Yes, Metric Halo were the first. And, when it comes to "sound quality", their units were better than anything else available at a time, ProTools HD including.
Excerpts from main coder's posts to their mailing list in 2001:
Mobile I/O uses the Analog Devices SHARC 21065 DSP. This is a 40 bit
floating point processor which can also do 32 bit fixed point with 80 bit
accumulation. For large MAC (multiply accumulate) loops, like summing in a
large mixer, wide fixed point processing can provide better results, but for
most applications, wide floating point is the way to go. The nice thing
about the SHARC is it gives you the freedom to use the best arithmetic
system for a given processing application.
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The DSP is 40 bit floating point and 32bit fixed with 80 bit accumulation.
Calculations are maintained at high precision internally and dithered to 24
bit for output.
Base 2882 units got you only high resolution mixer, but, if at the time of purchase you opted for +DSP option (second DSP chip, additional $700) you got a bunch of hi-rez plug-ins that ran on the second chip.
Just for the kicks I downgraded one of my 2882+DSP to pre-2d state (OS9 compatible) and this is what I got.
* familiar to all Channel Strip, but in higher resolution
* Compressor
* Limiter
* 6 band EQ
* 12 band EQ
* M/S processor