Powermac G4
Apple's PowerMac G4 "MDD" or "Mirrored Drive Door" units are common enough and have been documented heavily enough across the internet by people smarter than me that I don't have much to add about them here.
I currently own two units. A Dual 1.42Ghz "Firewire 800" (FW800) model and a Dual 1.25Ghz FW800 model.
1.42Ghz model details
This machine is outfitted with the maximum 2GB of memory (1.5GB under MacOS 9.2) and the fastest supported GPU, an Nvidia Ti4600
The 1.42Ghz model is also equipped with a SeriTek/1eVE2+2 expansion card. This card appears(?) to have been discontinued as the SeriTek "Yahoo" store is no longer operational.
The SeriTek card provides a 64-bit PCI-X (266MB/s) interface for attaching two SATA II hard disks. The PCI-X bandwidth allows attached drives to operate near their theoretical maximum of 300MB/s (SATA II 3Gbps) however in operation due to the old, slow G4 CPU typical data transfer rates are roughly half that. This is still considerably faster than the ATA-66 IDE bus installed on the motherboard as standard.
The SeriTek card also contains an OpenFirmware compatible Boot ROM, allowing the card to be used to boot OS 9 natively. The additional I/O performance massively improves I/O bound workloads such as "StuffIt" and heavier apps such as ClassZilla.
The internals of the 1.42Ghz model have also been modified. The power supply has been replaced with a PicoPSU style unit for ATX PC's (with corresponding adapter cable) along with dual Noctua 40mm fans for additional cooling. The main CPU fan has been replaced with a 120mm Noctua "PPC" Industrial fan. This fan outputs considerably more airflow than the original fan, while maintaining comparable noise levels. The CPU has yet to be measured above 35C while in operation under this configuration.
At this time the machine currently operates with MacOS 9.2 and OS X 10.5.9 "Sorbet Leopard" from a 240GB SSD partitioned 50/50 between the two operating systems
The second port was originally configured with a second 120GB drive for PPC Linux. However the "nouveau" Linux driver causes system lockups due to (known) endianness issues on PowerPC platforms
1.25Ghz model details
This machine is currently unused and lacks a graphics card. It was purchased for testing upgrading the Xserve G4 with a faster dual processor CPU however this was unsuccessful.
The unit has a SCSI card of currently known vendor as well as a dual gigabit PCI-X SFP NIC of unknown vendor
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