Can 2149 ram be used as 2148 ram? i installed (2) chips of 2149 in my galaga in repacement for the (8) 2147's and now i'm getting really bad vertical lines thru everything.
Yes, the 2149 and 2148 should be interchangeable. The difference is that 2149 does not have a low-power mode like the 2148 (not relevant for this application). What speed grade did you use? That strikes me as the most likely culprit. Regardless of the type, it needs to be fast enough. Unfortunately I cannot find what Galaga requires offhand. My 2147's don't have an obvious speed rating and the schematics don't appear to list one.
2114, 2148 and 2149 are all interchangeable from a pinout standpoint. The main difference is that the 2114 is much slower (100-250ns access times) whereas the 2148/2149 are much faster (35-70 ns). The 2148 and 2149 differ in the that the 2148 has a low power mode and the 2149 does not (which makes the 2149 chip select access time about half that of the 2148). If a design calls for a 2148/2149, it needs the speed of that part. While a 2114 will work from a pinout standpoint, the speed difference will likely cause problems.
In the case of Galaga, it uses 2147s by default and the slowest 2147 (70ns) is significantly faster than than the fastest 2114 (100ns) (and the fastest 2147 is like 4X faster than the slowest 2114). Thus, I very much doubt that substituting a 2114 would be successful.
Can 2149 ram be used as 2148 ram? i installed (2) chips of 2149 in my galaga in repacement for the (8) 2147's and now i'm getting really bad vertical lines thru everything.