Monday, May 7, 2012

16K Memory Board is Complete

The 16K memory board is assembled and works fine.  It has two sockets for 8K RAM, EPROM, or EEPROM chips, so you can add any combination of 16K RAM, 16K EPROM/EEPROM, or 8K RAM and 8K EPROM/EEPROM. The EEPROM is writeable but needs to be written with a delay after each write (approximately 1ms depending on the brand of chip used). There are jumpers for each chip to enable writing, so that the EEPROMs can be made read-only, if desired.

Memory Board Installed in Replica 1
I ran the memory test in my JMON monitor on the board stuffed with RAM to verify it.

Running Memory Test on 16K RAM 
So, for example, I could put Applesoft Lite or Enhanced BASIC in ROM (these are too big for the one 8K EEPROM on the Replica 1), or I could use RAM and bring the Replica 1 up to 48KB of contiguous RAM, twelve times what the original Apple 1 had (and then run really big programs).

I only used about half the protoboard, so I could add more circuitry to it later.

Wiring Side of Memory Board
I've put the design files here in case anyone wants to build their own or adapt the design for their own projects.


$@m said...

I like the work you have done for this expansion card for the replica one. I am currently in year 10 and doing an electronics assignemnt, is there any possible chance of a full schematic, as i would like to make your 16k expansion on a stripboard and then attatch it to my replica one. Cheers :)

Jeff Tranter said...

All the design files can be found here:

The only thing missing in the schematic is that it doesn't show the address and data lines hooked up to the corresponding pins of the expansion slot, but that should be straightforward to figure out. If you have any questions, just ask (e-mail is best as I don't always see the comments on this blog right away).