On Jun 1, 13:33, Doug Coward wrote:
> 2. About 1982 I started hearing that it was possible to
> build a camera for your pc by "cooking" an EPROM under
> UV light for an extended period until the memory cells
> were still light sensitive but would no long hold a
> charge. Then by placing a len over the EPROM's window,
> you had a real time low-res video image mapped right into
> memory. Again this is one that quite a few people had
> heard about but no one knew anyone that had ever done it.
I've not heard of an EPROM used this way, but DRAMs certainly have been.
It's possible, with care, to remove the metal lid from some
ceramic-packaged DRAMs and add a lens. The memory cells are light
sensitive; the more light, the faster the charge leaks away, so the scheme
is to write 1's into all locations, pause, then read them back.
Unfortunately, on most DRAMs, the relationship between logical address and
physical location in the array is not simply "add 256 for the next row", so
some decoding is necessary. However, at least one DRAM does have such a
simple mapping, and was sold for the purpose. I'm sure it was described in
one of Steve Ciarcia's Circuit Cellar articles in Byte, around 1982, but I
can't find it amongst my reprints. Anyone?
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Received on Thu Jun 01 2000 - 17:58:09 BST