[VBCurtis]

For those curious, but not curious enough to git:

Poly select used some different parameters, notably incr of 110880 (similar to tests Gimarel has run with msieve) and admax (that is, c6 max) of 2e12.
CADO-specific params: P 20 million, nq 1296. I bet they'd have better-yet performance with nq of 7776 and admax around 3e11, for the same search time.
sizeopt-effort was set to 20; I've not seen this set on any previous params file.

sieve params:
factor base bounds of 1.8e9 and 2.1e9.
LP bounds of 36/37, mfb 72 and 111 (exactly 2x and 3x LP, so 3LP on one side)
lambda values specified at 2.0 and 3.0, respectively
Q from 800 million up.
CADO-specific: ncurves0 of *one hundred*. Typical previously was 25 or so.
ncurves1 of 35, typical previous was 15 or so.
tasks.A = 32; this is a new setting not in my ~Sep'19 git version of CADO. This "A" setting, combined with much higher ncurves, appears to be where the new speed is found.
Matrix: target density 200 (170 was prior standard). This number is about 50 higher than msieve's version of this setting, so this corresponds to target density of ~150. Not that crazy for a C240.

I checked the params.c90 file, which is where the CADO team explains the meaning of each setting. No mention of "A". However, there is a new setting:
tasks.sieve.adjust_strategy = 0 # this may be 0, 1, 2. 0 is default. They note that 1 or 2 may require more work than 0, but give more relations.
I checked a handful of other params files in today's git clone, no other use of "A".

EDIT: Aha! tasks.I is not set in the new c240 file; I is the equivalent of siever size (e.g. I=16). tasks.A is set instead. I imagine these are related.