From: Philip.Belben(a)powertech.co.uk <So how about making our own. A tube containing, say, a 4-bit D-type <latch? Make a few in that range and a valve computer becomes almost <manageable! Besides, the smaller it is, the faster you can make it... A four bit latch using valves would require not less than 8 triodes plus buffers. Very hard to do in one envelope... Also tubes had some characteristics that made it very hard to design fast enough logic that distance(size) was a factor. I have a few 7586 and 6ds4/6cw4 nuvistors and they are 0.8" tall and 0.45 dia and make really good rf amplifiers but slow switches. Allison