Can I change that?
Right now I'm using the command-line tool...
I don't know how to change that, but it must be possible somehow.
But today I coincidentally stumbled upon an explanation about what happens to the contents of the EPROM when it ages, unfortunately it's german - it can be found here:
http://robotrontechnik.de/html/forum/thwb/showtopic.php?threadid=11457#107449 .
A brief explanation in english would be: All the information inside the EPROM is basically stored in tiny capacitors which are either charged or not, making a bit appear as one or zero. Since there is always some kind of leakage involved, the capacitors discharge over time - the information gets lost.
By lowering the supply voltage of the chip you're trying to read out, you shift the switching thresholds of the circuitry inside the chip slightly. This shift is then hopefully enough to flip the 'broken' bits back to the original value, at least long enough to read the contents of the chip.
But there is no guarantee that this technique works.
Got the win-software running in wine, the last 16 bytes of the gpib-eprom reads the same down to 3.3 V, another erased chip red FF on 4 V and 00 on 3.3.
I guess you should better read the whole chip and not only a few bytes since you don't know at which address a bit might have been flipped. But to be honest i've no experience with that, i'm just more or less citing what i've read before.