PS2 Is Virtual Memory Possible on PS2?

[PoyrazDereli]

Hi everyone,

You know, the Playstation 2 has low RAM... But someone seems to have overcome this... Also, you know him from the PS2 homebrew scene with projects like Athena, melonDS, and Enceladus.

I'm going to talk about a mod I've seen for a long time but didn't take seriously, thinking it was a scam. "GTA V Legacy" is a heavily modded version of GTA: San Andreas. I saw it for the first time in this video by Dr Mod. I realized that it's a really serious piece of work. There are very limited resources and tools available for modding GTA: SA on PS2.

For such heavy mods, it's necessary to increase the amount of RAM the game uses. In this video, he explains the plugin he wrote to manipulate the RAM. Unfortunately, I don't know Portuguese and I don't have programming knowledge. Is there anyone who can explain how he created the virtual RAM?

The expected question: Is it possible to increase the RAM of a Playstation 2 via an SSD disk using this method?

 

[Berion]

I'm not competent to answer that substantively but... Just thinking logical, we using RAM because it is super fast in write and access to it super fast. That's why at some stage on computers evolution, we specialized memory types. So for sure we cannot use eg HDD as RAM expanding and probably also there is no way on PS2 to expand RDRAM (DESR models have more but games not knows about that).

Maybe some caching is possible to actively swap needed data between slow storage and ram but that is question not only for programmer but reverse engineer, game hacker and someone who knows very well PS2 environment. I.e @uyjulian @krHACKen @El_isra

 

[Kevstah2004]

pcsx2 lets you expand the ram to suite developer units, I think they where codenamed TOOL? idk if it patches a retail bios too though.
If you hold down L1+L2+R1+R2 on startup on these bios you can set the region.

 

[PoyrazDereli]

I'm not competent to answer that substantively but... Just thinking logical, we using RAM because it is super fast in write and access to it super fast. That's why at some stage on computers evolution, we specialized memory types. So for sure we cannot use eg HDD as RAM expanding and probably also there is no way on PS2 to expand RDRAM (DESR models have more but games not knows about that).

Maybe some caching is possible to actively swap needed data between slow storage and ram but that is question not only for programmer but reverse engineer, game hacker and someone who knows very well PS2 environment. I.e @uyjulian @krHACKen @El_isra

Thank you for your valuable response. I don't have the expertise either; we can only speculate.

It's true that the HDD might be slow, but the PS2's RDRAM bandwidth is 3.2 GB/s (see https://www.psdevwiki.com/ps2/DRAM#RDRAM). With UDMA6 mode, theoretically 133 MB/s can be reached, which isn't bad for the PS2. (For SSD results: https://github.com/GrimBrew/PS2HDDTester#random-read-6mb-hdd---ee)

The video below proves that this can happen even via USB 1.1, which is the worst-case scenario:

Perhaps this virtual RAM could be used for external loaders (such as OPL, IGR, PADEMU, etc.). This way, it wouldn't put any load on the system (I'm just thinking, it might sound absurd).
Maybe there are better places where people knowledgeable about this could use it; I'm just wondering if something like this is possible.

@uyjulian @krHACKen @El_isra @sp193 (is alive?)

 

[El_isra]

This would eat IOP RAM, Wich is the most valuable resource while in-game on OPL or similar software

 

[PoyrazDereli]

This would eat IOP RAM, Wich is the most valuable resource while in-game on OPL or similar software

That's true, but it would only use the bandwidth of the IOP RAM. I don't think it would take up any space in physical memory.

Edit:
Another possible interpretation is that the amount of RDRAM available for games and programs to use via IOP will be expanded.

Edit 2:
In the comments on the video I shared above, someone mentioned that this method is used by some games on PS3 and Xbox 360 consoles (GTA V and FarCry 4), but no one has ever used it on PS2. This might be because the PS2 doesn't have internal storage.