Date   : Thu, 11 Aug 2005 19:55:32 +0100
From   : Phil Blundell <philb@...>
Subject: Re: 80186 co-pro

On Tue, 2005-08-09 at 23:37 +0100, Rob wrote:
> Actually, in my quest to find a cheap 6502 2P, I was last night poring over 
> the circuit diagram & rom dumps of the acorn 6502 trying to decide if I 
> could build one myself, but instead based on 6502+static ram+eeprom+??as 
> tube and had decided I probably could, but it would cost me about that much 
> in parts, including a prototype board to build it on first, and I'd still 
> need to find a tube ULA ..  

Yeah, it wouldn't make much economic sense to do a direct clone of the
6502 co-processor nowadays.  The DRAM adds a lot of complexity, and I
suspect those little RAMs are more expensive to buy (if you can get them
at all) than the equivalent amount of SRAM.

As far as the Tube ULA goes, my original plan was to use something like
an XC9500 CPLD.  But, having looked at the number of registers involved,
it seems like a CPLD solution would start to get rather expensive; a
small FPGA would probably be a better bet.

p.