Well, I have never ever upgraded my PSP firmware, since I bought it back in 2005. It's been gathering dust as of late and I think it's time that I brought it to light. One of the reasons why I never upgraded to any custom firmware was because I never felt I had a need to because homebrew and emulation was more than possible on a 1.5 PSP. However, I have found that the amount of features available in the custom firmware are so great, that I must indulge myself before the PSP's time of infamy is over.

So could someone help me out for starters? I'm sure there have been many threads like this before, but I want to make sure I upgrade to the best and latest custom firmware possible. Last but not least, how safe and trusted are these custom firmwares? That would probably be my only concern.

Thanks.

I would say CFW 3.80 M33-5 should be fine. I upgraded to 3.90M33-3 and some games somehow stop working for me due to the ISO file might not be ripped properly. I have to redownload full version of the ISO to be able to run it smoothly. Not sure if anyone else have the same problem as me?

1) Install 3.52 M33

2) Update to 3.52 M33-4

3) Update to 3.90 M33


Just do those three things- follow the readme included with each (a monkey could do it), and you can't go wrong. All are 100% stable, reliable and now safeguards are even built into the upgrading process. So yeh, keep the AC power plugged in the whole time and you're set. 100% safe. BK's seal of approval and all.

Since you're already at 1.50, it's gonna be easy. The hard part usually comes with downgrading to 1.50 in the first place.

in before brick+save

I just purchased a Pandora battery bundled with a mem stick that had cfw 3.90 m33-3 on it. No problems at all with ISOs or anything else as described above. Works so easily it's ridiculous. You are fortunate in that you have an original 1.5. I had bough a slim with a very recent firmware and wanted an easy way to get CFW on it.
Anyway, I've noticed that tons of stuff out there for CFW was made to run on 3.71, so I would suggest that if you didn't upgrade to the latest firmware, I'd definitely go with that one. Lots of eboots and homebrew are built around that one. And if you decide to put a custom XMB on your PSP, there are way more built for 3.71 than 3.90, although most of the better ones have been updated to 3.90 also.
Personally, I'd go ahead and go with 3.90, as there are apps out there that would allow you to boot 3.71 if you chose (Popsloader, etc). Then you could have a 3.90 PSP with the option to boot an older firmware with ease. As is, I've only had to enable 3.71 loading to get several PSX eboots to work. I run 3.90 but load, say, Final Fantasy vii eboot with 3.71 in the options of popsloader.
Hope this all made sense. I just woke up so it prob doesnt haha.

Umm... no.

What are you smoking?

Well I just read it all gain and yes, in does, in fact, make sense. So what do you not understand?
Boils down to this, my child:
*Running 3.90 is no problem at all. Not even ISOs, as another member mentioned.
*Running PS1 games under 3.90 may have compatibility issues, since many "out there" are built to run under 3.71. If you use Popsloader, you can run the PS1 game using 3.71, even if you in fact have a 3.90 CFW.
*Custom XMBs (Sony's Cross Media Bar / navigation system) are more plentiful to download for 3.71 systems -vs- 3.90 systems. But the better looking / functioning ones have been updated to run on 3.90 as well.
Yeah, still makes sense to me. Perhaps you didn't catch some of the terminology? I'm not smoking anything so what doesn't make sense to you?