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Comment by justsomehnguy | Hacker News Reader

> it was impossible to put more than a single AGP slot on a motherboard.

AGP is just PCI on steroids[0], so it's less than impossible and more like prohibitively expensive, because it would require an additional run to a dual-AGP-ported memory controller (which resided in the chipset in the times of AGP) which did not exist or additional system chipset, probably with it's own memory and all those SMP shenanigans from that.

BTW I think I heard about some motherboard which had two AGP slots, but the second one was AGP only physically/electrically, running over a standard PCI bus. But maybe my brain is just making things...

[0] https://www.youtube.com/watch?v=Pdl1Jwe9dcw

EDIT:

https://retrocomputing.stackexchange.com/questions/16863/was...

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> BTW I think I heard about some motherboard which had two AGP slots, but the second one was AGP only physically/electrically, running over a standard PCI bus. But maybe my brain is just making things...

I've not personally ever seen a board with dual AGP slots, but there were a number of AGP and PCI-e supporting oddballs during the transition period. I recall one of the more terrible ones doing something like basically just allowing an AGP card to hang off the PCI bus. There were some AGP/PCIe chipsets that were quite good during this time as well, but many of them seemed to be crappy hacks with performance limitations or compatibility problems.

Also interesting were the graphics cards that used Nvidia's AGP -> PCIe adapter chip which allowed them to keep selling older hardware on newer platforms.

https://www.asrock.com/mb/VIA/K7Upgrade-600/

It's not a real two slots, because you can use only one, of course.

AlphaServer ES47 and ES80 model has support for 4 and 8 AGP slots respectevly but that's cheating, they are server scalable systems. Maxed out GS1280 can support 16 AGP slots per partition.

They did test them with 4 cards, though.

https://www.hpe.com/psnow/doc/c04324523.pdf?jumpid=in_lit-ps...

https://docslib.org/doc/5603403/hp-alphaserver-es47-es80-gs1...

Unsurprisingly (in the context of the thread) some guy from Russia actually did AGP to PCI converter and it worked just fine (considering you can only use 3.3V cards on it):

https://www.youtube.com/watch?v=Jhp1_zBnAEk

> I recall one of the more terrible ones doing something like basically just allowing an AGP card to hang off the PCI bus

Intel 915 chipset:

https://www.anandtech.com/show/1344

Looks like this is what my mind mangled up to a dual AGP slot version.

Welp, guess there was no dual AGP consumer cards at all.

I did find a way to have two gfx chips on a single AGP card without glue logic. See my comment above in this thread.

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