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The original IBM PC used a timer from the 8254 PIT and a channel from the 8237 DMAC in order to refresh RAM with dummy reads (and I think used NMI to signal parity errors.) I'd like to know when PC's started having dedicated memory controllers.

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  • It is not the only task of a 'DRAM controller' to do DRAM memory regeneration. The more important part is to properly time DRAM cycles, generate needed control signals and properly mux row/column addresses from the cpu-presented one. Therefore, the DRAM controller existed from the very beginning (and in every machine using DRAM, not only pc), the only difference was which type of refresh it had.
    – lvd
    Commented Nov 11, 2021 at 5:56
  • @lvd Of course it does. The very grandfather of DRAM controllers, Intel's 8203, already offered independent refresh.
    – Raffzahn
    Commented Nov 11, 2021 at 6:11
  • Now, @antony, for the question, it might quite depend on your value or 'PC-compatible', as having a PC not doing refresh via TIMER/DMA is already breaking compatibility. Not sure if there's a straight answer. Having saidthat, there are several kinda to mostly compatible as early as 1981, using dedicated DRAM controllers.
    – Raffzahn
    Commented Nov 11, 2021 at 6:15
  • historyofinformation.com/detail.php?entryid=3847 Commented Nov 12, 2021 at 17:36
  • Actually IBM engineers removed a dedicated dram controller (8203) when they transitioned from the Datamaster to the PC. I imagine they did so to lower costs.
    – Borg Drone
    Commented Apr 17 at 10:47

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