My brother noticed a few weeks ago that PCI and AGP buses on PC systems
don't really seem to be laid out as you would expect. An AGP slot is
supposed to be on a dedicated PCI bus in order to give the slot extra
bandwidth. However, comparing the output of `lspci -tv' (list PCI
devices, tree view, verbose) on different architectures makes me wonder
if PC systems have wandered down yet another poor design path.
As you can see from the output below, the different PCI buses on the
Sparc and Apple systems seem to have their own dedicated channels to the
chipset, while the AGP slot on my desktop appears to be attached through
the main PCI bus (don't get confused by the [02] bus -- that one really
is a card attached to the PCI bus that has it's own internal PCI-PCI
bridge for some reason). I suppose maybe the AGP slot really does have
dedicated pathways to the chipset, but things were just made to appear
this way for some reason.
Anyway, just another curiosity of the PC architecture, I suppose, but
does anyone have a reason why things might be laid out like this?
My Desktop (AMD Athlon):
-[00]-+-00.0 Advanced Micro Devices [AMD] AMD-760 [IGD4-1P] System Controller
+-01.0-[01]----05.0 Matrox Graphics, Inc. MGA G400 AGP
+-07.0 VIA Technologies, Inc. VT82C686 [Apollo Super South]
+-07.1 VIA Technologies, Inc. Bus Master IDE
+-07.2 VIA Technologies, Inc. USB
+-07.3 VIA Technologies, Inc. USB
+-07.4 VIA Technologies, Inc. VT82C686 [Apollo Super ACPI]
+-07.5 VIA Technologies, Inc. VT82C686 AC97 Audio Controller
+-08.0 QLogic Corp. QLA2100 64-bit Fibre Channel Adapter
+-09.0 Creative Labs SB Live! EMU10k1
+-09.1 Creative Labs SB Live! MIDI/Game Port
+-0a.0 Adaptec AIC-7860
+-0b.0 3Com Corporation 3c905 100BaseTX [Boomerang]
\-0c.0-[02]--+-00.0 NEC Corporation USB
+-00.1 NEC Corporation USB
+-00.2 NEC Corporation USB 2.0
\-01.0 VIA Technologies, Inc. IEEE 1394 Host Controller
Sun Ultra 30 (UltraSPARC) from work (no AGP, just two PCI buses):
-+-[01]-+-00.0 Sun Microsystems Computer Corp. Psycho PCI Bus Module
| +-01.0 LSI Logic / Symbios Logic (formerly NCR) 53c875
| \-01.1 LSI Logic / Symbios Logic (formerly NCR) 53c875
\-[00]-+-00.0 Sun Microsystems Computer Corp. Psycho PCI Bus Module
+-01.0 Sun Microsystems Computer Corp. EBUS
+-01.1 Sun Microsystems Computer Corp. Happy Meal
\-03.0 LSI Logic / Symbios Logic (formerly NCR) 53c875
My brother's Apple Powerbook (PowerPC):
-+-[24]-+-0b.0 Apple Computer Inc. UniNorth Internal PCI
| +-0e.0 Apple Computer Inc. UniNorth FireWire (rev ff)
| \-0f.0 Apple Computer Inc. UniNorth GMAC (Sun GEM) (rev 01)
+-[10]-+-0b.0 Apple Computer Inc. UniNorth PCI
| +-17.0 Apple Computer Inc. KeyLargo Mac I/O (rev 03)
| +-18.0 Apple Computer Inc. KeyLargo USB
| +-19.0 Apple Computer Inc. KeyLargo USB
| \-1a.0 Texas Instruments PCI1211
\-[00]-+-0b.0 Apple Computer Inc. UniNorth AGP
\-10.0 ATI Technologies Inc Rage Mobility M3 AGP 2x (rev 02)
--
_ _ _ _ _ ___ _ _ _ ___ _ _ __ Southern DOS: Y'all reckon?
/ \/ \(_)| ' // ._\ / - \(_)/ ./| ' /(__ (Yep/Nope)
\_||_/|_||_|_\\___/ \_-_/|_|\__\|_|_\ __)
[ Mike Hicks | http://umn.edu/~hick0088/ | mailto:hick0088 at tc.umn.edu ]
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