Tuesday, January 31, 2017

Running 40 year old software

It is amazing to be able to run software (code) that is 40 years old. I was able to run code that I have not run since I was a kid in 1978 on my then recently built Netronics ELF kit.

I have mentioned this emulator before --> http://www.elf-emulation.com/ but recently decided to try to get it to run the PIXIE code the was published in Popular Electronic July 1977 issue. The emulator for the COSMAC 1802 CPU can also emulate the CDP1861 PIXIE video chip too. I used the original articles code and created a rom file and loaded it in the emulator and it worked! Below is the image generated and what was display on the TV of the original ELF. The random looking blocks at the top of the image are actually the code that is running to display the image. The PIXIE chip is displaying 256 bytes of memory arranged 8 bytes wide by 32 bytes high, with each spot or pixel being 1 bit. Hence a 64 pixel by 256 pixel image. The ELF only had 256 bytes of memory. If you had more memory you could assign a specific memory space just for the video image and another for the code.

elf.exe -r pixie.rom -a -1861

I remember keying that code into the ELF II above via the hex keypad and being totally amazed when I saw it on my TV I had connected. I then later devised my only images to be displayed.

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