On 3/1/2026 3:47 PM, Van Snyder via cctalk wrote:
On Sun, 2026-03-01 at 15:32 -0600, Steve Lewis wrote:
The IBM 1401 has a "tape load" key. Oddly, the 1410 didn't. One needed
to key "L%U100011R_" into location 1 and set the instruction address to
00001.
As you say, the 1410 did not have a load key. The 7010 did have a
momentary load switch: left for card, right for tape. I might add that
feature to my FPGA 1410 someday. ;)
On the 1410, because a tape in load mode was necessarily in odd parity,
you would use L%B rather than L%U
Usually one used "read to end of core", so the d character would be $
rather than R
For a real 1410, the usual boot process was:
1. Clear storage
- Set the sense/bit switches to a blank character (just the C bit)
- Set the memory regen to +1
- Set the Mode switch the CE
- Press START, and enter the address 00000
- Wait a second, then press computer RESET
2. Display enough memory that you could enter the boot instruction.
This required either display up to a word mark, but with storage clear,
instead one would hit the index key on the selectric console to fudge an
end of line which accomplished the same goal.
- Set the mode switch to DISPLAY
- Enter address 00000 (or sometimes 00001 if a blank was OK in location
0, but usually 0)
- Press START, then after a second or two of bbbbbbb press the index key
on the console selectric to force a new line
- Set the mode switch to ALTER
3. Enter the instruction to boot from tape
- (Mode switch already in ALTER)
- Press START
- Enter: b<WM>L%B000011$<WM>.<WM>. [Diagnostics, PR108, etc.]
Sometimes a different character than b (blank)
- Enter: A<WM>L%B000012$<WM>N [PR-155, normal boot == A in location 0]
(For a card boot, one would enter b<WM>L%1100011$<WM>.<WM>. I don't
recall every doing a card boot on our 1410)
4. Press computer RESET (which happens to set the I Register - the
program counter - to 00001)
5. Press START
