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Adding more pci slots

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Reply 21 of 29, by wiretap

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I got the idea from a friend on another forum who linked me to his build log here: https://www.sweclockers.com/galleri/14409-via … retro-lan-dator

Here's some more pictures of my build:
https://imgur.com/gallery/vG6KVaH

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Reply 25 of 29, by darry

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wiretap wrote on 2021-01-22, 17:19:

All it is doing is provding a path for bus enumeration.
https://en.wikipedia.org/wiki/PCI_configurati … Bus_enumeration

Nice! I really did not expect a bridgeless extender to work (referencing also your later posts in this thread). Since you seem way more knowledgeable and experienced than I am on this subject, do you know

a) if the typical BIOS in a motherboard with PCI slots will typically properly enumerate and initialize devices in "extended" PCI slots on the primary PCI bus to allow functionality in pure DOS or is Windows/Linux required ?
b) if PCI devices that require an IRQ will work properly on such an extender ?
c) if electrical and or signal propagation delay constraints the only reasons why bridged solutions are used (in the context of legacy PCI expansion, if conversion between PCI/PCI-X and PCI Express is needed a bridge is obviously required ) ?
d) what is the maximum number of slots a single legacy PCI bus can have and how do "extended" PCI slots figure into this maximum ?

Reply 26 of 29, by Pierre32

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wiretap wrote on 2021-01-22, 21:01:

I got the idea from a friend on another forum who linked me to his build log here: https://www.sweclockers.com/galleri/14409-via … retro-lan-dator

Here's some more pictures of my build:
https://imgur.com/gallery/vG6KVaH

That's excellent 😀

Reply 27 of 29, by wiretap

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darry wrote on 2021-01-23, 01:29:
Nice! I really did not expect a bridgeless extender to work (referencing also your later posts in this thread). Since you seem w […]
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wiretap wrote on 2021-01-22, 17:19:

All it is doing is provding a path for bus enumeration.
https://en.wikipedia.org/wiki/PCI_configurati … Bus_enumeration

Nice! I really did not expect a bridgeless extender to work (referencing also your later posts in this thread). Since you seem way more knowledgeable and experienced than I am on this subject, do you know

a) if the typical BIOS in a motherboard with PCI slots will typically properly enumerate and initialize devices in "extended" PCI slots on the primary PCI bus to allow functionality in pure DOS or is Windows/Linux required ?
b) if PCI devices that require an IRQ will work properly on such an extender ?
c) if electrical and or signal propagation delay constraints the only reasons why bridged solutions are used (in the context of legacy PCI expansion, if conversion between PCI/PCI-X and PCI Express is needed a bridge is obviously required ) ?
d) what is the maximum number of slots a single legacy PCI bus can have and how do "extended" PCI slots figure into this maximum ?

(a) A device will work just as intended on the normal PCI slot.
(b) See (a)
(c) I don't quite know what the question is here, but these bridge/extender devices are normally used to conform to specific form factors. (i.e thin or desktop cases, ITX, 1U/2U servers, etc.)
(d) Per the PCI specificaiton, up to 256 buses, each with up to 32 devices, each supporting up to eight functions. I have some legacy rackmount servers at work that have 16 PCI slots in them (two 8-slot backplanes). With riser type cables that insert into one slot, you also have to take into account electrical power. If you try to drive too many devices off one slot, you can exceed the power rating of the slot and potentially damage the motherboard.

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Reply 28 of 29, by darry

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wiretap wrote on 2021-01-26, 17:32:
(a) A device will work just as intended on the normal PCI slot. (b) See (a) (c) I don't quite know what the question is here, bu […]
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darry wrote on 2021-01-23, 01:29:
Nice! I really did not expect a bridgeless extender to work (referencing also your later posts in this thread). Since you seem w […]
Show full quote
wiretap wrote on 2021-01-22, 17:19:

All it is doing is provding a path for bus enumeration.
https://en.wikipedia.org/wiki/PCI_configurati … Bus_enumeration

Nice! I really did not expect a bridgeless extender to work (referencing also your later posts in this thread). Since you seem way more knowledgeable and experienced than I am on this subject, do you know

a) if the typical BIOS in a motherboard with PCI slots will typically properly enumerate and initialize devices in "extended" PCI slots on the primary PCI bus to allow functionality in pure DOS or is Windows/Linux required ?
b) if PCI devices that require an IRQ will work properly on such an extender ?
c) if electrical and or signal propagation delay constraints the only reasons why bridged solutions are used (in the context of legacy PCI expansion, if conversion between PCI/PCI-X and PCI Express is needed a bridge is obviously required ) ?
d) what is the maximum number of slots a single legacy PCI bus can have and how do "extended" PCI slots figure into this maximum ?

(a) A device will work just as intended on the normal PCI slot.
(b) See (a)
(c) I don't quite know what the question is here, but these bridge/extender devices are normally used to conform to specific form factors. (i.e thin or desktop cases, ITX, 1U/2U servers, etc.)
(d) Per the PCI specificaiton, up to 256 buses, each with up to 32 devices, each supporting up to eight functions. I have some legacy rackmount servers at work that have 16 PCI slots in them (two 8-slot backplanes). With riser type cables that insert into one slot, you also have to take into account electrical power. If you try to drive too many devices off one slot, you can exceed the power rating of the slot and potentially damage the motherboard.

Thank you for answers and my resulting education . For question c), I was mainly wondering in what scenario(s) PCI-PCI bridges would be absolutely necessary since, if I understand correctly what you are saying, even an extender device could conceivably be made without using a bridge chip .

Reply 29 of 29, by The Serpent Rider

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For question c), I was mainly wondering in what scenario(s) PCI-PCI bridges would be absolutely necessary

PCI specs and electrical/chipset limit are two different things. Electrical limit is apparently 10 devices per one bus and chipset limit could be lower. And popular retro choices like 440BX just use PCI bus to connect north bridge and south bridge, so practically everything on SB is routed through PCI bus.

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