Hmm. dump it 5 or 6 times, and note what addresses/bits are unstable. Also, if your programmer supports it, try dropping the VCC voltage from 5v to 4.95 or 4.90v, this often helps with decayed-floating-gate (aka "bit-rotten") eproms, since it affects the voltage threshhold for the '1 vs 0' comparator per-bit. On 5/25/2016 9:00 AM, Jason Perkins via vcf-midatlantic wrote:
Johnathan,
Don't worry, that's the first thing I did. I also found that after a couple reads a few bits had flipped!
On Wed, May 25, 2016 at 7:27 AM, Jonathan Gevaryahu via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Be sure to dump the existing eprom first just to make sure that it is dead. We've lost more firmware revisions than I can count (and yes, even old/obsolete versions need to be preserved) by people just wiping and reburning eproms without checking to see whether the version on it originally was known or not.
On 5/24/2016 11:22 PM, Jason Perkins via vcf-midatlantic wrote:
I'm trying to get a Plus HardCard going again. Like many the ROM has forgotten some of its bits so I want to try installing a freshly flashed one.
What's a good source for 7264s? Is it worth trying to get used ones on eBay? While I'm at it I'd like to track down a 2732 for an Apple ProFile formatting rom.
Thanks,
-- Jonathan Gevaryahu jgevaryahu@gmail.com jgevaryahu@hotmail.com
-- Jonathan Gevaryahu jgevaryahu@gmail.com jgevaryahu@hotmail.com