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PlayStation Architecture

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Re: PlayStation Architecture

#51

Post by knome »

corysama wrote: post #43
whizzter wrote: post #34

Earlier quoted context omitted.

You can see this on many consoles, iirc it basically just boils down to some address pins not being connected anywhere, so whatever the pins are set to doesn't matter as they're just out in the air so to say.

Then there’s the opposite situation. I knew the guys who ported NBA Jam: TE from arcade to PC (by hand-translating assembly!). Apparently the arcade CPU had bitwise addressing. And, because pretty much all of the data was aligned to bytes, the arcade programmers liked to stuff 3 bits of extra parameter data into the low bits of pointers.

it's not uncommon for runtimes to use always-zero bits from aligned pointers or bits above 48 (unused in most current 64bit CPUs) to store flags today. you don't need special 'bit-addressing' to do it. byte addressing works just fine.

Re: PlayStation Architecture

#52

Post by kalleboo »

whizzter wrote: post #34
boricj wrote: post #29

Earlier quoted context omitted.

Usually, that kind of stunt nowadays is done by using the lowest significant bits and masking them off when dereferencing the pointer, trading off for a higher alignment (so 4 bits gives you 16-byte alignment). The PS1 also happens to have RAM aliasing, because there's not enough RAM to cover the entire decoding window for the RAM. I don't know the details, but I've seen PS1 executables setting their stack pointer to…

You can see this on many consoles, iirc it basically just boils down to some address pins not being connected anywhere, so whatever the pins are set to doesn't matter as they're just out in the air so to say.

This was also done on the original Macintosh. The Motorola 68000 was a 32-bit CPU but only supported a 24-bit address bus, so the top bits were used by the OS as flags.

Then they released a new Mac with a 68020 that supported a 32-bit address bus and there was a multi-year process of making the OS and all the software "32-bit clean" to take advantage of it. There were 68020 Macs where the ROM in the machine itself wasn't even 32-bit clean and needed a software patch on boot.

Re: PlayStation Architecture

#53

Post by mrandish »

giancarlostoro wrote: post #24
kthartic wrote: post #12

Earlier quoted context omitted.

So? That was 5-7 years ago. I haven't seen this before, so I appreciate it being posted :)

Not only that, for a device from 1995... It's still amazing to learn about this, its not as if most people will read this once, and remember everything on the page in one go.

Check out the rest of Copetti's site. He's got similar posts on almost all the other consoles. So much gold.

Re: PlayStation Architecture

#55

Post by aidenn0 »

Narishma wrote: post #13
Scroll_Swe wrote: post #10

These articles are always excellent. PS1 games do not hold up so good, but PS2 games uprezzed to 1440p-4k are basically perfect imo.

They hold up pretty well when you play them as they were originally supposed to: on a CRT if you can or using emulators' CRT filters if you can't. Trying to play them at very high resolutions on crisp LCD displays is the worst way to go IMO.

I own a CRT and several playstation games. Many (most?) of the 3D games don't hold up that well. The aliasing artifacts are still quite visible and many games have occlusion bugs that TFA alludes to.

Re: PlayStation Architecture

#57

Post by mrandish »

ahartmetz wrote: post #41
babypuncher wrote: post #32

Earlier quoted context omitted.

What I find truly ironic is how CRT shaders work best on a 4k display with good HDR performance. 4k lets you scale the image and insert scanlines without scaling artifacts and with enough extra pixels to make the scanlines feel properly soft. HDR lets the shader compensate for the brightness lost to the CRT filter without desaturating the color.

While HDR is used to reproduce micro-patterns in brightness in such a configuration, I think CRTs would have been capable of HDR with appropriate control electronics since HDR requirements are basically: pixels can individually be set to very close to black and also to "pretty bright".

> I think CRTs would have been capable of HDR

Very likely. CRT technology from phosphors to screen masks to deflection yokes were highly-evolved but there was still a lot of headroom for more performance and new innovation. Some CRT tubes where capable of driving much higher brightness than their controllers ever allowed.

It's unfortunate that CRT manufacturing wound down entirely after ~2010. While the size, weight and huge glass volumes where impractical for mass-market consumer media devices, CRTs also had unique capabilities modern display tech still can't match. With all the current interest in retro CRTs, I actually looked into what it would take to do small runs of ultra high-end HD CRTs for collectors, almost on an artisanal boutique basis. Unfortunately, it looks like the upstream manufacturing chain of many component elements also collapsed because there were no other applications for them. So, the start-up costs to make the first one would be pretty huge.

Re: PlayStation Architecture

#58

Post by mrandish »

babypuncher wrote: post #32
Narishma wrote: post #13

Earlier quoted context omitted.

They hold up pretty well when you play them as they were originally supposed to: on a CRT if you can or using emulators' CRT filters if you can't. Trying to play them at very high resolutions on crisp LCD displays is the worst way to go IMO.

What I find truly ironic is how CRT shaders work best on a 4k display with good HDR performance. 4k lets you scale the image and insert scanlines without scaling artifacts and with enough extra pixels to make the scanlines feel properly soft. HDR lets the shader compensate for the brightness lost to the CRT filter without desaturating the color.

Fully reproducing the motion clarity of a CRT on a modern display also requires 480hz.

(https://blurbusters.com/crt-simulation-in-a-gpu-shader-looks...)

Re: PlayStation Architecture

#59

Post by userbinator »

malkia wrote: post #27

There are memory regions that are mapped to the same physical memory - https://psx-spx.consoledev.net/memorymap/ I worked on the Metal Gear Solid port from PSX to PC, and Konami programmers chose a wild trick to store how the "C4" bomb was planted - either on the wall, or on the ground. Essentially the pointer pointed to the same physical memory address, but if it was planted on the wall (or on the ground, I forgot)…

Early Macs used the upper byte of 32-bit pointers for other data:

https://en.wikipedia.org/wiki/Classic_Mac_OS_memory_manageme...

...and resulted in some models having a backwards-compatibility mode not too dissimilar to the PC's A20 gate, although for only a short period of time.

Re: PlayStation Architecture

#60

Post by pezezin »

Narishma wrote: post #13
Scroll_Swe wrote: post #10

These articles are always excellent. PS1 games do not hold up so good, but PS2 games uprezzed to 1440p-4k are basically perfect imo.

They hold up pretty well when you play them as they were originally supposed to: on a CRT if you can or using emulators' CRT filters if you can't. Trying to play them at very high resolutions on crisp LCD displays is the worst way to go IMO.

Nah, I was there a million years ago, and I always thought the PSX looked like crap compared to PC games of the era with their wobbly polygons and warping textures. And that is assuming that you were using SCART with a clean RGB signal, composite was even worse.
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