Concurrent DOS 68K and FlexOS 68K Efforts being part of a cooperation with Motorola since 1984 led to the development of Concurrent DOS 68K in Austin, Texas, as a successor to CP/M-68K written in C. One of its main architects was Francis "Frank" R. Holsworth (using siglum FRH). Concurrent DOS 68K 1.0 became available for OEM evaluation in early 1985. The effort received considerable funding worth several million dollars from Motorola and was designed for their 68000/68010 processors. Like the earlier GEMDOS system for 68000 processors it initially ran on the Motorola VME/10 development system. Concurrent DOS 68K 1.20/1.21 was available in April 1986, offered for about to OEMs. This system evolved into FlexOS 68K in late 1986. Known versions include: Concurrent DOS 68K 1.0 (1985) Concurrent DOS 68K 1.1 Concurrent DOS 68K 1.20 (April 1986, 1986-05-27) Concurrent DOS 68K 1.21 (1986) Concurrent DOS 286 and FlexOS 286 In parallel to the Concurrent DOS 68K effort, Digital Research also previewed Concurrent DOS 286 in cooperation with Intel in January 1985. This was based on MP/M-286 and Concurrent CP/M-286, on which Digital Research had worked on since 1982. Concurrent DOS 286 was a complete rewrite in the C language based on a new system architecture with dynamically loadable device drivers instead of a static BIOS or XIOS. One of its main architects was Francis "Frank" R. Holsworth. The operating system would function strictly in 80286 native mode, allowing protected mode multi-user, multitasking operation while running 8086 emulation. While this worked on the B-1 step of prototype chip samples, Digital Research, with evaluation copies of their operating system already shipping in April, discovered problems with the emulation on the production level C-1 step of the processor in May, which would not allow Concurrent DOS 286 to run 8086 software in protected mode. The release of Concurrent DOS 286 had been scheduled for late May, but was delayed until Intel could develop a new version of the chip. In August, after extensive testing E-1 step samples of the 80286, Digital Research said that Intel had corrected all documented 286 errata, but that there were still undocumented chip performance problems with the prerelease version of Concurrent DOS 286 running on the E-1 step. Intel said that the approach Digital Research wished to take in emulating 8086 software in protected mode differed from the original specifications; nevertheless they incorporated into the E-2 step minor changes