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I decided to switch from Pluggy Reloaded to a slightly stripped down version of Marcel's expansion board (still untested). It has 2 SPI ports; with one connected to a board-mounted SD card and the other to a header. There are a couple of mounting holes either side of the RAM for an expansion card. This could connect to the SPI1 header, or if you wanted more options then the onboard expander can be bypassed by jumpers (as shown) and you can go directly to the RAM socket. This way one of the other expander designs could be plugged in (although you are starting from a 32-pin DIP rather than the Gigatron 28-pin).
. Note the original EDI 1M bit static RAM chip - date code 1994 but originally released in 1989
![Cool 8-)](./images/smilies/icon_cool.gif)
The board is wired for 6-bit audio, so there are only two blinken lights available and these are connected to a single bi-color LED. There is an additional 74F157 on board and switch to select between the standard 64-color "low-res" mode and an 8-color hi-res mode. One of the (possible) design goals of the board is to support CP/M as discussed in this post by Marcel. The board is using F-series chips and runs fine at 12.5Mz.
The main delta between the Gigatron and Novatron is the use of GALs to replace the diode ROMs and ALU multiplexers. The expansion also uses a GAL but this only implements a few gates from the original expansion card. I've attached the schematic, but warning! Everything is crammed in to just 3 pages, so it might be a bit hard to follow.
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I'll be demoing this at VCF Midwest next month with the plan to offer a kit in another month or two. I plan to include a Famicom controller but just realized you might need to yank out the ATtiny85 to make this work... still a few things to figure out here
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)