osx tiger doesnt know pcie2.0 but it works because of backward compatibility

[chrisNova777]

does osx tiger support PCIE 2.0?
Technically, Mac OS X Tiger does not have native support for PCIe 2.0, because the hardware it was designed for simply didn't use it yet.

However, in the world of vintage workstations and Hackintoshes, the answer is a bit more nuanced.

1. The Official History
When Tiger (10.4) was released and during its primary update cycle (up to 10.4.11), Apple’s professional hardware was transitioning from PCI-X to PCIe 1.1:

Late 2005 Power Mac G5: These were the first Macs with PCIe, and they used PCIe 1.1.

2006/2007 Mac Pro (1,1 and 2,1): These also used PCIe 1.1.

PCIe 2.0 didn't arrive in the Mac world until the Early 2008 Mac Pro (3,1), which shipped with Mac OS X 10.5 Leopard.

2. Does it work in your G41 / AMD builds?
Yes, it will "work," but not because Tiger knows what PCIe 2.0 is. It works because of hardware backward compatibility:

The "Invisible" Speed: If you put a PCIe 2.0 card into your Asus M4A785TD (which is a PCIe 2.0 board), the hardware negotiates that 2.0 speed at a level below the operating system. Tiger just sees a generic "PCI Device."

No Software Benefit: Tiger doesn't have the updated drivers or kernel optimizations to specifically take advantage of PCIe 2.0 features (like advanced power management or certain high-end graphics calls). It treats the bus as a very fast pipe, but it doesn't "know" it's 2.0.

3. Potential Issues
If you are pushing Tiger onto a PCIe 2.0 system, keep these two things in mind:

GPU Drivers: This is the biggest hurdle. Most PCIe 2.0 graphics cards (like the NVIDIA 8000/9000 series or ATI HD 4000 series) do not have drivers for Tiger. You are usually stuck using PCIe 1.0/1.1 era cards (like the NVIDIA 7000 series or ATI X1900) even if the slot is 2.0.

Bus Errors: Occasionally, very early versions of Tiger (like 10.4.4 or 10.4.7) can get "confused" by modern PCIe bridges on newer motherboards, leading to kernel panics during boot. Stick to 10.4.11 for the best chance of stability on that Asus board.

The Verdict: Tiger will run on a PCIe 2.0 motherboard and will benefit from the extra bandwidth for things like disk controllers, but it won't officially "recognize" the standard. It's essentially "over-provisioning" the OS with more speed than it was ever programmed to expect.

[chrisNova777]

does leopard know what pcie 2.0 is?
Yes, Leopard (10.5) definitely "knows" what PCIe 2.0 is, unlike Tiger.

While Tiger was a transition OS that just happened to run on early PCIe hardware, Leopard was the first version of Mac OS X to ship on machines that officially supported and advertised the PCIe 2.0 standard.

1. The Arrival of "Native" Support
PCIe 2.0 support was introduced to the Mac lineup with the Early 2008 Mac Pro (3,1). This machine shipped with Mac OS X 10.5.1. Because this hardware featured two PCIe 2.0 x16 slots, Apple had to update the kernel and the IOPCIFamily.kext (the driver that manages the PCI bus) to handle the increased link speeds and power requirements.

2. Visible Differences in Leopard
If you are running Leopard on your Asus M4A785TD-M EVO (which is a PCIe 2.0 board), you will see better integration than in Tiger:

System Profiler Recognition: In Leopard, if you go to About This Mac > More Info > PCI Cards, the OS is much better at identifying the link speed (5.0 GT/s) and the current lane width (x1, x4, x16) of your devices.

Driver Availability: Leopard was the era where "modern" PCIe 2.0 GPUs arrived. Cards like the NVIDIA 8800 GT and ATI Radeon HD 4870 required Leopard (specifically 10.5.2 or later) because their drivers were built around the PCIe 2.0 architecture.

3. Practical Impact for Your Builds
Feature   OS X Tiger (10.4)   OS X Leopard (10.5)
PCIe 2.0 Status   Accidental. Works via hardware backward compatibility.   Intentional. Kernels and drivers updated for the standard.
GPU Selection   Very limited (mostly PCIe 1.1 era cards).   Much broader (supports Early 2008/2009 era 2.0 cards).
Stability   Occasional bus errors on newer boards.   High stability on PCIe 2.0 chipsets.
Disk Performance   Same as Leopard (Hardware-bound).   Same as Tiger (Hardware-bound).
The "Compatibility Trick"
Because you’re switching between boards like the Gigabyte G41 (PCIe 1.1) and the Asus M4A785 (PCIe 2.0):

Leopard is the "Bridge" OS: If you want a dual-boot system, Leopard is much more comfortable on that Asus board. It won't get "confused" by the newer chipset features as easily as Tiger might.

