The early computers that used the system processor and memory for display were most definitely limited by the processor's address bus, but most anything since '83 used video cards with their own video processors and video memory. Of course, the computer still needed to maintain the data that the screen was to hold and early PCs were limited to a very small video buffer (A limit defined by IBM; Not Bill), this didn't prevent enterprising engineers from developing high resolution display cards and displays exceeding the 64K limit by using paged buffers on the card itself. I had a CAD/CAM system in '84 that used multi-color vector graphics on a very high resolution display on a PC running DOS.

What gave the Mac the advantage for multiple displays was in fact Quickdraw. From the very beginning, Quickdraw defined the screen as an X:Y map from -32768 to 32767 defining the upper left corner of the visible screen at 0:0. Adding displays simply required that at least one point of the new displays edge was adjacent to an edge point of the previous. That and no fixed location for the screen buffer. Color was always a feature in Quickdraw but wasn't implemented on the display until the Mac II.

Yes, they were limited in their speed by the processor's address bus. They were not limited in their screen resolution, though. Screen resolution is not dependent on how many bits a computer's operating system, or processor, or memory uses. These are unrelated variables.

Trevor

Vector graphics require a lot less system RAM than even a black and white image.

Again, I'm not saying it wouldn't have been possible to do, it's just that getting the software that works with the card, the application, and DOS to all squeeze a portion of themselves into the same 64 KB to work together while dealing with images was already difficult, and as time went on and applications got larger, it got harder. Trying to do it and manage more than one monitor would have made things even worse.

My memories of the 80s and computers all include bumping into memory limits. Even my IIci, which I bought with 8MB of RAM, needed more. ;)

As I said, with video cards, the 64KB limit could easily overcome. The primary problem at the time was clock speed. A larger display required a lot more resources/clock cycles. Vector graphics overcame the speed issue for a highly complex design.

The IIci (I had one too!) was the first color Mac with built-in video. It used the 32bit processor and system memory for the built-in display. I very quickly learned that a video card sped everything up.

Or let you add a second monitor! With 8MB of RAM, the speed difference didn't seem to be as great as people claimed at the time, but I never bothered to measure.

I remember being annoyed by that integrated video, just like some current MacBook owners are. There was less free RAM than on my old IIcx. I forgot if I got the boss to upgrade the RAM. One day we went over to this guy's desk because he had like FIVE megabytes of RAM in his Mac and was running all these programs at the same time. :eek:

If this web site had been around in those days, someone would have posted the tip that if you want to speed up screen redraw on one of those Macs, you put the monitor into 1-bit (Black and White) display mode.