HelenOS sources
EGA_INDEX_REG 467 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0a);
EGA_INDEX_REG 469 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0a);
EGA_INDEX_REG 477 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0e);
EGA_INDEX_REG 480 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0f);
EGA_INDEX_REG 489 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0e);
EGA_INDEX_REG 491 kernel/genarch/src/drivers/ega/ega.c pio_write_8(instance->base + EGA_INDEX_REG, 0x0f);
HelenOS homepage, sources at GitHub