M33 firmwares are custom firmwares developed by Dark AleX. They are based on Sony's firmwares starting from 3.51 and above. Earlier custom firmwares by AleX were known as OE (Open Edition) firmwares and SE firmwares. Except for the different name, M33 firmwares follow the same concept as OE/SE firmwares; i.e. Removing restrictions from Original firmwares, full homebrew support and lots of customization possibilities. M33 firmwares 3.60 and above can be installed on Slim PSPs too.
These are the new features introduced in M33 firmwares:
- Video ISO loader
- The new M33 NoUMD Driver and support for Sony's NP9660 NoUMD Driver
- A revised Recovery Menu with more features added in
- VshMenu, a small in-XMB plugin to change settings normally accessable only in the Recovery Menu.
After Dark_AleX supposedly retired from the PSP scene, he and a few other sceners continued, under the pseudonym of Team M33 developing Custom Firmware with the tag of M33 (rather than OE/SE). On July 14, 2007, the first release rolled out. Almost everything resembled some part of OE including the installer. After 7 updates to the base firmware, bugs were fixed, and more features were added in to expand on the firmware. This remained the basis for most of the future releases.
All of the 3.40 OE features still remain on the M33 Firmwares. However, the only feature that lacks past 3.52 M33 is the autoboot program that allows programs to be run from a coldboot.
ISO play still works, with the ability to the OE, M33, and Sony NP9660 NoUMD Drivers to play backed up games. Compatibility and speeds have been improved in the newer M33 and Sony NP9660 Drivers.
All aspects of recovery mode works across both Phat and Slim PSPs except for the autoboot, and recovery to 1.50 on Slims. PSP Slim & Lite users, however, have the option of utilizing a special USB Charge plugin, allowing the user to charge their PSP via the USB Cable without activating USB Mode.
PSOne games can be played with better compatibility across both the Phat and Slim PSPs. Multi-disc games can also be played as long as they are converted properly using utilities like PopStation MD.
The VshMenu, a new addition to the M33 firmwares, allows users to quickly over/underclock their PSPs, change the ISO loader plugin used for backups, change the XMB USB Device (Memstick, Flash0, Flash1, etc), mount video ISOs, and reset the device.
14 July 2007 Download: 
All of the 3.xx OE features remained, except that it used the 3.51 firmware (which added 3.50 features, for those still on 3.40 OE), which was actually the Illuminati patch.
14 July 2007 Download: 
17 July 2007 Download: 
It added the NO-UMD modes, which added M33's own ISO loader, and Dark_Alex's ISO loader from the OE firmware.
18 July 2007 Download: 
This fixed bugs in the NO-UMD modes that were released the day before. Also, this allowed plugins to be used in homebrew that were in the GAME150 folder.
18 July 2007 Download: 
This update fixed another two bugs with the NO-UMD modes.
19 July 2007 Download: 
This update added in Sony's NP9660 ISO loader that was discovered on firmwares past 3.51.
21 July 2007 Download: 
The last update, 3.51 M33-7 fixed several bugs, and added improvements to different features. M33's ISO loader speeds were improved, brightness issues were fixed throughout the system, (with the 1.50 kernel brightness added) the WLAN fix was implemented in a different way, and an option was added in recovery for those still experiencing WLAN issues. Before any updates were released to the 3.51 M33 firmware, a WLAN fix was added for those experiencing WLAN issues with their system. With the initial release optional, it later was added in the later updates.
25 July 2007 Download: 
This included all the features of 3.51 M33, and it moved up to the 3.52 firmware. The initial release fixed a bug with the Go!Cam, GPS, and the sceKernelLoadExecVSH working properly while in a game. Also, the compatibility of the NO-UMD mode was improved to allow games downloaded from the PSN to be played properly.
30 July 2007 Download: 
This fixed the compatibility issue with PSX games in IRSHELL via usbhostfs and nethostfs. Also, the document.dat from PSX games didn't need the same game ID as the game itself for it to work. In recovery, the "use isofs with UMD inserted" was stripped as it wasn't useful anymore. Speeds of 20 Mhz and 100 Mhz were been added as option for underclocking the system. Also, while USB Mode is activated, the ability to turn off the PSP is disabled completely. (Therefore, the only way would be a hard reset by taking out the battery) The issue of Chinese and Korean fonts crashing the XMB and homebrew was fixed. However, the Korean font has to be added from a 3.52 dump. Also, popsloader was added, and it allowed POPS to be loaded from 3.40, 3.51, and 3.52. However, the necessary files have to be dumped from the firmwares, and moved to the memory stick.
