Hi,
I can't upload code any more after maybe 100 uploads and the existing program on the chip also stop working. It starts showing invalid signature
avrdude: Device signature = 0x00ff00
I am sure my wiring is correct because when I change to another chip, it works. So far, two chips shows this symptom. I suspects that my chips are fake because it's less than 1$.
I use AttinyCore ISP.
Almost certainly, even the good counterfeits are about $2 each.
Guess you got what you paid for.
Still might be worth looking at the schematic of how you have it installed, to check for other issues.
Did you change the voltage 5V to 3.3V maybe? It took me a while to find out that one of my Ebay AT85 looked dead, just to find out that I had it configured for 5V (16MHz). On another occasion I had my programmer on a too fast baudrate for the clockspeed the AT85 was fused for at that moment.
My wiring and voltage is correct. It was uploading fine and start to fail after maybe 100 uploads and when I replace another chip, it is ok. So far 3 chips are gone, I am using the 4th chip. Luckily, I bought nearly 10 pieces.
But how can I deploy it if it's like this.
I actually haven't heard of "counterfeits" dying after so few programming cycles, but I guess these are "desperate times", and who knows what is being sold on the gray market 
I have tried several Atmega and Attiny including Atmega16a, Atmega8, Atmega88, Attiny84, Attiny85. Some are said to be made in Taiwan. All of them failed after a few upload with various error like invalid signatures. While my Arduino Unos (which are also fake because it's just 3$ to 4$ bought two or three years ago) still up and running. All of them bought from China(Aliexpress and Taobao)
Are you planning on updating a "deployed" project 100+ times? Just buy a few real attinys and develop with the real thing; deploy the junk ones after you have your firmware stable.
My concern here is if it's so fragile, how long will it survive on deployment.
We 're not living on the equal world. At my place, beside Chinese product, it's very hard and take more than 1 months to ship product(During covid period) from US/Europe unless I have to spend hefty money on shipping.
Distributors and Hackerspaces (adafruit.com)
Fragile? I think not.
Anyway, the suggestion was to use the "real" for dev/test and the clones for actual product to minimize the need to flash the clone more than once.
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