Delete comment from: Ken Shirriff's blog
I am thinking how many transistors are actually saved by using scale ROM. Well the saving is 3 x 64 = 192 transistors in melody ROM. On the other hand scale ROM itself has 16 x 7 = 112 transistors. But if I add only 16 4-input NAND or NOR in decode logic, 8 transistors for each, I have to add additional 128 transistors. Now I already have 192 saved transistors vs 240 additional and I ignore rest of the additional logic needed. Not mentioning less regular design and lower transistor density. It seems there was no saving at all.
Jan 1, 2022, 9:32:13 PM
Posted to Reverse-engineering a tiny 1980s chip that plays Christmas tunes