My HP 10bII+ is much faster than HP 12c!

[Albert Chan]

My guess so many calculators failed this is because we have multiple solutions.
For my posted example, we have 2 (real) solutions for I.

Using HP-12C IRR (with the good guess), it did solve them.

Clear Reg
1000 CF0      ; PV
CHS CFj        ; PMT
29 Nj            ; N-1
49000 CFj     ; FV + last payment

IRR                             → Error 3
3 [i] RCL [g] [R/S]       → 3.651974353
100 [i] RCL [g] [R/S]    → 99.99999525