Apple 1 Reproduction

I like to build electronics and love vintage computers (hence all these pages). These are machines from when I was growing up and were out of my reach. But I can now build them and demo them at places like VCF East. The MARCH chapter and my makerspace Computer Deconstruction Lab are on same the InfoAge campus at Camp Evans in Wall NJ.

So all the trouble began when I wanted to build an Apple I reproduction with an MC6800. I found a nice set of blank PCBs on Ebay and ordered two, one for the 6502 and one for the 6800. If I had checked on the cost of building these boards before hand I would have probably not done it. Some of the discontinued chips are $100+ per chip (Yikes!). Well I did find a sorta working Apple I reproduction on EBay. So I bid never really expecting to win. Well I did. I've now diagnosed and repaired the Apple by replacing a bad 2519 with an SMT replacement board. It works great! I will play with the Apple I later.

Why?

Well I really like what Woz did. While the video section isn't too from a dumb terminal it is unique in that it is built into the main computer. The design is influenced by Don Lancaster's TV Type Writer. Woz squeezed a lot into that computer and came away with something that looked more like what we would later see as a computer. A year later Radio Shack wold release the Model 1 for about $600 (slightly less than $3200 today 2025). Woz's ROM monitor was 256 bytes long and you could examine memory, write memory, execute a program in memory. The most basic of command but enough to get started. Today we have point and click, much simplier but so much more complex to code. Don't get me wrong, things are faster and easier today but we are so removed from the bare metal computing. For most that's perfect but for engineer type we want to poke around under the hood. :-)

For now I'll post a few quick pictures and clean up these pages when I get more time

Notes

As usual, a work in progress with some notes I put together to better understand the Apple I.

Apple 1 video

Refresh

Four out of every 65 clock cycles is dedicated to memory refresh. At the starat of a refesh cycle (150ns after leading edge of Ph0), RF goes low, and remains low for one clock cycle. Ph2 is inhibited during a refresh cycle, and the processor is held on Ph0 (it's inactive state). Dynamic memories, which must clock during refresh cycles, should derive their clcok from Ph0, which is equivalent to Ph2, except that it continues during a refresh cycle. Devices such as PIAs, will not be affected by a refresh cycle, since they react to Ph2 only. Refer to Apple "Tech Notes" for a variety of interfacing examples.

Equates

Pictures

I know the monitor is a bit whack. Another thing to work on. The desk is my work bench and the TS803 needs the vertical repaired. And the Apple I is sitting on top of the Gimix Ghost whose power supply needs to be reconditioned before testing. The loose papers are from parts orders (more build projects).