Which paper tape hole is bit 1?

[Charles]

>Err, that depends on the DEC machine. My PDP11 has bit 0 as the LSB and 
>bit 15 asn the MSB. The PDP8/e on my desk has bit 0 as the MSB and bit 
>11 as the LSB . I don't know of any DEC machine that has bit 1 as the MSB
>
Actually I was referring to the labels within the PC8E schematic
where the punch lines are labeled "HOLE1" through "HOLE8". I agree
that bits should start at 0, and usually do...

As it turns out Hole 8..1 corresponds on a PDP-8 to data bits
4..11 respectively (more significant to least significant). I was
surprised since I expected the hole numbers to increase directly
with the data bit number.

I also found in the archives a copy of the manual DEC-08-NGCC-D
(PDP-8 Family Paper Tape Systems User's Guide) and on page 26/155
(manual page Intro-13) there is a nice diagram of the 8-bit tape. 

So in conclusion the relationships on a PDP-8 are as follows:

Holes:              87654x321
Significance:     MSB.......LSB
Data bus bits:     D4.......D11

The punch is now hooked up (correctly) via my homebrewed driver
card to the PC8E interface, and merrily spews chad all over the
floor at high speed! I can email an Eagle schematic/board layout
for the drive card if anyone wants...

Now looking for a Tally 420 chad bucket :)

-Charles