Somewhat OT: FPGA Develpment Kits

[Vincent Slyngstad]

From: "Don North" <ak6dn at mindspring.com>
> Vincent Slyngstad wrote:
>> One of the questions I have kicking around (I even bought an XESS
>> board) was: How hard would it be to get a PDP-8 core into an FPGA
>> and arrange the pinout to correspond to the 6100 or 6120?
>>
>> Then it wouldn't be necessary to desolder 6120's from Decmates to
>> get our SBC6120's working :-).
> 
> Getting the logical signals to match would not be that big a deal; the 
> larger problem would be getting a compatible form factor. I retargeted 
> my PDP8 above to a XC2S30 and it occupies about 75% of the device. In 
> a CS144 (small 0.8mm pitch BGA) one could probably make a DIP40 plugin 
> carrier that was pin compatible to either the 6100 or 6120 parts.

Hmm...BGA...ick :-).  We only need about 40 pins for this application.  
Does anyone make a device with a smaller pincount?  A nice solderable 
64-pin qfp perhaps?

> None of these devices use 5V supplies, they are all 1.8V~3.3V at most. 
> The power supply issue can be solved by a small linear regulator, but 
> I/O level compatibility is a stickier problem.

I was thinking a 3.3v device with resistors in the input paths to keep 
them within range.  The outputs would probably be acceptable as-is.

> Anyway, it is an interesting problem, probably solvable given more 
> thought and research. However, I suspect any low volume solution 
> will still be more costly than just tracking down old IM6100 ICs 
> for $10-$20. Not nearly as much fun, tho.

True, but figuring out how to one-off a replacement for a 6120 seems 
a worthy project.  Also, I think the cost-benefit equation will 
continue to shift, as old parts get more expensive, and new ones 
(hopefully) don't :-).

    Vince