ATMEGA 1284 boot loader

Hi,
I have a MEGA 1284 built onto a breadboard, after installing Optiboot I ran a blinky test sketch and all was fine. After a change to 3.3v operation and 12 MHz crystal ( was 16 MHz) I loaded a different version of optiboot, ran the blinky again and all was well.

I then tried connection a Wiz820IO module, there was no response. Checked it using a MEGA 328 and the wiznet module was fine. I then though I would go back to the original Optiboot and try that, but now I can't load any version of Optiboot at all.

Error returned is: avrdude protocol error expect 0x14, response 0x50
Using an arduino as ISP
Original Optiboot was from maniacbug
Second version of Optiboot homehack-max

Any help or suggestions would be apreachiated.

Two possible suggestions. First, are you really sure you hacked the bootloader code correctly
for operation at 12 Mhz? That's a non-standard clock value, and all the timing and baudrate
settings will be very different. Might be easier to try 8 Mhz, as that's a standard, and
bootloaders are already available.

Secondly, the 328 and 1284(P) chips run perfectly well with 16 mhz xtal at 3.3V [despite
some dire warnings of imminent chaos and disruption on the horizon]. So, you might "try"
it that way [but always be careful to watch for chaos showing up]. If you look at the
datasheets carefully, and interpolate the graphs, you'll see they show clock = 13.3 Mhz
at 3.3V, so 16 Mhz is "only" 20% overclocking.

Also, note that you cannot burn the bootloader into a 1284 chip using the 1284P setting,
in case you really have a 1284 and not a 1284P chip.

It is an ATMEGA1284P so that should not be an issue.

I downloaded both bootloaders, I am afraid hacking a bootloader is beyond my skill set. The main issue at the moment is that I can no longer get a bootloader to load. Could this be due to an issue with the bootloader that is currently installed, nd is there a way to reset the processor back to default?

The maniacbug optiboot will burn fine into the 1284P, with 16 Mhz xtal.
Look at this tutorial,

Hi, the maniacbug boot loader did load fine, then I changed it to the home hack-max boot loader. Now I can't get any boot loader to load at all.

Are you trying to reburn the bootloader or burn a sketch into the chip?

If you can't reburn the bootloader using the ArduinoISP, then maybe you be a regular
ISP programmer to erase the chip completely, but I don't know anything about that.
??? [you need to find one of the big guns around here, ;-)].

The 1284p (328p) works fine @16MHz and 3V3. Set full swing oscillator to be safe..
Atmel guarantees the parameters in -40..+85 degC region, therefore the official MHz rating for 3V3 is lower..