I’ve used quite a few hardware dev kits in my time. These early dev kits are prototypes —- released long before the hardware or industrial design is finalized. They are made in small batches, often by hand (with bodge wires everywhere), and are highly optimized for disassembly, debugging, and troubleshooting. They often have tons of ports.
Early Xbox 360 dev kits were literally a PowerMac G5 with some customizations. Early Dreamcast dev kits were in a mini tower case. Frankenstein appendages are common especially for exotic hardware. I remember using an early Haswell dev kit which was a huge plexiglass monstrosity with a capacitive touchscreen glued to the top. (A later dev kit had a much more manageable iPad-like form factor.)
As you can imagine these dev kits are expensive and rare. The hardware manufacturer will want these early dev kits they loan back, and they are almost always destroyed. (A few may slip through the cracks which is how unicorn find like the Nintendo PlayStation prototype was found a few years back.)
As the hardware coalesces and goes through the various development stages, subsequent dev kits typically become smaller and more manageable. In some cases they may be nearly indistinguishable from retail hardware without closer inspection.
I'll add that initial dev kits are typically released 18 months before the console launch, that means they are built using technology that is one generation behind the hardware that the actual console will use. In the old days before Moore's Law ended, that meant that the console had to have a much more expensive CPU and GPU, to try to match the expected performance of the console hardware. These days, with only marginal improvements in CPU and GPU from generation to generation, this is much less of an issue.
Fun fact: The PowerMac G5 CPU cooling fan controllers have a failsafe mode: If the OS doesn't communicate with the fan controller, the fan controller assumes the worst: that the CPU is switched into the most power-hungry mode possible. To prevent potential damage to the CPU, after about 30 seconds, the cooling fans are cranked up to extraordinarily loud levels.
Apple didn't document how to control the fans. It took Microsoft a while to reverse-engineer the fan controllers. During that time period, using the G5s as Xbox dev kits required putting up with extraordinarily loud fans.
I can't find the photo with a quick google, but way back in the day an employee posted a photo of a TON of G5s arriving at Microsoft HQ.. supposedly they got fired for it, and it wasn't until a year or two later when the 360 was announced that everyone put two and two together.
Hundreds of comments, apparently this news went around the world. I assume they thought at the time the Macs were needed for developing MS Office for Mac OS.
I absolutely love how Sony then trampled over Nintendo by first using their experience from this collaboration to make their own PS, then basically cloned the N64 architecture in the form of PS2.
Sony didn't want anything to do with this project. This was all Ken Kutaragi's ambition, and after the Nintendo disaster he joined forces with the Sony Music side of the business (!) to form Sony Computer Entertainment, and was basically given full autonomy to launch his console. Sony Music knew retailers, knew how licensing worked, and knew how to take advantage of Nintendo's greed by undercutting their margins.
I don't know whether they had lower margins, but they used CDs, which were cheaper to produce than the ROM chips which were so far common for consoles (N64, SNES, Mega Drive, NES, ...). The price of those did go down a lot over time (early NES cartridges had 4 KB, early N64 cartridges 8 MB, a 2000 fold increase), but not quite quick enough apparently. High cartridge prices were not limited to Nintendo.
Were there really significant similarities between the N64 and the PS2 architectures? My understanding is that all the "first generation 3D consoles" had substantial weaknesses in their architecture, due to lack of experience, which were ironed out in the next generation.
They weren't identical, but they sure stood apart from others. Both used 64-bit MIPS CPUs, both had dedicated 128-bit SIMD cores driving their display list based GPUs. For a 1996 N64 having a SSE2 level SIMD was absolutely amazing. They're even similar from emulation standpoint: only in the last decade we've got enough CPU power to consistently emulate them at full speed.
Early Xbox 360 dev kits were literally a PowerMac G5 with some customizations. Early Dreamcast dev kits were in a mini tower case. Frankenstein appendages are common especially for exotic hardware. I remember using an early Haswell dev kit which was a huge plexiglass monstrosity with a capacitive touchscreen glued to the top. (A later dev kit had a much more manageable iPad-like form factor.)
As you can imagine these dev kits are expensive and rare. The hardware manufacturer will want these early dev kits they loan back, and they are almost always destroyed. (A few may slip through the cracks which is how unicorn find like the Nintendo PlayStation prototype was found a few years back.)
As the hardware coalesces and goes through the various development stages, subsequent dev kits typically become smaller and more manageable. In some cases they may be nearly indistinguishable from retail hardware without closer inspection.