build the same processor with the unused instructions removed it would be smaller and thus less expensive, while if one instead used those transistors to improve performance instead of decoding instructions that would not be used, a faster processor was possible. The RISC concept was to take advantage of both of these, producing a CPU that was the same level of complexity as the 68000, but much faster. To do this, RISC concentrated on adding many more registers, small bits of memory holding temporary values that can be accessed very rapidly. This contrasts with normal main memory, which might take several cycles to access. By providing more registers, and making sure the compilers actually used them, programs should run much faster. Additionally, the speed of the processor would be more closely defined by its clock speed, because less of its time would be spent waiting for memory accesses. Transistor for transistor, a RISC design would outperform a conventional CPU, hopefully by a lot. On the downside, the instructions being removed were generally performing several "sub-instructions". For instance, the ADD instruction of a traditional design would generally come in several flavours, one that added the numbers in two registers and placed it in a third, another that added numbers found in main memory and put the result in a register, etc. The RISC designs, on the other hand, included only a single flavour of any particular instruction, the ADD, for instance, would always use registers for all operands. This forced the programmer to write additional instructions to load the values from memory, if needed, making a RISC program "less dense". In the era of expensive memory this was a real concern, notably because memory was also much slower than the CPU. Since a RISC design's ADD would actually require four instructions (two loads, an add, and a save), the machine would have to do much more memory access to read the extra instructions, potentially slowing it down considerably. This was offset to some degree by the fact that the new designs used what was then a very large instruction word of 32-bits, allowing small constants to be folded directly into the instruction instead of having to be loaded separately. Additionally, the results of one operation are often used soon after by another, so by skipping the write to memory and storing the result in a register, the program did not end