[Beowulf] Re: Interesting

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Fri Oct 29 13:56:15 EDT 2010



Jim Lux
+1(818)354-2075 
> -----Original Message-----
> From: Robert G. Brown [mailto:rgb at phy.duke.edu]
> Sent: Friday, October 29, 2010 10:37 AM
> To: Lux, Jim (337C)
> Cc: Ellis H. Wilson III; beowulf at beowulf.org
> Subject: Re: [Beowulf] Re: Interesting
> 
> On Fri, 29 Oct 2010, Lux, Jim (337C) wrote:
> 
> > Or, how about something like the UNICON aka "terabit memory" (TBM) from
> > Illiac IV days. It's a stable polyester base with a thin film of rhodium
> > that was ablated by a laser making 3 micron holes to write the bits.  $3.5M
> > to store a terabit in 1975.
> 
> Burned RO laser disks should in principle be as stable, if the medium
> used is thick enough.  The problem is that CDs tend to be mass produced
> with very thin media, cheap plastic, and are even susceptible to
> corrosion through the plastic over time.  If one made a CD with tempered
> glass and a moderately thick slice of e.g. stainless steel or
> platinum...
> 
> But then your problem is the reader.  CD readers give way to DVD and are
> still backwards compatible, sort of.  But what about the 2020
> equivalent?  Will there even be one?  Nobody will buy actual CDs any
> more.  Nobody will buy movies on DVDs any more (seriously, I doubt that
> they will).  Will there BE a laser drive that is backwards compatible to
> CD, or will it go the way of reel to reel tapes, 8 track tapes, cassette
> tapes, QIC tapes, floppy drives of all flavors (including high capacity
> drives like the ones I have carefully saved at home in case I ever need
> one), magnetic core memories, large mountable disk packs, exabyte tape
> drives, DA tapes, and so on?  I rather think it will be gone.  It isn't
> even clear if hard disk drives will still be available (not that any
> computer around would be able to interface with the 5 or 10 MB drives of
> my youth anyway).

True.. but at least for something like the UNICON, the actual media is in a form that would be fairly easy to fabricate a reader from scratch.  The "dot pitch" was, I think 5-10 microns, and the piece of plastic was about 2 feet long and 4 inches wide.  You can "see" the dots in a microscope, so you could read it by hand, if you had to (although reading a terabit at 1 bit/second would take a mere 31,700 years or so). 
In reality, I think that with a machine shop, I could probably build a reader in a month that would read out at several megabits/second.  You'd need to read some of it by hand to make sure your high speed reader was working.

However, the format has the virtue of being simple and durable.  And the reader is readily reconstructable... one of the problems with newer higher density formats is that it might rely on some exotic technology to read it (this is why I think holographic storage might be tricky, it depends on a lot of other stuff).  

One could probably fabricate a CD ROM reader in about the same 1 month time frame.  The format is pretty simple, and reading the disk isn't an optical challenge.




> 
> This is the problem with electronics.  You have to have BOTH long time
> scale stability AND an interface for the ages.  And the latter is highly
> incompatible with e.g. Moore's Law -- not even the humble serial port
> has made it through thirty years unscathed.  Is the Universal Serial Bus
> really Universal?  I doubt it.  And yet, that is likely to be the only
> interface available AT ALL (except for perhaps some sort of wireless
> network that isn't even VISIBLE to old peripherals) on the vast bulk of
> the machines sold in a mere five years.


I think that 10/100baseT Ethernet might be a longer term bet than USB. But your point is well taken. Firewire/1394 is essentially dead, except in some niche markets.

> Now, however, this general purpose desktop is all but dead, supplanted
> by laptops that are just as powerful, but that lack the expandability
> and repurposeability

I think the lack of expandability is actually a benefit.  It forces people to use abstracted interfaces. Yes USB and Ethernet will go away, but they're a lot more durable and flexible (particularly Ethernet) than ISA,EISA,PCI, PCIx, etc.

This is a curse to us in the space business, where we have 10-20 year lifetimes for equipment, if not longer.  You want to maintain a testbed in the lab, and you have to have decades old computers "under glass" to support some custom peripheral that has a, for example, ISA bus interface, and provides a test interface to the spacecraft hardware.  At least if you have provided an Ethernet interface, I can get a new computer that has an Ethernet, and rewrite whatever software is needed to talk to the device (assuming you documented the interface, and I can find the documentation in all those boxes in records storage<grin>)


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