limit of 800×600 with 16 colors (or 400×600 with 256 colors), as well as other custom modes using unusual combinations of horizontal and vertical pixel counts in either color mode. Software such as Fractint, Xlib and ColoRIX also supported tweaked 256-color modes on standard adaptors using freely-combinable widths of 256, 320, and 360 pixels and heights of 200, 240 and 256 (or 400, 480 and 512) lines, extending still further to 384 or 400 pixel columns and 576 or 600 (or 288, 300). However, 320×240 was the best known and most frequently used, as it offered a standard 40-column resolution and 4:3 aspect ratio with square pixels. "320×240×8" resolution was commonly called Mode X, the name used by Michael Abrash when he presented the resolution in Dr. Dobb's Journal. The highest resolution modes were only used in special, opt-in cases rather than as standard, especially where high line counts were involved. Standard VGA monitors had a fixed line scan (H-scan) rate"multisync" monitors being, at the time, expensive raritiesand so the vertical/frame (V-scan) refresh rate had to be reduced in order to accommodate them, which increased visible flicker and thus eye strain. For example, the highest 800×600 mode, being otherwise based on the matching SVGA resolution (with 628 total lines), reduced the refresh rate from 60 Hz to about 50 Hz (and 832×624, the theoretical maximum resolution achievable with 256kb at 16 colors, would have reduced it to about 48 Hz, barely higher than the rate at which XGA monitors employed a double-frequency interlacing technique to mitigate full-frame flicker). These modes were also outright incompatible with some monitors, producing display problems such as picture detail disappearing into overscan (especially in the horizontal dimension), vertical roll, poor horizontal sync or even a complete lack of picture depending on the exact mode attempted. Due to these potential issues, most VGA tweaks used in commercial products were limited to more standards-compliant, "monitor-safe" combinations, such as 320×240 (square pixels, three video pages, 60 Hz), 320×400 (double resolution, two video pages, 70 Hz), and 360×480 (highest resolution compatible with both standard VGA monitors and cards, one video page, 60 Hz) in 256 colors, or double the horizontal resolution in 16-color mode. Hardware manufacturers Several companies produced VGA compatible graphic board models. ATI: Graphics Solution Plus, Wonder series, Mach series S3 Graphics: S3 911, 911A, 924, 801, 805, 805i, 928, 805p, 928p, S3 Vision series, S3 Trio