Make a good MCU 89C51 programmer according to the crooked circuit diagram

Last time I used the 89C51 microcontroller , the K1200 programmer had some problems. I didn't know whether it was the programmer or the microcontroller that had problems, so I made a simple 89C51 programmer myself, mainly because I didn't want to spend any money and used local materials. The circuit diagram was referenced from some information on the Internet.

There are exactly 2 MCU boards, plus an STC MCU.

It's just that there are too many pins and too many flying wires, so soldering is exhausting. Then the microcontroller and VC programming are also exhausting. After a lot of trial and error, I finally succeeded. Burning the microcontroller 89C51 is really troublesome.

Circuit diagram, hand drawn, as simple as possible:

The finished picture makes me dizzy:

The pull-up resistor on the P0 port must be connected, otherwise the data read from the microcontroller will be correct, but it will be strange when burning. The first few random bytes will be correct, but the rest will be 0xFF. No matter how you adjust the program, it will be useless and waste a lot of time. The pull-up resistor is very important during communication.

Later, the K1200 programmer was repaired, so this simple programmer was put back into antique stock.