Concurrent CPM-86 3.x
Concurrent CPM-86 is a multitasking version of CP/M that evolved from Digital Researches' earlier multitasking MP/M product. A seperate add-on was available for 3.1 that added DOS compatiblity. This was integrated in to the product and it was renamed to Concurrent DOS.
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https://vetusabandonware.com/download/CPM-86 Plus 3.0/?id=18735
digital-research-cp-m-plus-v-3.0-1-of-2-original-disk.zip 2.4 MB 0xE05FEAEA