Years ago I soldered a physical mod chip into my original PS2, it had like 18 or 20 wires or something insane . Took me a solid week of a few hours after work each day, not to mention the pretty involved disassembly and reassembly Crazy !
Roughly like this I guess https://quade.co/ps2-modchip-guide/modbo/v12/
I used the hacked disk and did the cover mod that let's you open the drive without opening it.
Way simpler.
I did that at first but quickly grew annoyed with it. The modchip took me a few hours to install but it was a huge improvement to usability
There's a memory card exploit that lets you load games from ISOs, either from a hard drive or the network card via SMB share. No patching or burning required. Does not work for PS1 titles however.
Also from USB, unfortunately it's only USB 1.1 so titles with FMV sequence tend to stutter, so for slim models the network SMB share it's preferred...
About PS1 titles, there is a Sony PS1 emulator for PS2 called POPS that you can use with OPL but from what I read it has not a wide compatibility and it's not officially distributed by Sony, the other option is to use mechapwn to boot PS1 CDs, but it doesn't work on the early PS2 models according to this: https://github.com/MechaResearch/MechaPwn?tab=readme-ov-file...
There's also the MX4SIO adapter for loading games from a microSD card. It doesn't work with all titles and may have some stutters but I've had pretty good luck with it.
I'm very disappointed in the lack of details about the patcher. Not only does it not provide any insights into how the process works, it also doesn't even include all the relevant information on what the process works on. I assume it works on PS2 DVD games, but does it work on PS2 CD games, or PS1 games?
The details are explained on the Cturt blog mentioned in another post, the original researcher, this one seems a GUI to simplify the process of patching ISO.
About your questions, I would guess transforming PS2 CD title to PS2 DVD first could work.
For PS1 titles, with a different exploit (mechapwn) you could boot them, but read the fine prints as it basically convert a consumer PS2 to a devkit/testkit (DEX?)...
So it seems like the magic here is the "patcher".
I'm looking at the repo [1], but it doesn't give any technical details on the what/how of what it does.
Does anyone know more?
https://cturt.github.io/freedvdboot.html
I think this explains it.
I've been using free mcboot on a memory card with hard disc games for years. I never knew burnt dvds where possible without mod chip
https://cturt.github.io/freedvdboot.html
tldr; out of bounds payload on the dvd player