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Why can the PS Vita emulate PSP games as well as it does?

Open discussions on programming specifically for the PS Vita.
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endrift
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by endrift » Mon Nov 24, 2014 1:21 am

yifanlu wrote:Vita doesn't emulate PSP. There's a PSP CPU inside the Vita. They can do it because it's cheap and small. Isn't technology amazing?
I'd been wondering about this for quite awhile. It's the classic Nintendo approach, but everyone seemed to think there wasn't an Allegrex chip in the Vita. I guess that explains why Kermit works entirely by message passing.
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by yifanlu » Mon Nov 24, 2014 1:42 am

In hindsight everything seems more obivous. Like, why would they use a serial communications protocol if it's just in software? Why go through the overhead of serializing data and then immediently unserializing when they could have some something simple like a shared memory buffer. Of course if the serial data actually passes through a serial port... Then it makes sense.
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by josh_axey » Mon Nov 24, 2014 2:43 am

So the final question: softcore IP 4xxx Allegrex-like on ASIC - or re-engineered 4xxx Allegrex-like MIPS unit?
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by thedicemaster » Mon Nov 24, 2014 8:56 pm

Conjo wrote:
Ruben_Wolfe wrote:
yifanlu wrote:Vita doesn't emulate PSP. There's a PSP CPU inside the Vita. They can do it because it's cheap and small. Isn't technology amazing?
Ha, always wondered about it since I saw a discussion about whether the psp emulation is achieved by software/hardware.
Good to finally know for sure.
Can you tell why the emulator is that of a psp 1000?(32MB ram)
Is there really any good reason for sony to limit it's ram from 64 to 32?
I don't think there is a good reason to have 64 mb, since I think those 32 mb extra are only useful for homebrews and games don't really need them (at least not the games in the store)
if i remember correctly the vita actually used to emulate a 2/3k but they limited the memory to 32MB to discourage use of VHBL/eCFW

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Re: Why can the PS Vita emulate PSP games as well as it does

Post by MooMooMan » Tue Nov 25, 2014 3:01 am

There is no reason for the Vita to have 64MB in the emulation. No games that I know of supported or made use of 64MB memory. You could, however force all games to allocate the memory if you have 6.60CFW on your PSP, I think it's PRO C that added support for it. But yeah, no official titles that I know of actually made use of the extended memory, which is most likely why Sony chose to only include 32MB. That could also make it harder for those trying to exploit the PSP emulator, since they don't have as much memory to work with.
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by Mathieulh » Tue Nov 25, 2014 2:17 pm

yifanlu wrote:Vita doesn't emulate PSP. There's a PSP CPU inside the Vita. They can do it because it's cheap and small. Isn't technology amazing?
I have always suspected so myself, It's just rather impossible to confirm short of decapsulating the Vita CPU or reverse engineering the pspemu binaries.
The pspemu "cpu" even handles undocumented instructions so it was my fair assumption that there is a real one hidden somewhere in the SOC.
I do not believe everything is hardware though, it seems likely that things such as Kirk (which uses different sets of keys on vita) or the ME are emulated through software. I've never had any time to look further into this myself.
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by Proxima » Tue Nov 25, 2014 3:35 pm

Pretty much unless it goes through a Kermit interface, its hardware. When you say "different keys" what are you talking about?

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Re: Why can the PS Vita emulate PSP games as well as it does

Post by Mathieulh » Tue Nov 25, 2014 8:12 pm

Proxima wrote:Pretty much unless it goes through a Kermit interface, its hardware. When you say "different keys" what are you talking about?

Thanks!
Some of the kirk seeds are different as far as I know of (as in, some kernel modules will not decrypt on psp if I recall properly)
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by qwikrazor87 » Tue Nov 25, 2014 8:18 pm

Mathieulh wrote:Some of the kirk seeds are different as far as I know of (as in, some kernel modules will not decrypt on psp if I recall properly)
hmm, so far I've been able to decrypt every flash module with the PSP from the ePSP, just need to update the keys when they update the module tag, I could be mistaking you for talking about something else, don't mind me.
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Re: Why can the PS Vita emulate PSP games as well as it does

Post by Mathieulh » Tue Nov 25, 2014 8:34 pm

qwikrazor87 wrote:
Mathieulh wrote:Some of the kirk seeds are different as far as I know of (as in, some kernel modules will not decrypt on psp if I recall properly)
hmm, so far I've been able to decrypt every flash module with the PSP from the ePSP, just need to update the keys when they update the module tag, I could be mistaking you for talking about something else, don't mind me.
Hum... I must be misremembering as well, it's been way too long since I looked into any of this.
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