ROM to RAM Copier

Copies the 8K ROM into RAM at addresses 8192–16383, for a machine with memory fitted in the 8K–16K area. The first part, lines 10–75, compares every byte from 49152 to 65535 with the ROM, in two passes of 8192 bytes, and stops at the first mismatch; if the upper memory is a mirror of the ROM it prints the final address, 65536. The second part, started with GOTO 80, reads each ROM byte with PEEK and POKEs it into the 8–16K block.

It came from an unlabeled tape. Two recordings, ROM1 and ROM2, are identical. Line 160 saves the program as ROM and line 170 restarts it with RUN after loading.

Program Analysis

Program Structure

• 10–75: verification loop. X starts at 49152 and keeps rising across both passes of the J loop while I runs 0–8191 each time, so the 16K from 49152 up is checked against two copies of the ROM.
• 80–150: copy loop, one byte at a time, with PAUSE 3 after each byte.
• 160–170: SAVE "ROM" and RUN.

Potential Issues

• The PAUSE 3 in the copy loop adds about seven minutes of waiting across 8192 bytes; the program does not say why it is there.
• On a machine with no RAM at 8192–16383, the POKEs have no effect, and the program does not check that the copy worked.

  10 LET X=49152
  20 FOR J=1 TO 2
  30 FOR I=0 TO 8191
  40 IF PEEK X<>PEEK I THEN STOP
  42 LET X=X+1
  50 NEXT I
  60 NEXT J
  70 PRINT X
  75 STOP
  80 LET X=8192
  90 FOR I=0 TO 8191
 100 POKE X,PEEK I
 120 PAUSE 3
 130 LET X=X+1
 140 NEXT I
 150 STOP
 160 SAVE "RO[M]"
 170 RUN