31. This became less important when index registers and debug, as well as being inefficient under modern processor pipelining and caching schemes. 32. Additional operation codes were provided for options, such as floating point, core storage, index registers and additional I / O devices. 33. Four of the arithmetic registers are also index registers ( the sets overlap index register X12 is arithmetic register A0 ). 34. In addition to two accumulators, the DASK had three index registers , which could be used to modify the address of most instructions. 35. Parameters might be coded in-line ( immediately following the BSI instruction ) or might be placed in index registers XR1 and XR2. 36. The CPU had 15 index registers , a four-bit field ( x ) allowed selection of one index register as the base register. 37. Four of the arithmetic registers are also index registers ( the sets overlap index register X12 is arithmetic register A0 ). 38. The 16-bit 6800 index register was split into two 8-bit registers and these registers operate in the " true " indexing mode. 39. The IBM 700 / 7000 series scientific machines use sign / magnitude notation, except for the index registers which are two's complement. 40. The CPU had 15 index registers, a four-bit field ( x ) allowed selection of one index register as the base register.
