Replica and Emulators(was: Alto II (was Re: PDP-8 prices))

Depends on the parts you gan get for low/free. But forget about the dream of using old telephone parts, especialy relays - this time is gone for mor than 20 years - there are no more old scraped exchanges to get 600 relays (and even if, they would be most likely EWS type machines, their relais aren't just single orphans, but rather high integratet mechanical structures, where it is almost impossible to extract a single relay). You have to buy new ones (or beeing lucky to find enough high quality pcs. at a surplus store). And you cant go for the 4 Mark types with one switch, since the Z3 uses often more than one. Also it's a must to use socketed types, for easy exchange (that would also simplyfy the design) - an exception to this might be if you want to build it as small as possible - but the relays needed in this case might cost even more. At a number of some 600 relays and sockets I assume an average price of an relay at DM 10 plus DM 4 per socket. That gives 14 Mark (or USD 8) per installed relay - assume you use an Euro card style (within a 19" rack) you might end up with 4 or maybe 6 relays per card (4 if you use 90 degree socket to reduce card height - or if you want to use a low density to keep it easy to wire - or 6 if you go for the maximum - a 4 relay per card design will result in about half the heigh per card as a 6 relay per card design, so the whole computer will be 25% smaler). This means you need some 150 PCB boards at, lets say 10 Mark each - with an aprobiate connector for 10 Mark each. To mopunt them, another connector is needed in the rack at 14 Mark each, eding up with 34 Mark per board (or 90 Mark including the relays). Now we have 13500 Mark (or ~8000 USD) and thats only the PCBs, relays, sockets and connectors - I assume the rack(s), card mountng, power supply(s) and small parts (like diodes, resistors and wireing) are just for free. Of course you can go and collect relays wherever you find them and end up with hundreds of different types and dozends of needed voltage levels etc. not to mention that this beast will need _a lot_ more room (usinge the design describen above we need at _least_ one full height rack, but maybe two) and dont forget the problem of different kinds of mounting for the relays. Gruss H. Step aside, and wait for a real stunning idea, soon to arive (no comment). -- Ich denke, also bin ich, also gut HRK