It looks like he's using text mode. IIRC text on VGA (not this) has 4 pages and supports blanking interval stuff by virtue of VGA. 80x25 is 80x9 x 25x16 = 720

It looks like he's using text mode. IIRC text on VGA (not this) has 4 pages and supports blanking interval stuff by virtue of VGA. 80x25 is 80x9 x 25x16 = 720x400. The character maps are actually 8x16 with the right pixel duplicated into the 9th. And in VGA there are two character planes (512 chars total), which explains Norton weird cursor that could go anywhere later copied by FreeBSD and others. It maybe possible to change the character planes to be optimized for drawing. That would be cool.