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Comment by numpad0 | Hacker News Reader

What I always wonder about fake SD cards and USB drives is, if they could “run DOOM” - can a microSD card be used as an extremely cost effective, low endurance general purpose computers with single level storage?

Bottom of the barrel microSD is about $2.50, I don’t smoke but a pack of cigarette is over twice as that. So microSD-based devices should be able to be distributed in a similar affordability and scale, with computing resource of perhaps late 80s PC. What could it do, for the good or for fun?

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After a quick search, looking at one such controller [0], it has a 24mhz CPU w/ 16KB RAM and another I came across that has 32mhz CPU and per doom minimum requirements @ 66mhz CPU and 8MB RAM[1], good luck on that. It's been ported to some pretty weak embedded systems before but maybe someone will eventually prove me wrong.

0: https://www.globalspec.com/Industrial-Directory/nand_flash_c...

1: https://www.sysrequirements.com/game/doom

Yes indeed! I've seen a couple hacks along these lines. Bunnie has blogged about it: https://www.bunniestudios.com/blog/?p=3554

> While SD cards are admittedly I/O-limited, some clever hacking of the microcontroller in an SD card could make for a very economical and compact data logging solution for I2C or SPI-based sensors.

Thanks for the link - that was in my mind but didn’t realize I was almost lifting sentences from that page :p

> can a microSD card be used as an extremely cost effective, low endurance general purpose computers with single level storage?

This is exactly what Raspberry Pi's use, so the answer is yes.

I think that the parent post means to use the onboard controller as a CPU and the flash memory as virtual memory (with no ram) and mass storage. I don't think this is actually viable with sd cards but it might work with different memory formats.

Probably not DOOM, but apparently some microSD cards have microcontrollers that can be exploited to run arbitrary code: https://www.bunniestudios.com/blog/?page_id=3592

Despite being solid state, SD cards have horrible random read and write speeds, worse even than HDDs. They're made for storing media from cameras, so it doesn't matter.

Maybe RPis do OK cause they just load the system once, maybe even sequentially. I also keep a card in my MBP. It takes forever to write directories, but it's good enough to store Xcode etc only cause the RAM caches things. Torrenting Ubuntu onto it was unusably slow. I expect it'd be unusable as single-level storage.

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