At the time of Doom's production, id Software was using a NeXTcube for its graphic engine development, so the NEXTSTEP version of Doom actually existed before the MS-DOS version. The application is sluggish on anything other than an 040-based NeXTstation/NeXTcube (the more memory the better), and it is missing sound that was added to the PC release. With NeXTSTEP on the most recent i486 hardware, it runs smoothly under all conditions up to screen sizes of 400%. The released version is labeled v1.2, with programming credited to John Carmack, John Romero, and Dave Taylor.