PCIe to PCI and vice-versa adapters powermac compatibility?

[r34per]

I'm looking at some for an unrelated build, but it got me thinking whether they would work on powerpc macs as well. Specifically looking at the cheaper adapters like this one for, which looks to use the ASM1083 bridge chip to adapt pci to pcie. Would that work on something like a DC G5 to plug pci cards into?

And going the other way, a card like this, which uses a PXE8112 bridge chip, for adapting pcie to pci. Seems to need pci revision 2.3, are any pci powermacs it would work with?

I apologize if this has been asked already, but when I UTFSE'd it i couldn't find a definitive answer.

 

[DearthnVader]

In theory they should work, but some of these cheap PCI-E to PCI bridges can be buggy.

I recommend the "breakout" style cards as fitment issues can also be a bitch.

 

[joevt]

PCIe to PCI is normal. A PCIe to PCI bridge is used to connect some older PCI devices such as this example from my MacPro3,1 (the bridge is 2.5 GT/s x1, and of course the PCI device doesn't have a PCIe express link rate or width - maybe I should add PCI bits (16/32/64) and frequency (33,66/133,266/533 MHz) to the output of my pcitree.sh script):

│└┬1a:00.0-[1b]       # g1x1           [104c:823e] [0604]          PCI bridge                : Texas Instruments XIO2213A/B/XIO2221 PCI Express to PCI Bridge [Cheetah Express]
│ └─1b:00.0           #                [104c:823f] [0c00]          FireWire (IEEE 1394)      : Texas Instruments XIO2213A/B/XIO2221 IEEE-1394b OHCI Controller [Cheetah Express]

Here's another adapter:
https://www.amazon.com/StarTech-com-Express-Adapter-Card-PCI1PEX1/dp/B0037ECAM2?th=1

I don't know about PCI to PCIe. The PXE8112 is interesting because it works in either direction.
https://www.macrogroup.ru/sites/default/files/uploads/8112_pb_ec111207.pdf
https://www.cl.cam.ac.uk/~djm202/pdf/specifications/pcie/pci_express_bridge10.pdf
https://www.amazon.com/StarTech-com-Express-Adapter-Card-PCI1PEX1/dp/B0037ECAM2?th=1

In either case, find out how much height the adapter adds to the PCI(e) card and get a standoff that has the same height (if the adapter doesn't come with one). The following example uses 3/4 inch standoffs but you may need longer and hope the card doesn't have protrusions that interfere with the black plate of the computer:
https://forums.macrumors.com/threads/thunderbolt-3-m-2-nvme-ssd-enclosures.2027925/post-30814810

What about PCIe to AGP? Some graphics cards used a PCIe to AGP bridge. Is there a separate adapter for this purpose? One was announced but I don't know if you can buy it.
https://en.wikipedia.org/wiki/Accelerated_Graphics_Port#Later_use
https://hardforum.com/threads/agp-pcie-converter.1125237/
https://www.vogons.org/viewtopic.php?p=925776#p925776

 

[joevt]

Question about PCI to PCIe. How do you access config space address > 0x100 on a PCIe device downstream of a PCI root? PCIe supports 4K of config space ("Extended Configuration Space") but PCI only supports 256 bytes? The bridge spec defines the different types of transactions and "Enhanced Configuration" mechanisms but doesn't say how to initiate the transactions (which may differ from system to system?). Are there systems that can't do the Enhanced Configuration mechanisms? I'm just wondering if there are any PCIe cards that can't work in a PCI system. Maybe it works for PCI-X but not PCI ("PCI-X Mode 2" has 12 bit config space addresses). For example, can you add Thunderbolt to a PowerPC B&W Mac? Have to look at Apple Open Source code for PCI devices and bridges for PowerPC Mac OS X.

 

[LightBulbFun]

I have a Startech PCI to PCIe adapter I bought specficly to mess about with PCIe cards in PCI based macs

I can confirm it does indeed work and I got a PCIe SATA card to show up in a G4 QuickSilver, but I have not been able to test it futher yet

im hoping in time to be able to unearth my G5 Quad and see if the PCIe GeForce 6600 thats inside, will work with the PCI-PCIe adapter

(IE will OpenFirmware be able to load a PCIe cards option ROM through it?)

and if THAT works, then I want to get a X1900 GT and see if that works, and if that works, then I want to shove it into My G3 Beige or 9600 and see if I one can Finally get Core image going on an Old world ROM mac (assuming the X1900 GT's Option ROM is OWR friendly, generally ATI card Option ROMs are tho)

Startech also made a Nifty PCI-X to PCIe 4x bridge card that would be fun to play with (as it would make full use of the 64 bit slots in PowerMacs) but sadly they where discontinued a while back

 

[kocoman]

I have a Startech PCI to PCIe adapter I bought specficly to mess about with PCIe cards in PCI based macs

