20150710 - Inspiration Reboot


Quite inspired by the insane one still or video per day at beeple.tumblr.com. Attempting to get back in the grove of consistently taking a small amount of non-work time every day to reboot fun projects. I'm on week 2 now of probably a three month process of healing from a torn lower back, sitting in front of a computer is now low enough pain to have fun again...

1536
Setting a new 1536-byte (3x 512-byte sector) constraint for a bootloader + source interpreter which brings up a PC in 64-bit long-mode with a nice 8x8 pix VGA font and with 30720-bytes (60 sectors, to fill out one track) of source text for editor and USB driver. USB providing thumb drive access to load in more stuff. Have 1st sector bringing up VGA and long mode, 2nd sector with 64-character font, and last 512-byte sector currently in progress as the interpreter. Went full circle back to something slow, but dead simple: interpreter works on bytes as input. The following selection of characters appends simultaneously to a 60-bit 10 6-bit/char word string, and a 64-bit number,

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ#$@!+*-^&|=?<>_

Then giving a "color forth tag" like meaning to another fixed set of characters,

~ - Negate the 64-bit number.
. - Lookup word in dictionary, and push 64-bit value onto data stack.
, - Push 64-bit number on data stack.
: - Lookup word in dictionary, pop 64-bit value from data stack to word.
; - Write 32-bit number at compile position.
" - Lookup word in dictionary, interpret the string at address stored in word.
[ - Lookup word in dictionary, store compile position in word, append string from [ to ] compile position.
] - When un-matched with ], this ends interpretation via RET.
\ - Ignore text until the next \.
` - Lookup word in dictionary, call to address stored in word.

Those set of characters replace the "space" character in forth, and work like a post-fix tag working on either the string or number just parsed from input. The set of tags is minimal but flexible enough to build up a forth style macro language assembler, with everything defined in the source itself. More on this next time. One nice side effect of post-fix tags is that syntax highlight is trivial by reading characters backwards starting at the end of the block.

Sony Wega CRT HDTVs
The old Wega CRT HDTVs work quite well. They apparently are nearly fixed frequency 1080 interlaced with around 540 lines (or fields) per ~60 Hz frame, and unlike prior NTSC CRT TVs, they seem to not do any real progressive scanning. Taking a working 1080i modeline and converting it to 540p and driving the CRT results in the Wega initiating a "mode-reset" when it doesn't see the interlaced fields for the 2nd frame. However 480p modes do work (perhaps with an internal conversion to 1080i). Given that 1080i modes are totally useless as the 60Hz interlace flicker is horrible, and 540p won't work, these HDTVs should be complete garbage. However 720p works awesome as the TV's processing to re-sample to 1080i does not flicker any worse than 60Hz already does. In theory the even and odd fields (in alternating frames) share around 75% of an input line (540/720), and likely more if the re-sampling has some low-pass filtering. Drop in a PS4 game which has aliasing problems, and the CRT HDTV works like magic. These late model "hi-scan" Wega CRTs only had roughly 853 pixel width aperture grille: 853x540 from what was a 1920x1080 render is a good amount of super-sampling...