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45

Very simple: Because there was room for an address and it improves performance a lot. Or as the manual puts it: It is important, however, for the programmer to realize that the simplest method of programming (using sequential drum location for succeeding instructions) causes the machine to waste a large amount of time waiting and searching. To start with,...


39

I will just explain what a bit is. It's a binary digit. 0 is numerically zero, 1 is numerically one. If you want to add 1 and 1, in binary it overflows. the result is 0, and a carry out. As you understand, other arithmetic operations can be done on bits. They takes a fair bit of logic to implement. Binary is positional. That means that a 1 which is 4 places ...


20

Quibbling about the right meaning of "bit" aside, some advantages of the 2-of-7 biquinary representation are: Simpler circuits. In a quinary adder circuit, the output of each of the 5 output lines becomes just a 5-way OR of binary ANDs of input lines. To implement this with primitive logic building blocks such as resistor-transistor-logic (or its vacuum-...


10

If your primary memory is not random access, in the sense that at any instant some addressed words will take longer than others to be read, then you can potentially improve performance by having each instruction specify where the next instruction is located. The programmer is then coerced to figuring out where that next instruction ought to be. This ...


9

Yes, it WAS due to the fact that with a rotating drum memory, you wanted the next instruction to be at a location that was just about to come under the read/write heads rather than in the next sequential location, where it could take a full revolution of the drum to be able to read the instruction. All was not lost for the programmer, however. The 650 came ...


5

How many logic gates did the IBM 650 have? It's a rather useless question. When is a gate a gate? Is a wired-OR a gate? Does a 38-input-OR, used to create a zero condition count as much as a two-input? Using a gate count does, if at all, only make sense for machines only build from diskrete gates. I'm used to measuring the complexity of a CPU by ...


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