19 August 2007 Download: 
In recovery, 75Mhz and 133Mhz were added as speeds for underclocking. USB to flash2, and flash3 was been added. Under the config, an option to change the device that will be mounted in the XMB under USB Mode was added. This could be changed between Memory Stick, flash0-3, and the UMD Disc. In the XMB menu, a new vshMenu was added. This allowed CPU settings, the ISO loader settings, as well as the XMB USB Mode to be changed on-the-fly. However, due to the fact that it is brought up by pressing the HOME button, other XMB plugins using that key will not work. Therefore, an option to turn off the vshMenu was added in recovery. The final change to the XMB was the ability to mount and play UMD ISO Videos. Games and Videos will appear under GAME. In popsloader, support for 3.30 POPS was added.
21 August 2007 Download: 
This was the last update to 3.52 M33. This fixed the CRC error while flashing in the XMB over USB. Also, the 75 and 133 Mhz speeds were added to the vshMenu since it was forgotten by the team. Support for 3.10 and 3.11 POPS were added in.
The Bricking Issues
A few people had been editing Team M33's custom firmwares to remove credits. With the release of 3.52 M33-4, Team M33 added extra protection which verified the authenticity of the downloaded files. If the verification failed (i.e. Files had been edited/modified in any way), the updater would brick the PSP. Soon after this, members from N00bz, M33 and Team C+D came together to release the Pandora Battery, which was the culmination of years of research.
10 September 2007 Download: 
3.60 M33 was released 5 days after the inital Slim release. Installation was different on a Slim since it lacked support of the 1.50 kernel. However, installation was possible with the use of a modified Pandora Battery install. Instead of installing 1.50, it just flashed the M33 files. Due to this method, it proved effective only on Slims that were on 3.60. If it was on any other firmware, it didn't work. Also, 3.60 was a Slim-only firmware, and wouldn't work on a Phat. If attempted, the system would either brick or the custom firmware would become partial, or corrupted. 3.60 M33 contained all of the features of 3.52 M33, as well as the Slim-only features such as the Cookies theme, TV output, etc.
23 September 2007 Download: 
Within days of the 3.60 release, 3.70 was released for both Phats, and Slims, and 3.71 was a quick fix. As stated before, the Pandora install of 3.60 M33, was useless on 3.71, and therefore, a new method of install had to be created. Using the same Pandora Battery, Dark_Alex developed a method that installed a fresh copy of 3.71 as well as the M33 files, or just 3.71 if the user chose to. For those on 3.52 M33 and Slims already on 3.60 M33, they were able to update normally without the use of Pandora Battery. On 3.71 M33, the vshMenu was remapped to SELECT since the HOME key was in use more since 3.71. On the Slim, the UMD Cache feature was disabled only if the user launched homebrew. This was to allow the memory need for homebrew games which before, wasn't available due to the UMD Cache taking it up. Also, both on the Phat and Slim, booted from the 3.xx ipl instead of the 1.50 ipl.
The installer from 3.71 M33 onwards used a modified version of the Sony installer. Due to this, an IDStorage degeneration check was put on the installer. However, this checked mainly for key 5 on TA-082/086 motherboards, and degeneration on other motherboards may or may not be picked up by the installer. However, there are many different methods of resolving this issue. Also, since 3.71 M33, the installer doesn't install the 1.50 kernel anymore. However, the 1.50 kernel addon was released for Phats, and it installed the 1.50 kernel at the expense of the Location Free Player, and the Korean font. The Location Free Player was still available if the specific files were flashed after the installation. However, with each version of the 1.50 kernel addon, the same files would be deleted before install. Therefore, the files had to be reflashed again.
2 October 2007 Download: 
A bug that corrupted flash0 while writing over USB was fixed. However, another bug came and caused the same problem. On Slims, they were allowed to charge over USB, as long as the option was set in recovery. Charging worked anywhere as long as the PSP was on. The vshMenu was disabled while using the on-screen keyboard. (OSK) This prevented the loss of the SELECT button while using it. Also, vsh plugins were not activated in recovery, because it led to pseudo-bricks.
8 November 2007 Download: 
On the same flash0 corruption bug that was fixed on 3.71 M33-2 was fixed again with this release. With M33's ISO loader, two bugs were fixed. Also, the vshMenu was now displayed properly while using TV-Output on Slims. Also, Popsloader for 3.71 M33 was released, and it did require 3.71 M33-3 and the several files from the different firmwares in order to work.
12 December 2007 Download: 
This allowed multi-disc PSX games to be played. Also, multi-disc games bought from the PSN store would work again. Also, bugfixes with the 3.72 POPS has been fixed.
14 January 2008 Download: 
This update adds a new network update feature which, when enabled, will check for M33 firmware updates. When the feature is disabled through the recovery menu, the network update feature operates as it normally does checking for Sony firmware updates.
14 January 2008 Download: 
Team M33 also released update 2 on the same day which fixes with scePowerGetClockFrequencyInt not being resolved properly. Update 2 also fixes a problem with the way PSX eboot icons are displayed if they are 80x80 pixels. a 1.50 Kernel update was also released.
