MCL86jr initial results

I just received the MCL86jr board in the mail today and it seems to be working great! I was able to program the FPGA and the attached SPI flash, and then use it to boot the PCjr! I added a DIP adapter so that the pins on this board would not bend and it all fits perfectly under the disk drive carrier!

The initial FPGA code contains the MCL86 CPU core and an 8088 BIU so that it can be used on the PCjr. The next step is to add an SRAM controller so that the additional 512KB can be available to the computer which brings system memory to 640KB. After that I will add registers to provide the ability to run the CPU core as cycle accurate or unlocked mode which allows the PCjr to run significantly faster. I will also add a “fast” SRAM controller which can access the 512KB of memory within 50ns rather than at nearly 1uS as as it would for cycle accurate bus mode.

There is also 32KB of block SRAM in the FPGA which I may use to store PCjr cartridges or the XT-IDE boot image. I will also add the ability to change the computer type-ID to a PC,XT, or AT. This will all be under register control so no jumpers or switches will be needed!

PS: Those red LEDs blink back and forth like KITT from Night-Rider!

Here are a few pictures:

MCL86jr initial results