the output indicates that an address in the adapter matches the one received from the ring in the destination address field of the frame as can be seen from this example any 12 bit address presented to the ram could yield the same result that is the da2 bit could be on therefore any da address within the 4k region could provide the match qualification this is what is considered address indexing it should be noted that by using the cam and the external ram the address range available in the adapter is greatly increased it should also be noted that the microprocessor via setting appropriate bits in one of its control register allows the system user the ability to turn on none any or all of the external options i e index ram cam used in the arf fig1 shows a section of the index ram with addresses and appropriate bit settings this table is helpful in understanding the structure of the index ram each element in the index ram is made up of one base register and an associated array of bits each bit in the array represents an individual address in order to calculate the group address value corresponding to an individual bit the bit offset labeled 34 unused 34 is added to the base register value labeled 34 base value 34 the size of the bit.