January 16 2008 Download: 
It fixed a synchronization issue that plugins check code cause in PSN NP9660 original games. Also added were a couple libs to the nids resolver and some internal changes required for the new version of the popsloader which was released on that same day.
January 16 2008 Download: 
Update 4 was released on the same day to address a quick bugfix, galaxy.prx was updated because it was causing a problem with slow memory sticks.
20 January 2008 Download: 
Fixed custom CPU clock not working in games. CPU clock has never (in any SE/OE/M33) been set at all in games that restarted using sceKernelLoadExec to use a subgame or reload themselves, after said restart happened (e.g. Castlevania). Fixed. Added setting to recovery to hide PIC0.PNG and PIC1.PNG in the XMB game menu. By default, this setting is turned off. This feature, when turned on, results in faster browsing speeds in the XMB Game menu. This setting only applies to any kind of apps/games (pbp, iso) that load from MS, but not to UMD's.
8 GB stick support for 3.80 M33 Popsloader
On February 11, 2008, Dark_Alex unofficially released a patch for users of 3.80 M33 Popsloader that allowed them to use 8 GB memory sticks along with the popsloader. However, with this patch, the system will not boot without a memory stick, and supposedly, the unit will also brick without the memory stick inserted.
31 January 2008 Download: 
Uses new FW 3.90 kernel, and March33 NO UMD fixed (yet another bug related with exiting with home, infinite semaphore wait). There were also a few changes in the Updater. The degeneration check and correction of IDS keys happens in 3.71 too now. Added code to download 3.90 PBP from the net via wifi. Note that his code is not yet 100% stable, it may crash when selecting AP. In that case, reinit the installer. L+triangle has been restored as method to bypass battery. If you already have 390.PBP keep those buttons pressed until you see "Verifying 390.PBP". If the 390.PBP is being downloaded via WiFi, press those buttons at the end of download until you see the previous sentence. A FW1.50 addon was also released the same day.
13 February 2008 Download: 
Improvements in plugin loading code. Added rest of the regions to fake region. (Korea, UK, East etc.) The 3.90 eboot downloading code is now more stable. On Slim: Added patches in nand ipl to allow Booster's Multi-IPL loader and TimeMachine ipl-loader to boot from nand. Note: only 3.90 M33-2 and higher can be booted from nand in slim with those ipl loaders, not official Sony firmwares or previous versions of M33. This also allows a PSP Slim to boot to the XMB with a Pandora Battery inserted.
31 March 2008 Download: 
March33 no-umd driver compatibiilty has increased to support games like Coded Arms, Patapon, Harvest Moon Innocent Life and probably others affected by same errors.
If you have came across this from a 4.00 M33 link, please note that there is no 4.00 M33 as 4.01 M33 was released.
June 28 2008 Download : 
Instead of Dark_Alex going ahead and release 4.00 M33, Sony released OFW 4.01. Therefore, Dark_Alex ended up releasing 4.01 M33 a few days later. New features included in this version is the usual features that 4.01 bring as well as the ability to translate the recovery menu configurable by a file that can be left on the memory stick or in flash1. Also, what would have been the GAME401 folder is now GAME4xx to acquaint for the future releases of any 4.xx firmware, and also previous 3.xx kernel homebrew. In the Camera mode from the XMB, the vshMenu was disabled since it interfered with the ability to change camera modes.
June 29 2008 Download : 
Released the day after the 4.01 M33 release, this fixed scePowerGetCpuClockFrequency that didn't allow for plugins and other homebrew to read the clock speed of the PSP correctly that first appeared in 3.80 M33-1. Also, bugs in recovery were fixed and the Spanish translation file was updated due to typos.
1.50 Kernel Addons
Ever since the release of 3.71 M33, it has been decided that the main installer should not install the 1.50 kernel addon like how it was in the OE firmwares, and the early M33 firmwares. The addon which is optional for Phat users allows users to install the 1.50 kernel for homebrew at the expense of the Location Free Player, and the Korean Font. However, the Location Free Player can be flashed back after the install. The addon will add the 'km', and 'podule' folders to flash0, where all of the 1.50 files will get flashed. Also, the installer has no checks so if there isn't no more space in flash0, the installer will end in an error, and you will have an incomplete, or no 1.50 subset.
There was two versions to the kernel addon released for 3.71 M33. The second version fixed the ipl issue where the 3.xx ipl will be active if the PSP was turned on from sleep mode. Instead of the 1.50 ipl being launched, it reverted back to 3.xx ipl and therefore froze the homebrew.
There was only one version of the kernel addon for 3.80 M33, and this mainly just added the 1.50 subset. There was no bugs needed to be fixed.
The 1.50 Kernel Addon for 4.01 M33 was released along with 4.01 M33-2. This is basically the same kernel addon that was released in the past adding 1.50 kernel support for Phats.