Re: [N8VEM: 13969] Re: 68030 SBC project ideas

[Alan Hightower <al...@alanlee.org>]

ATF1504 and ATF1508 CPLDs are still the most value for through hole 5V PLCC 44/84s.  However their availability is very volatile.  You can build a parallel port programmer with a '245 and some passives.

Even a series of 22v10s might make sense to cut down on discrete logic.  They are readily available everywhere, come in 5V DIP-24s, and can be programmed in most ROM burners.

The DRAM controller is the hardest component.  If you went with a larger PLD like a Lattice MachXO2, you could easily put it there.  However such larger CPLDs and FPGAs only come in SMT.  If it came to that though, might as well put the VGA controller and SD card there too.  Could easily fit all three and more in a 2000-4000 LUT XO2.  For low end devices, nothing beats an XO2 on features.

For propeller interfacing in 5V though hole designs, I've suggested before but it's worth repeating.. IDT7200 series FIFOs offer a way you can decouple the bus and propeller operation - and even pipeline it.  Place two back to back for a bidirectional FIFO,use the empty strobe in interrupt generation for both sides, the full strobe to add wait states, and implement a simple command/response protocol.

And you can easily fit a complex CPU like a 68040 in a mid sized FPGA.  You can even implement a lot of relatively modern CPUs (like P3/P4s) in top end $20K FPGAs like Stratix 9s. But if one were to do that, forget building a special board.  You can do that in existing eval boards like a DE2.

-Alan

Sent from my iPad

On Jun 24, 2012, at 10:37 AM, "Andrew Lynch" <LYN...@YAHOO.COM> wrote:

>> 
>> I'd guess that, if we were creating a 68k system, that we'd be targeting
> either
>> Linux/m68k or Net/OpenBSD m68k.  And, between the two, I'd assume that
>> the *BSDs would be easier, given their lack of assumption that a 68k
> machine
>> is a Macintosh.
>> 
>> The other 68k OSes out there that I'm familiar with are hp-ux and SunOS,
> and
>> they're both _very_ architecture-specific.
>> 
>> I think that a fairly quick 16 Mhz+ 68040 SBC with reasonable RAM would be
>> very cool.  It'd be quite a hackable system.
>> 
>> And, I second Sergey's suggestion that there be something of a frame
> buffer.
>> It'd be neat to be able to do at least console fonts.
>> 
>> - Alex
>> 
> 
> Hi Alex!  Thanks!  I am assuming the NetBSD-68K would be the starting OS
> after a debug monitor as it is probably the most portable of the Un*x like
> operating systems.  HP-UX, SunOS, and Solaris are probably not realistic but
> Linux-68K may very well be obtainable.
> 
> Thanks and have a nice day!
> 
> Andrew Lynch
> 
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