I can confirm it does indeed work and I got a PCIe SATA card to show up in a G4 QuickSilver, but I have not been able to test it futher yet

im hoping in time to be able to unearth my G5 Quad and see if the PCIe GeForce 6600 thats inside, will work with the PCI-PCIe adapter

(IE will OpenFirmware be able to load a PCIe cards option ROM through it?)

and if THAT works, then I want to get a X1900 GT and see if that works, and if that works, then I want to shove it into My G3 Beige or 9600 and see if I one can Finally get Core image going on an Old world ROM mac (assuming the X1900 GT's Option ROM is OWR friendly, generally ATI card Option ROMs are tho)

Startech also made a Nifty PCI-X to PCIe 4x bridge card that would be fun to play with (as it would make full use of the 64 bit slots in PowerMacs) but sadly they where discontinued a while back

what is the chip? is it PCI1PEX1 and the chip is Pericom - PI7C9X111SL, how it compare vs pxe8112
thx

 

[joevt]

I have a Startech PCI to PCIe adapter in my Power Mac 8600. I haven't really tried it yet - just confirming that it can see PCIe devices such as NVMe, XHCI or PCIe switch chip.

It's the PCI1PEX1 which uses the PI7C9X111SL 32bit 33MHz.

00:0f.0 PCI bridge [0604]: Pericom Semiconductor PI7C9X111SL PCIe-to-PCI Reversible Bridge [12d8:e111] (rev 02) (prog-if 00 [Normal decode])
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
    Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 32, Cache Line Size: 32 bytes
    Interrupt: pin A routed to IRQ 0
    Bus: primary=00, secondary=01, subordinate=05, sec-latency=0
    I/O behind bridge: 00001000-00000fff [disabled]
    Memory behind bridge: 88000000-880fffff [size=1M]
    Prefetchable memory behind bridge: 0000000088000000-0000000087ffffff [disabled]
    Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+ <SERR- <PERR-
    BridgeCtl: Parity- SERR- NoISA+ VGA- VGA16- MAbort- >Reset- FastB2B-
        PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
    Capabilities: [80] PCI-X bridge device
        Secondary Status: 64bit- 133MHz- SCD- USC- SCO- SRD- Freq=conv
        Status: Dev=ff:1f.0 64bit- 133MHz- SCD- USC- SCO- SRD-
        Upstream: Capacity=16 CommitmentLimit=16
        Downstream: Capacity=16 CommitmentLimit=16
    Capabilities: [a8] Subsystem: Device [0000:0000]
    Capabilities: [b0] Express (v1) PCI/PCI-X to PCI-Express Bridge (Slot+), MSI 00
        DevCap:    MaxPayload 128 bytes, PhantFunc 0
            ExtTag+ RBE-
        DevCtl:    CorrErr- NonFatalErr- FatalErr- UnsupReq-
            RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
            MaxPayload 128 bytes, MaxReadReq 512 bytes
        DevSta:    CorrErr- NonFatalErr- FatalErr- UnsupReq- AuxPwr+ TransPend+
        LnkCap:    Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit Latency L0s <512ns, L1 <1us
            ClockPM- Surprise- LLActRep+ BwNot- ASPMOptComp-
        LnkCtl:    ASPM Disabled; Disabled- CommClk-
            ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
        LnkSta:    Speed 2.5GT/s (ok), Width x1 (ok)
            TrErr- Train- SlotClk+ DLActive+ BWMgmt- ABWMgmt-
        SltCap:    AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug- Surprise-
            Slot #0, PowerLimit 0.000W; Interlock- NoCompl-
        SltCtl:    Enable: AttnBtn- PwrFlt- MRL- PresDet- CmdCplt- HPIrq- LinkChg-
            Control: AttnInd Unknown, PwrInd Unknown, Power- Interlock-
        SltSta:    Status: AttnBtn- PowerFlt- MRL- CmdCplt- PresDet- Interlock-
            Changed: MRL- PresDet- LinkState+
    Capabilities: [d8] Vital Product Data
        Not readable
    Capabilities: [f0] MSI: Enable- Count=1/1 Maskable- 64bit+
        Address: 0000000000000000  Data: 0000

There was some discussion of PCI or PCI-X to PCIe bridges at https://forums.macrumors.com/thread...l-work-in-a-beige-power-macintosh-g3.2303689/

Power Macs can support 32bit at 33 or 66MHz, 64bit at 33MHz (PCI), 64 bit at 100MHz or 133MHz (PCI-X) so you would want an adapter that supports your bus speed. The Startech PCIX1PEX4 uses the PEX8114 which should support all the bus speeds (25,33,50,66,100,133MHz) but I don't know if the StartTech supports all the modes that the PEX8114 allows. The manual says it doesn't support 66MHz. #704

 

[joevt]

or maybe the jumpers just set the max speed (33 or 133MHz) and it will negotiate lower speeds (100, 66, 33MHz) if necessary?