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Inexpensive personal computers weren’t shipped with EPROMs, they were shipped with mask programmable ROMs. EPROMs were used in development but they were nowhere

• adrian_b 2y ago
  Mask programmable ROM could be used only by the companies whose production of computers had grown enough to make them worthwhile. Moreover, in the beginning Intel was also the main producer of mask-programmable ROMs, which were launched at the same time with the corresponding EPROM, with the 23xx mask-programmable ROMs corresponding to the 27xx EPROMs. All these part numbers belonged to a system used by Intel, where the first digit was "1" for PMOS, "2" for NMOS and "3" for bipolar, with the second digit being the kind of IC, e.g. 21xx for RAM, 23xx for mask-programmable ROM, 27xx for UV-EPROMs and 28xx for electrically-erasable PROMs. Other manufacturers have started the production of memories after a delay of a few years and most of them have made memories compatible with those introduced by Intel and they have kept the 23xx and 27xx Intel part numbers.