AVR-Chat

I'm locking at building a design which would use an ATtiny25, and a 
couple of transistors on a tiny PCB.

The chip is really cheap, but I don't want to spend double that on 
getting it programmed and tested.

Naturally these would be built in a panel, maybe even 256-off on a 
single PCB.

If I want to I can score one side of the PCB, and allow connections 
across and between the units while the panel is still whole.

It may be a real help if I can test all 256 units on the big panel 
before breaking them up for installation.

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What are my options for programming up these 256 chips?

Can I buy them preprogrammed with either my own code, or a bootstrap 
loader?

Can I program many in parallel using a common sequence?

Is it possible for an ATtiny to load it's own code and program itself? 
( I might happily go up to an ATtiny45 if by doing so I could automate 
the programming )

I had a mad idea of trying to organise them all into a bucket-brigade, 
so each one programmed the one on it's left :-)