This is part four of my blog posts on my 286 basic system build. At this stage, PS/2 keyboard input, interrupts, and LCD output are working.

Part 1: 80286 Build #2 (Intel Basic System Configuration)

Part 2: 80286 Build #2 (Intel Basic System Configuration), Part 2

Part 3: 80286 Build #2 (Intel Basic System Configuration), Part 3

Code used in the above video: x86/g1_20221208.asm at main · rehsd/x86 (github.com).

Code used in the above video: x86/g1_20221210.asm at main · rehsd/x86 · GitHub.

I have swapped out the larger flash memory (ROM) ICs with SST39SF010A ICs. Previously, I was using a larger capacity SST39SF040A with the upper address lines tied to ground. Also, I have swapped out the 8255 PPIs with 82C55 PPIs. With this change, the full system is drawing approximately 700 mA (excludes the two Arduinos and OLE screen which are powered from the PC's USB).

I removed the LED hat from the 80286 and added internal data bus pull-up resistors (3.3K). The system is now running with an 8 MHz processor clock!