[sdiy] EPROM conversion question

[klosmon]

At 05:50 AM 3/22/2006, Roy J. Tellason wrote:

>What I'd do in a situation like that is put *two* copies of the code into the
>2716,  so no matter which way things were addressed it'd still get it...

I just tried that -- get the same result.

Thanks to all the folks who responded;  based on those responses, I'm 
guessing I didn't explain the problem well enough.

Basically, I've tried this technique with several ROMs, all of which work 
well using versions 6.0, 6.1, 6.1c, etc transferred from a 2708 to a 
2716.  I erase those SAME chips & load them with 7.0 (which was working in 
a 2708), and it doesn't work;  I then erase the chips again, reload them 
with an earlier version, and they work.  I rewire the synth for 2708 chips, 
reload the 7.0 into them, and it works.

The wiring of the chip sockets is obviously good (for 2716, pins 18, 19 & 
20 are grounded, pin 21 is high), since the 2716 chips function correctly 
when loaded with earlier firmware versions.  The ONLY difference is loading 
version 7.0, which, inexplicably, will work in a 2708 chip, but not in a 2716.

To recap:  the chips are all known to be good, the synths I've tried this 
in are all known to be good, the firmware versions are all known to be 
good;  there's just this one instance where it won't work.

I'm seriously;  it's blowing what's left of my mind.

~GMM