The DSP chips on the MIX card do not all have access to the same amount of RAM.-3 chips have SRAM (Static Random Access Memory). Extremely fast but limited in size. Good for reverbs and short delays (this chip is required for plug-ins such as MegaVerb and Lexiverb).-2 chips have DRAM (Dynamic Random Access Memory). Slow but large in size. Good for long delayeffects.-1 chip has no external RAM. If "compatible" chips are available, this error could be from having peripherals declared on cards other than the first card. The 1.7 version of the Mixer Plug-In does not handle DSP allocation properly in this case. Remove the peripherals (in the Playback Engine dialog) or update to the 1.7.1 (or later) version of the Mixer Plug-In.The DSP's on the MIX cards have many times more internal memory than a 56002 (i.e. chips used on the DSP Farms), so there is enough to do many processes including EQ, dynamics, and mixing.This begs the question... why not build a card with all SRAM chips instead of SRAM, DRAM and no RAM together? The original DSP Farms all had SRAM. This was wasteful when it came to doing long delays liken Procrastinator (1 per DSP limited by RAM) and EQs (which didn't use very much SRAM). An analysis of RAM usage showed that we could best use available board real estate and power by giving different flavors of DSP. This allows more instances per chip, as well as longer delays. The tradeoffis that you can run out of "compatible" chips while there are still DSPs available.This can be caused by the fact that a "compatible" DSP chip is not available. For example, there are 3 MegaReverb compatible DSP chips on a MIX card. These same chips are required by the PlaybackEngine. If you are running the 32 voice engine, then 2 chips are available for MegaReverb (64 voice engine takes 2 chips).You don't use any less DSP when using a Y-cable. However, the DSP is consolidated to one chip since your I/O's are on the same card.if intereseted, try the following:-Assign an interface to each card and you'll probably see a few percentage points of a chip on each card being used for mixer (even if there are no tracks).-Assign 2 interfaces to the same card via the Y cable and you'll see that the first card's DSP is carrying the points that both chips did before.