VAX graphics

Al Kossow <aek at bitsavers.org> wrote: There is nothing visible in the machine room for a graphic subsystem. It's all in the Unibus box, with just a couple of cables coming out. I'd definitely say no to that. I was working at DEC in 1986. At that time, the VT241 was the hottest thing DEC had, and it could do bitmapped graphics. But let me tell you how long it took to just get a picture uploaded on that terminal, and then we are talking much lower resolution, and fewer bitplanes. Admittedly, the DEC sixel graphics format wasn't the most efficient, but you at least transferred 6 bits of graphic data for each byte, giving it a 75% efficiency. You would have had to wait almost forever to get a picture like in the video over a serial line at 9600 bps, or even 19200. And once again, no faster serial interfaces were available on a Unibus machine. (Nor did any terminals appear to go that much faster either.) Just make a small calculation. Let's assume a resolution of 640x480, with just 8 bits per pixel. That would mean approximately 300Kbyte of data to transfer. At 19200 bps, that would take 160 seconds to draw one picture. (Assuming all bits were actual data, and no overhead.) Almost 3 minutes... This is easy math, if people just try it. :-) And I dare say, that picture have higher resolution, and more depth than my simple calculation above used. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol