Earlier I discussed my plans for getting Daedalus's audio processing working on the PSP's Media Engine.

As I mentioned in that post, it's not just a case of changing some compiler setting to get this working. I've not spent much time investigating the ME so I may be wrong on a few of these points, but here are the current issues that I think need solving.

Firstly in order to access the ME I need to be running in kernel mode. This requires either running Daedalus in kernel mode, or (preferably) creating a kernel mode PRX that encapsulates the required functionality. I think kernel mode rules out anyone running with v1.50 firmware (hence my earlier post - please respond to the poll if you haven't already done so!) Maybe one of the more savvy psp developers out there can correct me on this? If no-one is using v1.50 any more then maybe it isn't even an issue.

Another problem is that although the ME is essentially the same processor as the main core, it has a different memory map. This means that things like the VRAM is invisible to the ME, so any code ported to run on the ME would have to be written to operate on main memory. This isn't an issue for Daedalus's audio list processing, but it would cause problems if I wanted to move display list processing to the ME too.

Touching on the memory map issue, another problem is the lack of cache coherency between the two cores. I need to be careful when accessing the same areas of memory with both cores to correctly flush and invalidate the data caches. Ideally any shared memory should be kept to a minimum, but this is easier said than done when porting existing code, rather than writing new code.

For a similar reason, any code which needs to run on the ME should avoid making any calls to the runtime library, including doing any system memory allocation. System calls are also ruled out. This is fairly easy to guarantee if you're writing new code, but again, it's a lot harder if you're porting existing code.

I think that's most of the issues from the hardware side. There are also a number of issues to be solved to do with the way that Daedalus handles audio and display list processing.

On the N64, the audio and display lists are processed asynchronously by the RSP coprocessor. In Daedalus, I can identify when these tasks are queued up for the RSP, intercept them, and process them synchronously (using high-level emulation rather than simulating the RSP execution directly).

The key thing here is that as far as the emulated N64 is concerned, audio and display list processing currently happens instantaneously. As soon as it kicks off the RSP it gets a interrupt to inform it that processing has completed. The whole process is very deterministic and I'm worried that by processing these display lists asynchronously on the ME that a number of intermittent and hard-to-debug issues will crop up. On the other hand, processing these tasks asynchronously is much closer to the behaviour of a real N64, which may fix some timing-related issues. It will also allow Daedalus to exploit the inherent parallelism that N64 roms were designed to take advantage of.

My current plan for ME audio support in R14 is:





Create a kernel mode PRX and get Daedalus successfully loading and invoking functions (under all supported firmwares). I've just about done this.

Add the code to support initialising and running code on the ME to the PRX. Test invoking user mode functions from the main EBOOT.PBP. I'll probably be using J.F.'s great sample code as a reference for this. Thanks J.F.!

Rewrite the audio list processing code so that it can be invoked synchronously or asynchronously as required (via some kind of configuration option). When running asynchronously it can just be run from a separate high-priority thread to start with. I can use this to test for various synchronisation issues without going through the pain of trying to do this on the ME first.

Audit the audio list processing code to minimise any memory accesses or ensure that they are correctly synchronised with the main core/thread. Any crt or system calls need to be eliminated or abstracted away (e.g. printfs NOP when compiled to run on the ME).

Invoke audio list processing code from the ME.

Cross fingers.



So, that's the plan; I'll keep you updated on my progress. If anyone has any experience doing this kind of thing on the ME it would be great to hear your thoughts.

-StrmnNrmn

PLEASE NOTE! This is NOT for 3.71+ Firmwares, but I will release a Version for those firmwares!

Allow me to introduce my next cheat device! This time it is for my favorite game series, Megaman X!

Allowing you to fly through levels, almost never die, and change weapons with the press of a button while playing as Vile, this Cheat Device is definitely worth a try!

