here are parts compatible with 7611's 256*4 +------+ A6 |1 16| Vcc A5 |2 15| A7 A4 |3 14| CE2/ A3 |4 13| CE1/ A0 |5 12| O1 A1 |6 11| O2 A2 |7 10| O3 GND|8 9| O4 +------+ Signetics MMI TI Harris Raytheon AMD National Intel --------- --- -- ------ -------- --- -------- ----- TS 82S129 (50ns) 6301-1 24S10 7611-5 29661 27S21 74S287 3621 82S129A(27ns) 63S141 - 7611A - 27S21A - - Intersil Fujitsu -------- ------- 7052