PowerMac compatible PCI-X (64bit) extension cards

[Elosha]

Good day,

I'm wondering about the 64bit wide PCI slots in my PowerMac G3/G4 ("Yikes", "Sawtooth" etc.).

• I am aware that 64bit PCI predates PCI-X. But PCI-X cards are heavily backward-compatible regarding voltage, bus width, bus speed and even PCI vs. PCI-X specification. Specs claim you may even use them inside a 5V 32bit PCI slot!
• Also I have come accross a broad variety of cards that even match Mac OS X's available kernel drivers.
• However, if I insert one of these cards, like an active Broadcom Gigabit NIC, nothing happens at best, and the system crashes at worst.
  (A brand new, boring, passive Realtek 32bit PCI Gigabit card however just works …)

My only 64bit PCI card that actually works is the Adaptec AHA-29160 Mac variant that came with the high-end G3.

What are your experiences?

 

[joevt]

I would like a 64-bit PCI-X to PCIe bridge so I could try getting more than 133 MB/s from a PCIe device in a Yosemite/Yikes (266 MB/s). The Mac with the fastest PCI-X slot is the Power Mac G5 (PCI-X) (1067 MB/s).
https://forums.macrumors.com/thread...l-work-in-a-beige-power-macintosh-g3.2303689/

The Yosemite/Yikes has a 66 MHz 32-bit slot which has similar performance to the 33 MHz 64-bit slot (266 MB/s) but I haven't found a benchmark that can measure > 133 MB/s
https://forums.macrumors.com/thread...nfo-and-experimentation.2428884/post-33206243

An AGP 8x slot can do 2133 MB/s but getting a bridge that can do more than AGP 1x is near impossible and PCI-X to PCIe bridges are mostly/all? limited to 2.5 GT/s x4 = 1000 MB/s.

I have a fork of pciutils on github that works in Mac OS X on PowerPC Macs. Alternatively, I have a script that can gather PCI info from Open Firmware for lspci of pciutils to parse.

 

[Elosha]

The fact about 32bit/66MHz vs. 64bit/33MHz is interesting, makes sense.

Would be happy if any 64bit stuff just worked in these slots – I mean what's the reason they are there. Adapting to higher speed buses is another level.

I remember looking at the archived OWC website – they were not recommending a single 64bit card as a NIC, for example.