what is the difference between regular start metal halide lamp and the pulse start variety?

Answer 1

There is a normal lag of several minutes (depending on ballast type and ambient temperature) before a regular MH lamp comes up to full illumination brightness. This can be a real problem in lighting areas where these lamps are used such as parking lots, garages and large commercial and industrial spaces, especially after a power outage. For safety reasons, it's been required by building codes to have small auxillary quartz "restrike" lamps installed inside of some of the fixtures so that they will re-light more quickly and assure that people aren't left in the dark til all of the lights warm up.
The newer pulse start lamps come up to full brightness much more quickly, eliminating the need for "restrike" lamps.