Comment by Grazester
9 hours ago
By the way, the AMD athlon 64-bit launched 2003. The PS3 launched in 2006. I had an AMD64 bit process in my laptop in 2005.
What wasn't viable?
9 hours ago
By the way, the AMD athlon 64-bit launched 2003. The PS3 launched in 2006. I had an AMD64 bit process in my laptop in 2005.
What wasn't viable?
Yeah that part didn't make sense, not to mention that neither the PS3 nor the 360 were running 64-bit software. They didn't have enough memory for it to be worth it.
you don't need memory to make 64 bit software worth it. Just 64 bit mathematics requirements. Which basically no video game console uses as from what I understand 32-bit floating point continue to be state of the art in video game simulations
Fundamentally it's still a memory limitation, just in terms of memory latency/cache misses instead of capacity. If you double the size of your numbers you're doubling the space it takes up and all the problems that come with it.
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Parts of the 360 did. The hypervisor ran in 64bit mode, and use multiple simultaneous mirrors of physical address space with different security properties as part of its security model.
It's not like the games weren't running in 64 bit mode too (on both consoles)
They had full access to the 64 bit GPRs. There wasn't anything technically stopping game code from accessing the 64 bit address space by reinterpreting a 64 bit int as a pointer (except that nothing was mapped there).
It's only the pointers that were 32 bit, and that was nothing more than a compiler modification (like the linux x32 ABI).
They did it to minimise memory space/bandwidth. With only 512 MB of memory, it made zero sense to waste the full 8 bytes per pointer. The savings quickly add up for pointer heavy structures.
I remember this being a pain point for early PS3 homebrew. Stock gcc was missing the compiler modifications, and you had a choice between compiling 32 bit code (which couldn't use the 64bit GPRs) or wasting bandwidth on 64 bit pointers (with a bunch of hacky adapter code for dealing 32 bit pointers from Sony libraries)
I have some confidence that AMD's acquisition of ATI had a huge impact.
That allowed both a CPU and an advanced GPU to be on the same die.
They also wisely sold Global Foundries, and were able to scale with TSMC.
Because consoles don't use off-the-shelf CPUs for many reasons. Neither Intel nor AMD of that time would even consider making a bespoke CPU for Sony or MS.
Even they could use off-the-shelf SKU it wouldn't be viable - neither one had one that fits in power envelope (not that it helped xbox...)
Consoles used off-the-shelf CPUs until the 6th generation. Even the Dreamcast and the first Xbox used off-the-shelf CPUs, it was only the PS2 and the GameCube that started the trend of using custom-made CPUs.
Not entirely accurate.
The PSX's CPU is semi-custom. The core is a reasonably stock R3000 CPU, but the MMU is slightly modified and they attached a custom GTE coprocessor.... I guess you can debate if attaching a co-processor counts as custom or not (but then the ps4/xbone/ps5/xbs use unmodified AMD jaguar/zen2 cores)
IMO, the N64's CPU counts as off-the-shelf... however the requirements of the N64 (especially cost requirements) might have slightly leaked into the design of the R4300i. But the N64's RSP is a custom CPU, a from scratch MIPS design that doesn't share DNA with anything else.
But the Dreamcast's CPU is actually the result of a joint venture between Hitachi and Sega. There are actually two variants of the SH4, the SH4 and SH4a. The Dreamcast uses the SH4a (despite half the documentation on the internet saying it uses the SH4), which adds a 4-way SIMD unit that's absolutely essential for processing vertices.
We don't know how much influence Sega's needs had over the whole SH4 design, but the SIMD unit is absolutely there for the Dreamcast, I'm pretty sure it's the first 4-way floating point SIMD on the market. The fact that both the SH4/SH4a were then sold to everyone else, doesn't mean they were off the shelf.
Really, the original Xbox using an off-the-shelf CPU is an outlier (technically it's a custom SKU, but really it's just a binned die with half the cache disabled).
They would have started designing the systems in 2003, and one of the first choices is CPU partner.
Do you trust the new line of CPUs that just launched that year?
You have to remember that the AMD and Intel of today are very different companies than they were 20-25 years ago. AMD split off it's fab capabilities, acquired ATI, adopted TSMC as a fab, and developed a custom silicon business.
At that time AMD wasn't in the custom CPU business, AMD64 was a new unproven ISA, and x86 based CPUs of that time were notoriously hot for a console. These were also some of the reasons why Microsoft moved away from the Pentium III it had used in the original Xbox.
The PS3 was launched in 2006 but the hardware design was decided years earlier to provide a reference platform for the software.