Have a look here: http://www.ourcomputerheritage.org/ Around 40 machines from 1950 to 66. 17 machines from Elliott, 11 Ferranti, 3 Leo, 4 English Electric, 2 BTM and 5 ICT. For me the Elliott 900/920 series is particularly interesting, 4 op- code bits, a B line modifier and 13 address bits. I worked on compilers for this before writing one for the Zilog Z8001 to replace the 920 ATC. The language was Coral 66, and Algol 60 derivative for real time computing. The 900 had no OR,XOR or NOT instructions, but it did have a negate and add instruction, and if you had a word in memory holding the constant -1, then a negate and add -1 could be used to do a NOT. From this and the built in AND instruction could be built the other bitwise logic operations. There is no subtract operation either which meant that the order of evaluation had to be changed around within the compiler to use the negate and add instead. The other conditional jumps had to be constructed from jump zero, jump negative and unconditional jump. Increment but no decrement. No stack, no immediate operands, an accumulator (A) and a right side extension (Q) and a B register which could be used to modify any instruction allowing access to all 256k memory words (though only 128k of program). No carry flag so multi word arithmetic was hard work, including software floating point, thankfully built into hardware in the 920ATC. My other personal interest is the ICT 1301 which is memorable for having no program counter, in being 4 bit parallel, 12 digits serial, having no indexing instructions and being programmable purely in decimal. Even core memory is decimal, if you try to execute a non decimal digit the machine would stop at instruction fetch. If you directly hand key an instruction with a non decimal digit in the address field, the core memory will not respond (the CPU sees a zero) and stop the machine with a parity error unless parity checking has been turned off.