Expansion Cards: If you use a PCIe 2.0 SATA III card, Leopard’s updated PCI family drivers ensure the card is initialized correctly at its full 5.0 GT/s speed without needing third-party patches to the "IOPCI" system files.

The Verdict: If your goal is the absolute "Ultimate" performance for a mid-2000s workstation, Leopard is the first OS that is truly "aware" of the hardware speeds your Asus board can provide.

[chrisNova777]

so my P5B Deluxe Wifi/AP will never be enough for Snow Leopard true potential without pcie 2.0 support??

That is a bittersweet realization for many LGA775 enthusiasts. The Asus P5B Deluxe is a legendary board—arguably one of the best ever made for overclocking—but you’ve hit on its one "hard" ceiling: it is an Intel P965 chipset board, which means it is strictly PCIe 1.1.

Even if you have the fastest Core 2 Quad and 8GB of RAM, you are effectively running Snow Leopard on a highway with a lower speed limit than your Asus M4A785TD-M EVO or a late-model Mac Pro.

Why the P5B Deluxe Hits a Wall in Snow Leopard
The "True Potential" of Snow Leopard relies on high-speed data movement, and the P5B Deluxe has three specific bottlenecks compared to a PCIe 2.0 board:

1. The GPU "Choke" Point
Snow Leopard introduced Core Animation and OpenCL everywhere. These technologies constantly move textures and data between the System RAM and the GPU.

PCIe 1.1: Has a bandwidth of 250 MB/s per lane.

PCIe 2.0: Doubles that to 500 MB/s per lane.
If you’re using a high-end card like an NVIDIA GT 120 or an ATI 4870 (popular Snow Leopard cards), the P5B Deluxe forces that card to work with half the available "breathing room" for the bus. You might notice slight micro-stutters in the UI that wouldn't exist on a 2.0 board.

2. The SSD "Glass Ceiling"
As we discussed with your other boards, a modern SATA III SSD on a PCIe expansion card is a night-and-day difference for Snow Leopard's boot times and app launches.

On the P5B Deluxe, a PCIe x1 SATA card will max out at ~200-220 MB/s because of PCIe 1.1 overhead.

On a PCIe 2.0 board, that same card hits ~400-500 MB/s.
Snow Leopard loves fast "random access" speeds, and the P5B Deluxe simply can't let a modern drive stretch its legs.

3. The Southbridge (ICH8R)
While the P5B Deluxe was great because it supported AHCI (unlike the G41 board), its internal communication between the CPU and the various ports (USB, SATA, Ethernet) is handled via the DMI (Direct Media Interface), which on the P965 chipset is equivalent to PCIe 1.1 speeds. When you’re pushing the system hard—say, recording audio while moving files—the bus gets crowded much faster than on 2.0-era chipsets.

The Silver Lining: Why the P5B Deluxe is still "Great"
Even if it isn't "True Potential" in terms of raw bandwidth, the P5B Deluxe has one thing the G41 doesn't: Stability and Compatibility.

Native AHCI: Unlike your G41MT-S2PT, the P5B Deluxe has a proper Intel ICH8R controller. Snow Leopard "sees" this natively, making it one of the most stable Hackintosh builds ever.

Overclocking: You can often push an E8600 or a Q9650 much higher on a P5B Deluxe than on almost any other board, which can sometimes compensate for the slower PCIe bus in CPU-heavy tasks.

Comparison: Performance Ceiling
Feature   P5B Deluxe (P965)   Asus M4A785TD (785G)
Max Disk Speed (PCIe)   ~220 MB/s   ~500 MB/s
GPU Bus Width   PCIe 1.1 (Slower)   PCIe 2.0 (Faster)
OpenCL Performance   Limited by Bus   Optimal
"Feel" in Snow Leopard   Smooth   Snapdragon-fast
The Verdict: You’re right. The P5B Deluxe is a "Formula 1 car from 2006." It’s amazing, but Snow Leopard is a "2009 track." To see what the OS is truly capable of when it's fully "unleashed," you need that PCIe 2.0 bandwidth.