Version 1 Info:
FlyMode - Allows you to easily fly around the level as X or Vile.
Infinite Health: You will never die! (Unless you fall down a hole or land on spikes)
Infinite Lives: You will always have 9 lives
Infinite Ammo: Infinite ammo for all weapons!
Always Charged Shots: All shots will be charged when the Square button is released!
Display Coordinates: Allows you to see your Coordinates while going through each level.
Vile's Weapon Changer: Allows you to go over budget and choose weapons you don't have. Even change them in the middle of a level!
Triangle for Hadouken: Hit Triangle to shoot the famous Hadouken, killing everything in its path, even Bosses!

Installation for OE and M33 Firmwares:
Installation:
Make a new folder named 'SEPlugins' on the root of your memory stick. In this new folder, drag
the MMMHXCD.prx file and make a new .txt file called 'Game.txt'. In this new .txt file, add this line:
ms0:/seplugins/MMMHXCD.prx

Save the .txt file. Now hold the power switch up until your PSP powers off. Turn it back on, hold the
Right Trigger down until you see the Recovery menu, then enable the PRX in the Plugins menu.

Cheat Device installed!

Over the past week I've started making plans for what I want to do for R14.

To start with, R13 introduced a couple of issues which I want to fix. Firstly, a number of roms now no longer work with dynarec enabled, or show odd behaviour. For instance, Aerogauge now finishes the race as soon as the countdown completes. I've tracked this down to one of the dynarec optimisations I added in August, where I optimise fragments which jump back to themselves. This should be a 'safe' transformation, so it suggests there's a bug somewhere in my implementation. If I can't fix the bug in time for R14, I'll add a temporary setting to allow this optimisation to be disabled on a rom-by-rom basis (much like the 'dynarec stack optimisation' setting).

Secondly, it looks like something I changed for savestate support has broken the 'return to main menu' option. I added some logic to help ensure that when taking a snapshot for the savestate, the CPU is paused in a 'safe' state (i.e. no dynarec code is executing, nothing is running on the RSP, and nothing is executing in the branch delay slot.) It looks like I've messed something up which is causing the 'return to main menu' option to wait for a safe state before bailing out to the menu. Should be an easy one to fix.

Morgan suggested a nice idea in the comments, which is that I generate a thumbnail for the savestate as it is created to display alongside the slot in the UI. It's a little tricky to implement, as by the time the emulator is told to create a savestate, it has already obliterated the n64's framebuffer with the Daedalus UI. I'll have to do something quite clever like speculatively copy the n64's framebuffer into system memory every time you enter the Pause Menu, or create the screenshot on the first frame rendered after saving. Either way, I'd like to add this simple feature to R14.

Next on my list for R14 is to look at making more significant performance improvements. Over the months many people have been asking when I'd get around to implementing audio on the PSP's Media Engine. I've talked about this before, but always kept putting it off in order to work on easier optimisations.

The Media Engine is a bit of unknown territory for me. Even though it's practically identical to the main CPU, you can't just change a setting an suddenly have your code running on it. There are a number of small hurdles I have to overcome before I can get audio working on the ME, but this is my big goal for R14 (I'll save the technical discussion for the next post.) If all goes to plan this should mean that audio can always be enabled without a significant impact on framerate.

So in summary for R14: a few bug fixes, thumbnails for savestates, and audio without affecting framerate.

-StrmnNrmn

I'm interested in which firmware everyone is running on. It would be very helpful if you could reply to this post with a) which model of PSP you're using ('fat'/slim, revision # if known) and b) which firmware you're using.

I have two PSPs. I have an original Japanese PSP with v1.00 firmware which I use for development, and a UK PSP which usually runs the latest official firmware (v3.72 at the moment.)

I'm interested because I want to know if anyone still requires the v1.50 (kxploit) versions of Daedalus that I release. I also need to figure out if it's worth my time getting a slim PSP for developing with the v3.xx+ firmware.

Thanks!
-StrmnNrmn