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Punch cards (was Preparing the reduced bootstrap tarballs)

From: Timothy Sample
Subject: Punch cards (was Preparing the reduced bootstrap tarballs)
Date: Tue, 20 Nov 2018 10:28:10 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)


Ricardo Wurmus <address@hidden> writes:

> address@hidden writes:
>>> for the lazyer like me, what about a punched card? :-)
>> If someone is willing to figure out how to read a deck of punched cards
>> without software, I'd be interested in learning more.
> Now that’s a project for a free hardware design that I’d happily work
> on :)
> Reading and transmitting of the bitstream can be done in hardware alone
> (shift register, MUX, photoresistors, …), though I’d need to know what
> kind of interface there is on the receiving side.  Just flash memory /
> TTL shift register?

I’ve thought about this a bit.  Would it be possible to go even more
mechanical, and implement the SPI protocol in switches toggled by holes
cut in some kind of insulating tape?  You could have a couple of steel
balls (bearings?) balanced on top of each other, connected to a circuit
using brushes or springs.  Then, you place the tape in between the
bearings.  When there’s a hole in the insulating tape, they make
contact, and when there is no hole, no contact.  Then, you have a row of
holes for the SPI clock, and a row of holes for the SPI data.  All you
would have to do is hook up the right voltage to it, and you could write
to a flash ROM by pulling manually punched tape through it.  (You could
use a crank or motor if the timing needs to be more precise.)

Then, you could take an x200 and setup the bootrom to be whatever you
wanted with no software whatsoever.  If you adjusted stage0 to set up a
“cache-as-RAM” environment (like they do in coreboot), you could do
quite a bit of manoeuvring before having to initialize RAM.  That is,
you could probably set up a tiny Scheme environment and do more hardware
initialization from there.

Obviously all of this would be easier on a simpler computer, but then
presumably you have to move from a simpler computer to a more
complicated computer at some point (depending on your needs).  The nice
thing about booting the x200 as a simple computer is that you can just
expand its boundaries until it is full-featured.

Sorry for derailing a bit, I just wanted to share some idle thoughts.

> --
> Ricardo

-- Tim

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