Powermac G5
Apple's G5 Powermac's are rather infamous, being Apple's "last gasp" of PowerPC. The PowerMac G5 Quad in particular is easily among Apple's most unloved and slapdash engineered products.
Due to me taking the suggestion of a friend far too literally (ilu Ben please don't hate me) I own seven G5 Quads
Despite this only one of them is functional!
All Mac G5 Quads were made with "water cooling" loops, due to the thermal output of the CPU's at the time. (105 watts of heat in 2005 is a lot, though with what Intel puts out these days seems rather pedestrian!) however calling it water cooling is incorrect. It's actually radiator fluid! Specifically "Dex-Cool" or AntiFreeze.
The water cooling loops were designed and manufactured by American car maker GM Auto's engine radiator subsidiary. Your G5 Mac literally uses car parts to cool its CPU's! It's any wonder Apple ditched IBM.
It's possible (and desirable) to replace the entire cooling assembly, the 68KMLA forms calls it the "New Blood Mod" though I have not yet performed the repairs on my units due to cost.
Anyway. The one singular G5 Quad I have working is effectively a maxed out G5 Quad. The specifications are listed below
4x 2.5Ghz PPC64 G5 CPU's (2c/2t)
16GB DDR2-667 (or 800? I forget the max speed) RAM. In theory the chipset can support 32GB but nobody has managed to get one operating with that much memory.
Two 240GB SATA SSD's. Due to Apple's flaky SATA controller most drives won't work as negotiating SATA 3 speeds down to SATA 1 causes the controller to instead hang. You may want to find drives that have a SATA1 jumper option to prevent this!
As the G5 Quad contains four PCI-E slots (of varying bandwidths) I've arranged them as follows
240GB NVME drive via PCI-E adapter (PCI-E x4)
10G Intel X520 SFP ethernet adapter (PCI-E x8)
Slot blocked by dual-slot GPU (PCI-E x8 otherwise)
ATI Radeon X1950 (vBIOS flashed for Mac operation)
The NVME drive is purely used for Linux. GRUB will load a kernel from the SATA drive and is configured to pass root=/dev/nvme0n1p1 allowing the root filesystem to be run off NVME. As a bonus, moving the Mac "k2_sata" kernel module to be loaded on-demand instead of at boot will save 5 seconds off the Linux kernel boot time.
The system currently dual boots OS X 10.5.9 "Sorbet" Leopard and Gentoo PPC64
Unfortunately G5 Quads cannot run Tiger due to missing fan control drivers. If installed, the fans will eventually ramp to 100% as a failsafe mechanism.
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