Post B604wS2RMcDImGDmds by domi@donotsta.re
 (DIR) More posts by domi@donotsta.re
 (DIR) Post #B6020MQrqhQsgcosGu by nina_kali_nina@tech.lgbt
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       Retrocomputing electronics fellows, a question for you.Let's say there's a very slow computer (perhaps 10k ops) that doesn't have an IRQ controller, only memory-mapped IO. How would you retrofit a floppy and/or floppy controller to it, ideally without using an even faster CPU? I guess a handful of 74xx and buffers might be sufficient to operate WD37C65C in non-DMA mode with a massive performance hit, but if I get 300 bits per second from my floppy, is it even worth to have it 🤔
       
 (DIR) Post #B6020MfkxLLHQnmlTk by domi@donotsta.re
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       @nina_kali_nina AFAIR loading from tape on old Atari systems went slower than 300 baud without a fast loader, and the limitation very much was the CPU (however I can’t imagine low quality tapes helped).i wonder how many 74 chips you’d need to hack up a circuit that, once triggered, would start filling one of the DRAM chips with data. a clock (obv), an 8-bit counter, some overflow latches to extend that counter, and then some chips to control bus mastering?
       
 (DIR) Post #B604tsy0mtCDQTvVAG by grapeshot@mastodon.social
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       @domi @nina_kali_nina Does this need to be compatible with PC disk formats? The Apple II floppy controller was made with a PROM and shift register that acted as a state machine and worked without interrupts (but all disk code was cycle timed and the GCR decoding had to happen after reading a track). It wouldn't be too hard to extend this with a small RAM to use as a FIFO to hold a sector worth of data and read it out at whatever speed the processor can handle. https://www.metafilter.com/114962/jmp-TRIGSPIKES#4301468
       
 (DIR) Post #B604viLJG7yV3ShCfQ by nina_kali_nina@tech.lgbt
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       @grapeshot @domi good point. No, it doesn't have to be compatible with PC, it's a much much smaller system
       
 (DIR) Post #B604wS2RMcDImGDmds by domi@donotsta.re
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       @grapeshot @nina_kali_nina ah yes, Woz’s world-famous floppy controller :3