3 ms·
"Alto Trek (in the Alto's 606×808 portrait ratio screen)" That's higher than I would've expected for the time. That's more than half as many pixels as a Switch
by ClassyJacket 3y ago
"Alto Trek (in the Alto's 606×808 portrait ratio screen)"
That's higher than I would've expected for the time. That's more than half as many pixels as a Switch screen. I was born 11 years after this and I remember using 800x600 as my main desktop resolution.
On that note, anyone know of the reason for the weird resolution of 808x606 instead of a more round number like 600x800?
I can only find this document:
"The display controller handles transfers between the main memory and the CRT. The CRT is a standard 875 line raster-scanned TV monitor, refreshed at 60 fields per second from a bit map in main memory. The CRT contains 606 points horizontally, and 808 points vertically, or 489,648 points total"
https://bitsavers.org/pdf/xerox/alto/Alto_Hardware_Manual_Aug76.pdf https://bitsavers.org/pdf/xerox/alto/Alto_Hardware_Manual_Au...
which explains more detail but doesn't really explain how they arrived at those numbers. I assume it's something to do with vblanking or something but I don't understand it.
- gumby 3y agoI don’t remember exactly but it probably had to do with the logic speed back in those days. The cpu updated screen memory with BitBLT (an operation copied from the PDP-10, hence the name) and the screen was allocated 2/3 (!!) of the memory bus speed. So they ran the logic as fast as they could and that was how many dots they could afford. Remember the Alto was the origin of bitmapped displays.
- helf 3y agoAlto was the /popularization/ of bitmapped displays (In the public mind). Other examples predate it such as the PLATO computer system.