Brian A. Davis wrote:

>I just saw a Helix Labs 128K bubble memory card for sale. I know the
>bubble memory systems failed to become popular due to being slow and
>power hungry, but I was interested in buying it more out of curiosity.

Moore's "Law" didn't work very well with garnet bubble chips, since
the size of the magnetic "bubbles" is inversely proportional to the
magnetic field strength.  As a result, the smaller the bubbles, the
higher the fields.  And while the static axial retention field is supplied
by permanent magnets, the rotating fields in the XY plane that are
required to move the bubbles must also be stronger, and that adds
to the power consumption.

If some better material than garnet could have been found, requiring
lower field levels and with smaller bubbles, then a virtuous technology
cycle might have ensued, but it didn't happen.

The biggest interest in bubble memory came from the military, for
whom its non-volatility, coupled with the ability to completely erase
it in a millisecond, was a nice bonus to its hoped-for density.

>Can anyone with experience using bubble memory technology on the
>Apple II platform pass on a little information? Assuming the card is still
>working, do I need specific software to access and store information
>on the card? Does the card require being in a particular expansion
>slot? The card looks like it has onboard EPROM software.

The Helix Labs card is a 128KB pseudo-disk.  The onboard
firmware supports ProDOS and a patched DOS 3.3.  (The patch
has to do with making DOS happy with its 128KB capacity.)

The firmware is slot-independent.  There was a diagnostic
program for the card that could be used to do the equivalent
of a "low-level format" of the bubble memory, but it is seldom
needed, because of the non-volatility of the memory.  (You
might even find it present on the card!  ;-)

Think of it as a slightly-smaller-than-a-floppy, no-moving-parts
disk.

-michael

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