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) - then it was OR-ing it with 80000000h or was A0000000h - or maybe something else - lol was long time ago.
It was fun porting this on PC, and right now I don't even remember what I did exactly - hahaha
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 the end of the devkit's 8 MiB of RAM and yet they work on retail units, because it ends up at the end of the retail's 2 MiB of RAM. So theoretically, you could stuff bits in there too (and without messing with different memory regions with different cache behaviors).
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.
You could do that on PC too, if you mmap() one given block of memory at multiple locations. I think that's how PS1 emulators handle mirroring (it's been a long time since I took a peek at the innards of DuckStation).
ha! I wish I knew this back then, but now I do remember - I think what we did was simply clearing the bit before access, and it was in just dozen or so places. Slap a macro and you are done!
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.
What a beautifully designed website. Everything is thoughtfully set-up and well placed. A great example of a well curated digital garden. It feels well kept and very human crafted.
Love Copetti. Even as someone who is not particularly knowledgeable of everything he’s talking about, I I really enjoy thumbing through his writing and diagrams. There’s just something really fun about trying to understand what is going on under the hood with these machines, especially fifth and sixth generation consoles
Copetti enjoyers should also checkout everything Fabien Sanglard has done, including the Wolfenstein and Doom Black Books, the Another World port analyses, and the other dozens of code reviews he's posted. https://fabiensanglard.net/
Executing the instruction after the jump seemed mental, but after a few days it was second nature. N64 had related issue: had to find an instruction to put between two multiplies. If the first multiple multiplied by zero or otherwise finished in two cycles, the CPU would freeze if the next instruction was also a multiply.
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.
It's interesting how different it is from the N64, which was seemingly designed to produce perfectly correct pixels even though no player would own displays that could really show the difference. I guess that's what you get when you let SGI design the GPU.
It probably had to do more with the evolution of chipset manufacturing and transistor counts (and costs).
The ps1 was released 1.5 years before the N64, the 3dfx voodoo chip is as capable as the n64 (maybe more so considering memory available), but I guess both Nintendo and Sony did opt for a bit more cost-efficient designs to make a profit on their consoles.
Looking at the release dates, the progression of capability is quite matched.
1994 dec 3 ps1
1995 nov 6 3dfx voodoo
1996 jun 23 n64
1998 nov 27 dc
2000 mar 4 ps2
Yeah, any 8/16-bit pixel are t wasn't made to be viewed on a screen with that high a resolution. CRTs smoosh/blur the image a bit so you don't see all the hardlines.
The PS1 didn't even have perpsective corrected texture mapping, some titles handled that manually to make it look less shit but not all titles did so.
The evolution of graphics was brutal in the 90s and early 00s, but somewhere around the PS3's appearance it slowed down since lighting models were becoming "good enough" on the PS3 for not being annoyingly bad and asset creation costs became the limiting factor rather than hardware.
> 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
On the emulator side I would definitely recommend Duckstation. It's performant, has great UI / UX and also has a CRT filter available by default that more or less recreates the original look, even slightly warping the image to make you feel like you are staring into a TV tube.
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".
Eeh ... speak for yourself. PS1 did mark the dawn of the 3D era for home consoles. There are lots of people who are into the low poly 3D models with the characteristic PS1 "wobble".
Sure a lot of it may be nostalgia but it does have its charm and I can say it's grown a lot on me over time. Especially once I learned about the PS1's unique hardware limitations. If my social media feed is anything to go by "PS1 graphics" are having a bit of a revival with lots of people trying to recreate that look.
Reportedly, the only location to store textures for quick GPU read access was a whole 4 KB in size. What an, apparently, dumb mistake. The blur was bad.
Graphically, either play on a CRT (or with CRT filters) or use an emulator that has PGXP geometry correction to eliminate vertex jittering at higher rendering resolutions.
As for gameplay, that console has a massive library, with thousands of commercially released games (and a lot of hidden gems). I'd be surprised if any gamer wouldn't find at least one to their taste in that catalog.
Yes an entire generation of games running on a mere 2MB of RAM and 1MB of VRAM.
The crazy thing too was how much a step up PS2 was compared to PS1 in terms of available compute and sheer horsepower. But even that wasn't enough for a sandbox game like GTA 3 to run without a lot of clever tricks [1]
Interesting video, we also made a PS2 game with streaming and fragmentation was definetly the worst part (as we also used Renderware) and funnily enough iirc the release version also had a built-in defragmentation system to move memory around (an annoying thing to do in C++ projects that weren't prepared for that from the start).
Did read this years ago and read it today again. Just so happy that there are people producing such quality work. Even if I personally don't know much about any of it, I still find myself being totally sucked in while reading.
43 comments:
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) - then it was OR-ing it with 80000000h or was A0000000h - or maybe something else - lol was long time ago.
It was fun porting this on PC, and right now I don't even remember what I did exactly - hahaha
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 the end of the devkit's 8 MiB of RAM and yet they work on retail units, because it ends up at the end of the retail's 2 MiB of RAM. So theoretically, you could stuff bits in there too (and without messing with different memory regions with different cache behaviors).
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.
You could do that on PC too, if you mmap() one given block of memory at multiple locations. I think that's how PS1 emulators handle mirroring (it's been a long time since I took a peek at the innards of DuckStation).
ha! I wish I knew this back then, but now I do remember - I think what we did was simply clearing the bit before access, and it was in just dozen or so places. Slap a macro and you are done!
This is great, but it was originally published in 2019. See the past discussions in 2020: https://news.ycombinator.com/item?id=22932134 (114 comments) and 2021: https://news.ycombinator.com/item?id=27576902 (114 comments also).
