Flashing refers to using the firmware of a different card with the same (or sometimes similar) core and compatible firmware, effectively making it a higher model card; it can be difficult, and may be irreversible. Sometimes standalone software to modify the firmware files can be found, e.g. NiBiTor (GeForce 6/7 series are well regarded in this aspect), without using firmware for a better model video card. For example, video cards with 3D accelerators (most, ) have two voltage and clock rate settings, one for 2D and one for 3D, but were designed to operate with "three" voltage stages, the third being somewhere between the aforementioned two, serving as a fallback when the card overheats or as a middle-stage when going from 2D to 3D operation mode. Therefore, it could be wise to set this middle-stage prior to "serious" overclocking, specifically because of this fallback ability; the card can drop down to this clock rate, reducing by a few (or sometimes a few dozen, depending on the setting) percent of its efficiency and cool down, without dropping out of 3D mode (and afterwards return to the desired high performance clock and voltage settings).