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<P>Actually, there are "simple" (cough) equations for calculating *minimum* EPROM storage times. It is based on the temperature, the gate oxide thickness, the initial MOSFET channel capacitance, the doping level and a few more factors. 20yrs is "standard" and probably 25yrs typical. But a LOT of synths that use EPROMs are approaching 25yrs (even the DX-7!).</P>
<P>As far as I know, the smallest new EPROM is a 27C256 (ST makes them). </P>
<P>Not to be alarmist, but it's not too unreasonable to assume 75% of all analog poly synths AND drum machines will be unable to operate over the next 8 years or so.</P>
<P>If the EPROMs don't cause a failure, then the capacitors probably will :)</P>
<P>Paul S.</P>
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<B>On Wed Mar 28 11:27 , Robin Whittle <RW@FIRSTPR.COM.AU>sent:<BR>
<BR>
</P></B>
<BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #f5f5f5 2px solid; MARGIN-RIGHT: 0px">The Jupiter 8 has a Z80 CPU and three or four separate 2716 EPROMs.<BR>
Address lines 2 and 3 are swapped over on the PCB, so it is best to read<BR>
the chip with those pins swapped if you want to see the data as the CPU<BR>
does. However, for copying the chips, just use an ordinary EPROM<BR>
programmer.<BR>
<BR>
How EPROMs or Flash memory chips hold the charge in their little silicon<BR>
islands is something of a wonder, but there is no fixed lifetime for the<BR>
charge draining away or the chip failing in other ways. If they are<BR>
still holding data in a hundred years, or a thousand, it would not be<BR>
entirely surprising. It is a good idea to keep copies of the chips, or<BR>
make sure someone has a copy. In my experience the data rarely, if<BR>
ever, fades away.<BR>
<BR>
I have a big old Benson plotter, the size of a piano - like this one:<BR>
<BR>
<A href="parse.pl?redirect=http%3A%2F%2Fwww.chilton-computing.org.uk%2Fgallery%2Fral82%2Fmed%2Fr82r3197m.jpg" target=_blank><FONT color=red>http://www.chilton-computing.org.uk/gallery/ral82/med/r82r3197m.jpg</FONT></A><BR>
<BR>
The driver software came in Fortran source code on a reel of 1/2"<BR>
magnetic tape. In the heart of its digital servo system (optical<BR>
encoders and DC motors with 0.001" precision) there is a 1702 EPROM:<BR>
<BR>
<A href="parse.pl?redirect=http%3A%2F%2Fwww.computermuseum.li%2FTestpage%2FChip-Intel1702EPROM.htm" target=_blank><FONT color=red>http://www.computermuseum.li/Testpage/Chip-Intel1702EPROM.htm</FONT></A><BR>
<BR>
I keep telling myself I should read the data from this, a triple supply<BR>
voltage device which ordinary programmers can't read, in case the data<BR>
fades away one day. This was the earliest EPROM, and it was probably<BR>
programmed about 30 years ago.<BR>
<BR>
- Robin<BR>
<BR>
<A href="parse.pl?redirect=http%3A%2F%2Fwww.firstpr.com.au%2Frwi%2Fdfish%2F" target=_blank><FONT color=red>http://www.firstpr.com.au/rwi/dfish/</FONT></A><BR>
<BR>
<BR>
keith sterling wrote:<BR>
<BR>
<FONT color=red>> I had a terrific conversation with Paul Schrieber of MOTM the other </FONT><BR>
<FONT color=red>> day, during which he mentioned that my beloved Jupiter 8 was destined </FONT><BR>
<FONT color=red>> for the landfill soon because it contains CPU embedded EPROMS, and </FONT><BR>
<FONT color=red>> all EPROMS have an implied 20 year (or thereabouts) lifespan. Since </FONT><BR>
<FONT color=red>> the Jupiter's ROM is inside the CPU chip it can't easily be read and </FONT><BR>
<FONT color=red>> reprogrammed in a new chip, like one could do with a discrete 2716 </FONT><BR>
<FONT color=red>> type EPROM. </FONT><BR>
<BR>
<BR>
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