It’s been updated many times since then!
So? That was 5-7 years ago. I haven't seen this before, so I appreciate it being posted :)
Yep! Just that the post title should have a (2019) in it. Or maybe (2021) or (2025), given the most recent revision dates.
Fair enough!
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.
What a beautifully designed website. Everything is thoughtfully set-up and well placed. A great example of a well curated digital garden. It feels well kept and very human crafted.
Hey all, I posted this as I'm currently working on a PS1-related project that I hope to release soon.
Does anyone have recommendations for a PS1 web/js/wasm emulator? PCSX-Redux [0] has been great on desktop, and DuckStation [1] as well.
I found a few js/emscripten efforts, but if anyone has a rec, I'd appreciate it. Thanks!
[0] https://github.com/grumpycoders/pcsx-redux/
[1] https://duckstation.org/
Love Copetti. Even as someone who is not particularly knowledgeable of everything he’s talking about, I I really enjoy thumbing through his writing and diagrams. There’s just something really fun about trying to understand what is going on under the hood with these machines, especially fifth and sixth generation consoles
Copetti enjoyers should also checkout everything Fabien Sanglard has done, including the Wolfenstein and Doom Black Books, the Another World port analyses, and the other dozens of code reviews he's posted. https://fabiensanglard.net/
1994 always gets me too. It feels like they are more a late 90s thing.
They didn't launch outside of Japan until late 1995, so most people got one in '96.
Which means that we're really talking about hardware from 91-93, right? I.e. if launch was 94 then they were designing in 91-93ish.
PS2 didn't come out until 2000. Most of the games I remember are from later too.
Executing the instruction after the jump seemed mental, but after a few days it was second nature. N64 had related issue: had to find an instruction to put between two multiplies. If the first multiple multiplied by zero or otherwise finished in two cycles, the CPU would freeze if the next instruction was also a multiply.
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.
It's interesting how different it is from the N64, which was seemingly designed to produce perfectly correct pixels even though no player would own displays that could really show the difference. I guess that's what you get when you let SGI design the GPU.
It probably had to do more with the evolution of chipset manufacturing and transistor counts (and costs).
The ps1 was released 1.5 years before the N64, the 3dfx voodoo chip is as capable as the n64 (maybe more so considering memory available), but I guess both Nintendo and Sony did opt for a bit more cost-efficient designs to make a profit on their consoles.
Looking at the release dates, the progression of capability is quite matched.
1994 dec 3 ps1 1995 nov 6 3dfx voodoo 1996 jun 23 n64 1998 nov 27 dc 2000 mar 4 ps2
Yeah, any 8/16-bit pixel are t wasn't made to be viewed on a screen with that high a resolution. CRTs smoosh/blur the image a bit so you don't see all the hardlines.
The PS1 didn't even have perpsective corrected texture mapping, some titles handled that manually to make it look less shit but not all titles did so.
The evolution of graphics was brutal in the 90s and early 00s, but somewhere around the PS3's appearance it slowed down since lighting models were becoming "good enough" on the PS3 for not being annoyingly bad and asset creation costs became the limiting factor rather than hardware.
> 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
On the emulator side I would definitely recommend Duckstation. It's performant, has great UI / UX and also has a CRT filter available by default that more or less recreates the original look, even slightly warping the image to make you feel like you are staring into a TV tube.
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".
> PS1 games do not hold up so good
Eeh ... speak for yourself. PS1 did mark the dawn of the 3D era for home consoles. There are lots of people who are into the low poly 3D models with the characteristic PS1 "wobble".
Sure a lot of it may be nostalgia but it does have its charm and I can say it's grown a lot on me over time. Especially once I learned about the PS1's unique hardware limitations. If my social media feed is anything to go by "PS1 graphics" are having a bit of a revival with lots of people trying to recreate that look.
I had the N64. It did not wobble. Seeing a Playstation in action with its wobble was so weird.
N64 didn't have the wobble, but it definitely had the blur.
Reportedly, the only location to store textures for quick GPU read access was a whole 4 KB in size. What an, apparently, dumb mistake. The blur was bad.
Graphically, either play on a CRT (or with CRT filters) or use an emulator that has PGXP geometry correction to eliminate vertex jittering at higher rendering resolutions.
As for gameplay, that console has a massive library, with thousands of commercially released games (and a lot of hidden gems). I'd be surprised if any gamer wouldn't find at least one to their taste in that catalog.
It is quite amazing to me to see the specs and what developers managed to squeeze out of that!
Yes an entire generation of games running on a mere 2MB of RAM and 1MB of VRAM.
The crazy thing too was how much a step up PS2 was compared to PS1 in terms of available compute and sheer horsepower. But even that wasn't enough for a sandbox game like GTA 3 to run without a lot of clever tricks [1]
[1] https://youtu.be/cIbCxbrBCys?si=cLMr4-7ubGD4fNWi
Interesting video, we also made a PS2 game with streaming and fragmentation was definetly the worst part (as we also used Renderware) and funnily enough iirc the release version also had a built-in defragmentation system to move memory around (an annoying thing to do in C++ projects that weren't prepared for that from the start).
The 2D ones (e.g. Symphony of the Night) do.
Love the 2D games of the PS1 era. I still replay Mega Man X4/5/6 every once in a while.
I love a pre-Claude article
Did read this years ago and read it today again. Just so happy that there are people producing such quality work. Even if I personally don't know much about any of it, I still find myself being totally sucked in while reading.
I love his work. I bought one of his books recently :)