Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer
I used the Alto at MIT (and for fun when I worked at PARC -- we had more powerful machines by then).There are two other things about the alto that have really stuck in my mind.  First, the whole thing uses only 300 SSI and MSI TTL chips!  No higher order chips (no LSI, much less VLSI).The other is that the bus bandwidth was only 3/2 the screen update rate.  Updating the screen was really important: this was a user-centered, IO-focussed machine which was super radical for its time.  If you wanted to do a lot of computation you could steal cycles from the screen update, causing it to go black (in just the bottom half or so IIRC which I probably don't).Error in the article: I do believe the Alto was the origin of the BITBLT instruction, but it was based on the PDP-10 (PDP-6) block transfer instruction BLT, and the expression blitting was current before the Alto was developed.  In fact PARC had a PDP-10 which was the standard research computer at the time -- homemade as well (clones) because at that time Xerox was in the computer business and wanted PARC to use an SDS.  (Again this is before my time though MAXC was still running when I was there -- with an Alto as its front end!)Also contrary to what the article says, the Alto display was not unusual in being portrait mode -- most glass TTYs (think ADM-3A, Hazeltine, VT-52, and I believe the 3270 as well) were taller than they were wide, like a piece of paper.  The Alto display was unique, as mentioned, by being bitmapped and black on white.  Because of the Alto, bitmapped portrait mode was standard for workstations such as the CADR lisp machines, Bell's BLT terminal, three rivers PERQ, and of course the later PARC computers we used, Dolphins, Dorados (all ECL logic!), Dandelion (sold as the Star).  I remember vividly the first landscape machine I used, the Symbolics 3600 in 1985.  I didn't, and still don't appreciate the wasted space of landscape displays.Three-button mice with the mouse buttons arrayed horizontally was also standard because of the Alto.  The first time I saw the Macintosh mouse in 84 I was shocked: how could someone use only a one-button mouse?  There was a lot of mouse (originally called the "bug") experimentation in the 70s on button count and layout.The microcode of the alto was compatible with the DG nova as that was the computers used at PARC before the Alto was developed (before my time!).edit: forgot to mention the origin of blitting.