You shouldn't. Plain and simple.

There's an HD3870 that does crossfire on a single board, HD3870X2.

... or you could get two 3870X2 for extra silly crossfire action

They barely work as two cards in crossfire. Four cards are just horrible.

I have zero experience with 3870, but HD4870X2 has been in my daily driver for 5 years. Hot as hell and very noisy under load, but I haven't had any crossfire issues. The card just worked. I expected a little better performance with all the hype, but I got the card in 2014 for 40 euros, I don't think I get to be picky.

The ones I can buy is matched set of two HD3870 video cards, they are reference cards clear red housing, no heat pipe, all copper tall heatsink with bladed fan blower not standard blower commonly found. I already have cross fire bridges.

And did the driver develop with time as back then AMD/ATI drivers was shoddy?

PS: No to what, clarify please? (Referring to "The Serpent Rider", I noticed that he is kind of a flame bait style comments? This which I do not appreciate).

Cheers,

If they are cheap enough? Grab them, it'll be fun.

I've used 4870's and 6970's in x-fire and they were!

"Budget Builds - Official" on Youtube has reviewed most of the dual-GPU Radeon cards & included a lot of performance examples. He's also covered modding drivers for these cards to get better performance in modern games. Worth checking out if you want a quick look at how they do.

I never tried crossfire with it, but I had a pretty good experience with my old HD3850 AGP in a WinXP gaming box.

you can but... it often is going to give you trouble or no gain, and micro stutter
you can just buy a more powerful card, a HD4870 or something and it will be a lot better and it's less than a year newer,

if you are going for it, make sure the second PCIE slot is not one of those x4 connected to the southbridge that many boards had for cost saving and it was a poor fit for CF/SLI

HP Z420 is dual x16 slots due to 40 lanes of processor socket 2011.

Another option is use upper x16 @ x16 slot and open end x8 slot one place above the x16 slot.

There is no alternative PSUs as they come with 600W, hence the limitation on per card watts. Around 150W or less each will work. I use standard 8x 4GB 1Rx8 unbuffered ECC at DDR3-1866. I have adapters cables in storage to convert standard ATX PSU to HP spec. I need to design and make adapter plates. Gonna pre-test to learn what are needed to keep motherboard happy since HP designed office PC and workstations to sense and control many things.

Another way is use Z420 motherboard in a Z620 chassis to use 800W PSU but finding a shell with PSU is hard enough.

I ran Z230 workstation to use Z420 600W PSU, works well, plug and play by using a home made ATX CPU 12V from 8pin to 4pin (standard pinout) short cable adapter around 6cm long, but PSU fan spin full rpm. Need to figure out what what kind of signal PSU needs to bring down PSU's fan rpm to reasonable noise. It was not PWM as I had a PWM adjustable controller at both 15% cycle and 80% duty cycle (to simulate as inverted PWM if that in case also pre-set to 25KHz).

Cheers,

I used to run dual 4890's in CF back in the day and while performance was great at the time, I see little reason to put up with the downsides of CF (or SLI) these days. I would just go with a generation newer card which will get you equivalent performance without the multi-GPU pains. So unless you specifically want to go the CF route for the experience, then a 4870 will get you better performance, less issues and will probably also cost less. For the same reason I would also go with a single 3870 over dual 7900 geforces in SLI.

Intend to run at v-sync locked would that help with quality? Why others turn off the v-sync?

Cheers,

Intend to run at v-sync locked would that help with quality?

In best case scenario you would need to limit AFR Crossfire frame rate with vsync and other methods. Because AFR rendering doesn't work good when both chip are 100% loaded. In such situations, driver can't manage workload between multiple chips perfectly.

Why others turn off the v-sync?

1. Vsync creates noticeable lag (2-3 frames).
2. Slight screen tearing doesn't bother everyone.

Much better responses.

😀

I'm not intending to do it with much newer games, I'm matching the older games that supports dual GPU cards for games around 2000-2009 or so.

Thanks, keep coming guys!

Hardware Museum has some great videos. With charts that show you the frame rate stutters.

Radeon HD 3870 (3-way CF) vs GeForce 8800 GT (2-way SLI) - GPU Duel (ep. 20)
https://www.youtube.com/watch?v=iwnzl2XLI6g

GeForce 8800 GTX SLI vs Radeon HD 2900 XT CF - GPU Duel (ep. 15)
https://www.youtube.com/watch?v=XDEprAUdhpk

I think it's interesting to see and might be fun to try out, but yeah there are clear caveats to multi GPU that make it undesirable.

Crossfire used to have a mode called Supertiling that has considerable advantages over AFR, but it also required game support.

Crossfire used to have a mode called Supertiling that has considerable advantages over AFR

Supertiling is supported only by old hardware Crossfire, i.e. Radeon X850/1800/1900/1950 Crossfire edition cards.