Many gamers experienced skipping full-motion video or dreaded physical "ticking" noises coming from their PlayStations. The problem appears to have come from poorly placed vents leading to overheating in some environments — the plastic moldings inside the console would warp very slightly and create knock-on effects with the laser assembly. The solution was to ensure the console was sat on a surface which dissipated heat efficiently in a well vented area, or raise the unit up slightly by propping something at its edges. A common fix for already affected consoles was to turn the PlayStation sideways or upside-down (thereby using gravity to cancel the effects of the warped interior) although some gamers smacked the lid of the PlayStation to make a game load or work.
Sony then released a version dubbed "Dual Shock", which included a controller with 2 analog thumbsticks and a built in force-feedback feature.
Another version that was colored blue (as opposed to regular console units that were grey in color) was available to game developers and select press. Later versions of this were colored green - on a technical level, these units were almost identical to the retail units, but had a different CD controller in them that did not require the region code found on all pressed disks, since they were intended to be used with CD-R media for debugging - this also allowed the use of discs from different regions, but this was not officially supported, and different debug stations existed for each region. The two different color cases were not cosmetic - the original blue debug station (DTL-H100x, DTL-H110x) contained "Revision B" silicon, the same as the early retail units (these units had silicon errata that needed software workarounds), the green units (DTL-H120x) had Rev. C hardware. As part of the required tests, you had to test your title on both. Contrary to popular belief, the RAM was the same as the retail units at 2MB. The firmware was nearly identical - the only significant change was that debug printf()s got sent to the serial port if the title didn't open it for communications - this used a DTL-H3050 serial cable (the same as the one used for the Yaroze).
A white version was also produced that had the ability to play VCDs - this was only sold in Asia, since that format never really caught on anywere else. From a developer perspective, the white PSX could be treated exactly like any other NTSC:J PlayStation.