[sdiy-interim] EPROM Armageddon?

[Robin Whittle]

The Jupiter 8 has a Z80 CPU and three or four separate 2716 EPROMs.
Address lines 2 and 3 are swapped over on the PCB, so it is best to read
the chip with those pins swapped if you want to see the data as the CPU
does.  However, for copying the chips, just use an ordinary EPROM
programmer.

How EPROMs or Flash memory chips hold the charge in their little silicon
islands is something of a wonder, but there is no fixed lifetime for the
charge draining away or the chip failing in other ways.  If they are
still holding data in a hundred years, or a thousand, it would not be
entirely surprising.  It is a good idea to keep copies of the chips, or
make sure someone has a copy.  In my experience the data rarely, if
ever, fades away.

I have a big old Benson plotter, the size of a piano - like this one:

  http://www.chilton-computing.org.uk/gallery/ral82/med/r82r3197m.jpg

The driver software came in Fortran source code on a reel of 1/2"
magnetic tape.  In the heart of its digital servo system (optical
encoders and DC motors with 0.001" precision) there is a 1702 EPROM:

  http://www.computermuseum.li/Testpage/Chip-Intel1702EPROM.htm

I keep telling myself I should read the data from this, a triple supply
voltage device which ordinary programmers can't read, in case the data
fades away one day.  This was the earliest EPROM, and it was probably
programmed about 30 years ago.

   - Robin

  http://www.firstpr.com.au/rwi/dfish/


keith sterling wrote:

> I had a terrific conversation with Paul Schrieber of MOTM the other  
> day, during which he mentioned that my beloved Jupiter 8 was destined  
> for the landfill soon because it contains CPU embedded EPROMS, and  
> all EPROMS have an implied 20 year (or thereabouts) lifespan.  Since  
> the Jupiter's ROM is inside the CPU chip it can't easily be read and  
> reprogrammed in a new chip, like one could do with a discrete 2716  
> type EPROM.  


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