so i found some old pc gaming magazines from the mid-late 90s at value village today and
oh my GOD
i don’t know about you but i wanna play me some space dude
Wu-Tang is for the children!
The best revenge is to be unlike him who performed the injury.
Marcus Aurelius (via lazyyogi)
Dumping the ROMs
On the back of the VT100 is a tall access panel affixed by four screws. Behind it is a card cage containing the Basic VT100 video card. Once the keyboard is unplugged, the video card can be easily removed by carefully pulling it out of its slot.
This VT100 has the Advanced Video Option (AVO) board installed. That’s the small daughterboard you can see on top of the main board in the third picture. The VT100 ROMs are in sockets beneath the AVO board.
The VT100 shipped in two variants: with a single 8Kx8 24-DIP ROM or with 4 2Kx8 24-DIP ROMs. We have the 4 2Kx8 variant. Here’s where it gets a little loopy: in the technical manual, ROM 0 is towards the middle of the board and ROM 3 is towards the edge. Confusingly, the order of the ROM chips on my (working) board was reversed! I was chalking it up to an error in the technical manual, but a few failed attempts to dump one of the ROMs later I suspected something was up. That’s when I noticed the schematic above.
Rather than use a demultiplexer to select the correct ROM chip based on the high two bits of the address, the DEC engineers decided to essentially handle the demuxing in the individual ROMs themselves, with this weird three-line chip select mechanism. It’s a really clever solution, since
- it saves the cost of another demultiplexer chip,
- you can drop in a single 8Kx8 ROM (more on that later) instead of four 2Kx8 ROMs in a later revision without having to alter the board layout, and
- you can install the ROMs in any order you want, and the thing will still work.
Now that I understood how the chip select mechanism worked, I modified my dumper to set the CS1..3 lines correctly, dumped all four 2K ROMs, and assembled them into an 8K image.
Next up: disassembly.
To you alone it is given to know the truth about the gods and deities of the sky…The innermost groves of far-off forests are your abodes. And it is you who say that the shades of the dead seek not the silent land of Erebus and the pale halls of Pluto; rather, you tell us that the same spirit has a body again elsewhere, and that death, if what you sing is true, is but the mid-point of long life.
Lucan Pharsalia c.60CE (via stellanemus)
“Once you let people know anything about what you think, that’s it, you’re dead. Then they’ll be jumping about in your mind, taking things out, holding them up to the light and killing them, yes, killing them, because thoughts are supposed to stay and grow in quiet, dark places, like butterflies in cocoons.”
― Helen Oyeyemi, The Icarus Girl