Hi Most 4164's are 7 bit but look out for TI and some Samsung chips that are labled as 4164's but are actually 8 bit refresh. There is no easy way to tell by the part number. Even the Samsung ones are only different by the date code and rev letters!! The easiest way I've found to check is to put them in a Z80 system that uses the Z80's refresh address generator. If it holds data it is 7 bit. Dwight