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Comment by rwmj | Hacker News Reader

The concept is old as the hills, if you include static RAM. It was a common way for early digital synthesizers (early 80s) to store patches in battery backed SRAM. Even on removable cards.

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My first encounter with the concept was in 1982 during the summer working at an electronics company. We used the then new 64K DRAMs in production so there was a ready supply of devices vendors had given us for evaluation. I built a 128KB memory board with bank selection logic then wrote a driver for the Flex OS (6809) to make that memory appear like a disk. Also built a similar board with (probably, long time ago..) 27128 eproms that worked as a "ROM-Disk". I doubt I invented the ram disk. I'd probably heard of the idea somewhere, but I hadn't actually seen an implementation before the one I made.

The next year I switched to a larger company for summer work (defense contractor) and there wrote a driver for CP/M that talked to a "server" I wrote running on their VAX (via 19.2K serial). It made a large file on the VAX look like a disk to CP/M. We used this arrangement for backup -- copy all the files from the physical hard drive to the remote drive. Again I don't believe I'd seen this done before but it was a fairly obvious extension of the previous ram disk idea.

Unfortunately it turned out the group I worked for got billed by the computer dept for CPU time and I/O on the VAX and my network attached storage scheme ran up a huge bill so had to be abandoned.

> I built a 128KB memory board with bank selection logic then wrote a driver for the Flex OS (6809) to make that memory appear like a disk.

Oy! I could have written exactly that. What a coincidence :-) I also wouldn't claim invention. Maybe I heard of it, but I'd say the idea is pretty obvious. We made it possible for Flex to run to programs simultaneously and also do print spooling. (That's when I bought an HP 16C. Great help. Still have it.)

If you like FlexOS you'll like this Youtube channel: https://www.youtube.com/user/deramp5113/videos

As for me it's a bit before my time. I started out writing device drivers for Microware OS-9 on 68k.

Also some early general-purpose microcomputer products in early '80s:

http://s100computers.com/Hardware%20Folder/SemiDisk/History/...

http://s100computers.com/Hardware%20Folder/Electralogics/His...

The original GameBoy cartridges often used battery backed SRAM for savegames.

I don't personally, because battery backed SRAM is a poor man's eeprom.

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