CASIO FX-730P Personal Computer, Japan, year 1988

[jebem]

Memory test

(edited to add hyperlink to the Tandy service guide)
I found this memory test in one service guide for Tandy PC6 that looks similar to FX-730P and FX-780P CASIO machines (at least the specifications and schematic diagram applies to the FX-730P).

I tried it and it failed with ERROR1 (insufficient memory). Then I realized the program contains a few issues:
- P1 has got an extra line 101 that is never executed in the algorithm but it takes memory that makes impossible to use 904 cycles as defined in P0.
- P1 has a logic error in line 40. It is testing for "equality" when it should be testing for "inequality".

Procedure to test the memory:

1. Start by doing a hard reset so that the remaining memory capacity=7520 (do a MODE 1 to check it).

2. Type in the memory test programs P0 and P1.
Program P0 writes once to RAM memory.
Program P1 reads from RAM memory in a 4 times loop.

3. Execute program P0
Program P0 executes during 40 seconds and in the last instruction it jumps to Program P1 that takes about 140 seconds to execute if no errors are found (4 passes).
After execution, the remaining memory capacity=9.

Program P0
To type in P0, go into WRT mode (MODE 1) and select program area 0 (Shift P0)

Code:


10 CLEAR
20 C=904
25 DEFM C
30 FOR B=1 TO C
40 D(B)=B
50 NEXT B
60 $="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
70 BEEP 1: BEEP 1
80 PRINT "INPUT OK*";
90 GOTO #1

Program P1
To type in P1, select program area 1 (Shift P1)

Code:


  5 A=0
  7 A=A+1
 10 FOR B=1 TO C
 20 IF D(B)<>B THEN 100
 30 NEXT B
 40 IF $<>"ABCDEFGHIJKLMNOPQRSTUVWXYZ" THEN 100
 50 IF A=5 THEN 110
 60 PRINT A;: GOTO 7
100 PRINT "CHECK**NG**;: BEEP 1: BEEP 0: GOTO 111
110 PRINT "CHECK**OK**";: BEEP 1: BEEP 1
111 PRINT "A=";A;: END

Program P0 terminated execution and jumped to program P1:


Program P1 terminated execution with no errors: