addressing only the comment quoted below . . . Really, Tony, I think you overemphasize the importance of the individual user to the semiconductor manufacturers. The level of competition for the FPGA business has escalated to where the development software, previously costing several K-bucks US, now costs as little as $100, and, in the case of ALTERA, is quite free. Now, that's not the complete package with all the bells and whistles, but it's enough to build a device from start to finish. I really doubt that it would turn out to be illegal to take the old 11-70 or whatever schematic and essentially clone it in an FPGA, but I doubt a clever rebuilder would want to do that anyway. It might be either equally good in the end product to build the thing so it's thriftier than the TTL design would be, yet still a bit faster, or so it's quite a bit faster and perhaps not quite the same. It doesn't have to be identical to run the same code. The technology in FPGA's these days is such that it enables devices to operate between 10 and 50 times the speed of the old TTL logic designed in the '70's. That doesn't mean you can take a '70's design and "transliterate" it and make it run lots faster, though that is conceivable. What it does mean is, similarly to translating poetry from one language to another, logical constructs can be ported from one technology to the other, changing the outward and physical details of the circuitry, yet preserving the upper-level sense of the logic in such a way that it capitalizes on the available enhancements, thereby yielding a product which is quite different way at MUCH greater speed, or MUCH lower complexity, and, hopefully lower cost. Once you've translated a poem, you've done the same work as the poet, more, in fact, yet you've created nothing new. OTOH, in the case of the computer, redesigned to capitalize on new technology, I believe you could argue that it is, indeed, something quite new. If it were to be generated for, say , a XILINX part of the 5200 series, it would not necessarily be very costly, nor would it be difficult once one has the original print set as crib sheets. What's more, it would potentially be so much faster than the original, and take up so much less space, e.g. a 2" square package, you could build the MMU into it and interface it directly to the DRAMs, maybe adding a circuit to copy the ROM code into RAM during its boot. Schematic entry would be the easiest way to clone the prints, but HDL is considered by many to be the best way to implement an architecture, the behavior of which is well defined and understood. If you build your device in VHDL or VERILOG, it is inherently portable, since both XILINX and Altera, among others, support both. Building a device like this in several parts merely ups the cost, since resources are consumed by the interconnection between them. Time is used up in the interconnections as well, so performance would be lower. When all is said and done, the single FPGA is the "right" notion. I don't think the FPGA makers would care if you use their parts to craft a device. If you have the HDL code, nearly any distributor will provide you access to the resources to implement it in a product they sell, provided you buy the parts from them. They cost a few dollars in small quantity, but if you say the right "things" when approaching them, and seem sufficiently eccentric, they'll treat you right. Dick -----Original Message----- From: Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt; To: Discussion re-collecting of classic computers &lt;classiccmp(a)u.washington.edu&gt; Date: Thursday, August 26, 1999 4:08 PM Subject: Re: PDP era and a question <snip> years. would anyone them *BSD.