--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/FCDEV3B-751774	Mon Nov 18 05:03:15 2019 +0000
@@ -0,0 +1,29 @@
+We have one experimental FCDEV3B V2 board on which our regular Calypso chip
+([P]D751992AGHH) has been replaced with D751774AGHH, an earlier F-number
+featuring DSP ROM version 3416 rather than the final version 3606 which we
+normally work with.  Both chip versions are Calypso C035 variants (ARM7 running
+at 52 MHz, DSP running at 104 MHz), and both include AMR support - but there
+must have been some issue with DSP version 34 (and maybe version 35 used in
+Calypso+) that compelled TI to produce the newer and final version 36 which we
+are most familiar with.
+
+Our Layer1 code is based on TI's TCS211-20070608 semi-src release (which we have
+reconstructed back to full source), and it officially supports only DSP 36.
+However, our FC Magnetite firmware can also be built for DSP 34 targets (see
+the Calypso-version-override article), in which case we use a monolithic DSP
+patch (no L1_DYN_DSP_DWNLD) extracted from the TSM30 source.  The patch version
+is 4130.
+
+The configure.sh target name for this special modified board is fcdev3b-dsp34
+instead of just fcdev3b, and the two firmware builds are not interchangeable:
+the regular fcdev3b build goes into regular FCDEV3B boards, the special
+fcdev3b-dsp34 build goes into the special FCDEV3B-751774 board.  However, when
+running its respective build this DSP 34 board appears to function just as well
+as our regular DSP 36 targets: standalone RF tests work, DSP-based audio
+services (beeps and Melody E1) work, connecting to a live GSM network worked,
+a few test voice calls worked, all of them connected in AMR mode, voice passed
+successfully in both directions.
+
+Going forward, we shall continue using D751992AGHH chips with DSP ROM version
+3606 as our regular platform, but it is nice to know that the earlier DSP 34
+apparently works too.