y2k stuff

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Tue Jan 12 09:02:23 1999

> > Nop - or better partly correct - it is true that not every punch
> > combination was legel (that would be 4096 possible) but at least
> > there was a legal combination for any possible 8-Bit combination.
> > Otherways I would have been impossible to boot from a punch card
> > reader !

> Since when do all machines have 8-bit instructions, and since when do all
> machines represent one instruction as one column on a card, and since
> when do all machines have binary instructions?

Did I say this ? I just mentioned that there is a legal (within
IBM style 12 row cards) method to code all opssible 256 combinations
for 8 bit bytes - starting from 12,0,9,8,1 for x'00' up to 12,11,
0,9,8,7 for x'FF'.

I see no way why such a thing is conected to an 8 bit instruction -
it's only the way to encode a byte on one columne, which gives
80 bytes on a card - enough for the first step of a boot loader

> There is no requirement for 256 legal punchings in a column AFAIK.

Just to enter raw binary data from punch cards, and of course
to boot a machine - my main experiance about that comes from
the /370 world, or more exactly from SIEMENS /370 compatible
systems. I still love the simple but _extremly_ variable
structure of almost everything within this systems. You just
entered a valid device address via two turning wheels and
hit the load button - no matter if it was a tape, a disk, a
card reader, a magnetic card reader, a punch tape reader or
what ever (later on even FD drives), the machine starts the
IPL from this device - just reads the first available block
and execute it - simple and powerfull - no boot manager, no
nothing, just any device - you could run the computer just
with card reader and card puncher (if you wanted to have an
output :).

> As an aside, the Philips P850 series have machine-code bootstrap tapes
> that only use printable characters. A single (16 bit binary) machine word
> is stored as 4 characters on the paper tape. The requirements are :
> 1) There must be at least one hole punched per character, apart from the
> leader which is all nuls
> 2) the lower 4 bits of the character are the binary encoding of that nybble.

Talking about paper tapes ?

> That's all. I normally use the characters _at_ to O when I write tapes.
> Philips tapes use 0-9 and J-O I think.

> This machine, therefore will boot from a tape containing only a subset of
> all possible punchings. And I can well believe some card-based machines
> would do the same.

At least /360, /370ish machines want binaty data from
boot devices.

> > > Anyway, a 'byte', or more particularly a character, is not necessarily 8
> > > bits. It may be _now_, but it wasn't then.

> > I love your comments (and I guess you had also some contact with
> > these 9 Bit Byte Bull Mini computers :)

> I've come across enough machines that use 6-bit characters internally....

6 Bit ? thats new - I never have seen a 6 Bit byte computer - I
know 6 Bit only from some serial line encodings.


Ich denke, also bin ich, also gut
Received on Tue Jan 12 1999 - 09:02:23 GMT

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