Hi All,
I started a few months ago gathering all the components to recreate an Apple I. I know it’s a bit of a crazy project, and every day it becomes more challenging and expensive to find the necessary parts, but I’m determined to keep going.
One of the most difficult components to source seems to be the memory chips. The only ones I’ve managed to find at a reasonable price are the Mostek MK4027N-4. However, I’ve come across various discussions about speed and cycle time compatibility. Can anyone confirm if this chip is suitable for use in an Apple I? If it is, would I need to modify or adjust anything to make it work?
thanks a lot for suppor
regards
Guido
Mostek MK4027N-4 works perfectly in the Apple-1 replica. As well as -2 and -3. The only thing to consider is that these are faster chips than the original Mostek 4096. So you'll have to reduce the 27K resistor a bit by replacing it with 20-22K. Or, to keep the authentic look of your assembly, you can keep the 27K but solder a 100K resistor parallel to it at the bottom of the board. Either way, you should get T~ 480nS on pin 13 of 74123.
FB_IMG_1736954474126.jpg
To be honest, I didn't notice any difference in performance, even when I mixed up all the Mostek I had on the board for fun.
yeap
ok thanks for all