes an Apple II and Apple II. Is this correct? If it's not too bad I might try to do it for fun.
The only thing required to participate in a NadaNet network (which is what AppleCrate machines do) is the ability to bit-bang the serial network line at 94-95 Apple cycles per byte (8 cycles per bit) and sense them if receiving (while maintaining phase lock within 3 cycles). The rigidity of the timing requirements makes it hard to do in any environment in which interrupts can cause jitter of more than a microsecond per byte, like PCs and Macs, unless interrupts can be disabled for the duration of a packet, which could be nearly 25 milliseconds (which is also problematic for PCs and Macs). There should be no problem at all meeting these requirements using a microcontroller or hardware. Of course, the protocols for actually using the network for something would also need to be implemented, and they currently exist only as 6502 code, optionally invoked by ampersand routines in Applesoft. -michael Parallel computing for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."