(42S) Programmable Speed-Up in User Code

[Joe Horn]

[The following was posted by Chris Bunsen (d. 31 January 2013) on the comp.sys.handhelds newsgroup on 13 September 1991. It appears here as a kind of tribute to his memory. -jkh-]

My my my.... So nice to hear about happy HP-42 owners. The HP-42 was a true labor of love,
(arent they all?) ..
In that light, here's a little jewel that demonstrates a programmable speed-up in
USER code. I will not/can not/please dont ask me/ explain how come it works, but
it was a lot of fun. By the way, the little bugger has more matrix functions and
abilities than ANY OTHER HP handheld.

1  LBL TT        test
2  BEEP
3  XEQ TURBO
4  BEEP
5  TONE 9
6  RTN

7  LBL TURBO
8  "////"        Four Divide keys
9  111           Rate + 16 * Cont[0:3]  Rate = 15; Cont = 16h
10 XTOA
11 160           Dtst + 16 * Dcont      Dtst = 0; Dcont = 0Ah
12 XTOA
12.5 _"////"     (Untested)--finish filling out ALPHA number with 0s
13 20360         Magic constant to recall Alpha reg as a real
14 8124          Magic constant to store a Complex number over Ctl regs
15 RCL REGS      save REGS
16 CLV REGS      Create bug which allows peek/poke
17 SF 25
18 CLsigma       Now REGS doesn't and does exist!
19 RCL IND ST Z  Recall Alpha data as number
20 1,000,077     Will store complex--must keep timers going
21 RECT
22 COMPLEX
23 STO IND ST Z  Store magic numbers into HDWR registers
24 X<>Y          get REGS back
25 STO REGS
26 END

After running, CPU will run faster. ON key for any reason will restore
slower rate. Batteries don't last long under this regime, and die sooner--
in fact operation is not guaranteed at all.

I had to fix the bug that made this possible; I think the REV Bs and REV C are
"FIXED", but all REV As Ive tried will respond well....

Keep on enjoying our products,
Thank you thank you thank you,
Chris "RPN LIVES" Bunsen
HP -Calc Lab
Corvallis, OR