After I received the original snap shot of John Draper’s Apple II, I asked for and received better images. Here is one of them, showing the unusual Apple II memory arrangement.
If you look closely, you will notice that all the memory banks are double stacked, largely with Signetics 2660 chips. These chips are 4Kx1, compatible with 4096s. This gives this system 24K of memory in 6 banks of 4K on each bank. Though I’ve seen double stacked memory on other systems, occassionally even on production boards, I’ve never seen this on any Apple II. Everyone else, managed to find 16Kx1 DRAMs and used those to expand their systems memmory. Don’t get me wrong, 16K memory chips were not cheap, especially in the early days of the Apple II. In fact for a long time, I ran my original Apple II with 2 banks of 16K and 1 bank of 4K for a total of 36K, which is all I could afford. I do believe John Draper’s approach is truly a unique solution to expanding memory for the Apple II.
What is more remarkable is this article, where John Draper, Capt. Crunch talks about his Apple II.
John mentions his Apple II memory configuration in the second paragraph, “My apple used the cheaper 4k rams and I piggy backed them to get 24k of ram.”
At some point, I plan on reviewing the wiring to see exactly how John wired up the 6 banks of memory.
I have more information on this system to post in later blog entries.