[monocasa]

The channel I/O format has conditional jumps in the command stream and lets you as the application programmer offload large parts of the filesystem or database directly onto the hard drive controller without main CPU intervention. It's closer to GPU command submissions than what you see out of NVMe/SCSI/ATA. So, for one example, telling the controller to "walk an index tree in this format and retrieve the block that matches this key" is something you can code yourself in the channel I/O command stream as it's own sort of ISA.

[Teknoman117]

From the "roads not taken" perspective, Intel actually made something like a channel IO engine for the 8086/8088 family called the 8089 (https://en.wikipedia.org/wiki/Intel_8089) which supported the 20-bit address space of those systems and proper 8 and 16-bit operations. You could write little programs for it which would communicate with IO devices and respond to interrupts on either a shared or private bus, do some processing, and then move the results to main memory.

IBM in a cost saving move grafted the DMA engine from the 8080 family (the 8237) and made it mostly work by adding a page register to cover the remaining bits and setting one up in an odd way for the 286 to get it to do IO <-> memory transfers for 16-bit devices (but unable to do memory-to-memory transfers).

[trasz]

See eg https://netfpga.org for pretty much exactly this for network. I believe it's more of a research platform than something that's used in production. It's not exactly new either.

[rbanffy]

Not quite, because this is reconfiguring the hardware itself, but similar in intent.

[rbanffy]

As a note, Commodore’s 1541 and 1571 drives ran the filesystem in the drive themselves. The computer only sent file commands to the drive.

[monocasa]

And even a faster 6502 than the CPU! Yeah the true very programmable I/O offload you see in the C64 is very similar conceptually, and would be even closer if it could DMA into main RAM to communicate with the main CPU rather than bitbanging serial.

[rbanffy]

I wonder if one could do some useful computation within the drive itself, like adding columns from or sorting a CSV file.