Works fine as a drop-in replacement for the AT29C256. These work great with the G1, G3, F1, etc. This is the max size for a 28-pin chip. When the C1 isn't big enough, such as Ford EEC-IV applications or later-model TBI GM systems, this chip will do the trick. 90ns flash drop-in replacement for 27C512 EPROMs. Make sure your programmer supports it, there's a funky programming erase voltage required (BURN1, APU1, or PocketProgrammer2 should be fine, APS1 is not). Works fine with 1227165, 1227730, and other similar ECMs. If your car normally takes a 27C128, 27C256, or 27C512, these should work for you. Just adjust the 'Start of Device' value when programming. (For 27C128 original, set to C000 hex. For 27C256 original, set to 8000 hex.)
Due to very low supplies, we must limit orders to no more than 10 chips per customer.