I never asked this, but is a 5770...

[soknar]

completely compatible with a 24-inch monitor at max resolution? I'm speaking of being able to maximize quality.

 

[sayantan]

A big no no....you might face problems in heavy weight games like crysis,mw2,gta4etc at max res and highest settings(including 8x AA)...I would recommend a 5870 for gaming at such resolution

 

[mohsentux]

and a 5870 is a little unaffordable for some people.listen if you've got the cash then buy a 5870 but since you've asked for 5700 series i'm geussing not.
listen why won't you do this (if you're mainboard can crossfire) buy a 5750 for now and stick to it for a while and when you could afford another one buy another and crossfire them.i wanna do this my self then i'll have a 2gb 256bit graphic card it's even better than a 5870
price for a 5870 is about 370 $
and price for a 5750 is about 120 $ (120*2 = 240)

 

[4745454b]

Except it doesn't work that way. Because everything is duplicated in CF, you end up with a card that is 2x 1GB 128Bit. You don't get a 2GB 256bit card.

As Sayantan said will have problems gaming on that card at that resolution. If you don't game or are willing to turn some details down you'll be fine. You should also consider the 5850 which handles itself quite well and is only $300ish.

 

[jyjjy]

Buying an HD5750 isn't a good call call for 1920x1080 even if you plan on crossfiring in the future because it's pretty weak for that resolution. The HD5770 is a better choice as it is a pretty good card for that resolution however and two in crossfire would be great, similar to an HD5870 even with the memory issue 4745454b mentions;
http://www.xbitlabs.com/articles/video/display/radeon-hd5770-hd5750-crossfirex.html
If you can afford it an HD5850 would be optimal however as it OCs to near the performance of an HD5870 anyway.

 

[mactronix]

Just to say that when 4745454b say's 2x 1GB 128Bit. Thats not the same as 2GB 128 bit.
Just thought i would mention it in case
Although i must admit when put like that i do have to question the assertion. Im no expert but wouldnt you get a 1GB 256 bit ish card ?
My logic here is that you do have 2 physical 128 bit feeds but as the info in memory is duplicated in the second card the Ram amount dosent actually go up.
So why dont you end up with a multiplication of the bandwidth ? because if you dont get a boost in either bandwidth or ram then whats teh point of dual cards.
Its been a very long day (28 hours) and i could be missing something really obvious here but please do tell.

Mactronix

 

[mohsentux]

yeah 4745454b are you saying if i crossfire 1gb 128-bit gpu i won't have a 2gb 256-bit ? why is that?it should duplicate everything please tell ASAP because in my country it's midnight now and i'm getting tired

 

[4745454b]

Why would it? You didn't double the number of traces going to and from the memory, you simply doubled the number of cards. You have 2 times everything, not double.

 

[soknar]

I'm extremely interested in the 5850 at the moment. I'm like a hair's length away from ordering one along with a corsair 850w psu to allow myself the ability for a full system upgrade in the future. However, I haven't a clue which brand is a good choice. I see sapphire, xfx, etc...

 

[mactronix]

Why would it? You didn't double the number of traces going to and from the memory, you simply doubled the number of cards. You have 2 times everything, not double.

@ mohsentux,
The memory dosent change because both cards need to know what the other is doing so each card has a copy of the same data which means you get no increase in actual Ram.

@4745454b,
Sure the memory side of things isnt changed but you have two cards outputting now so why dont you have what ever the scaling is giving you extra in bandwidth ? and in laymans terms that would mean say a 200bit bus. No ?

@ mohsentux,
Scalling if you dont know is basically the name for the amount of increase you get from a second card, you wouldnt get 100%.

Mactronix

 

[mohsentux]

oh no maaaan.i'm gonna show my brother trying to trick me can have consequences.

 

[jyjjy]

Although i must admit when put like that i do have to question the assertion. Im no expert but wouldnt you get a 1GB 256 bit ish card ?
My logic here is that you do have 2 physical 128 bit feeds but as the info in memory is duplicated in the second card the Ram amount dosent actually go up.
So why dont you end up with a multiplication of the bandwidth ? because if you dont get a boost in either bandwidth or ram then whats teh point of dual cards.

To work in tandem the two cards both need the same information in their individual ram so you aren't ending up with 2gb at 256 bit. They just act as one card with the same memory amount/bandwidth as is on each card to begin with. The increase in performance due to crossfire doesn't come from the memory it comes from being able to divide the processing load between the GPUs on each card.

 

[OvrClkr]

completely compatible with a 24-inch monitor at max resolution? I'm speaking of being able to maximize quality.

It depends, most games will require a more beefy card at that resoultion. A 5850 or dual 5770's should do the trick

A 4890 should be enough as well at that resolution but it all comes down to what games you play....

 

[mactronix]

To work in tandem the two cards both need the same information in their individual ram so you aren't ending up with 2gb at 256 bit. They just act as one card with the same memory amount/bandwidth as is on each card to begin with. The increase in performance due to crossfire doesn't come from the memory it comes from being able to divide the processing load between the GPUs on each card.

I may be getting my terminology mixed up here but the two cards are faster right? usually yes?
So they must be putting frames out faster ? So the fillrates are higher ? so the bandwidth must be higher as far as teh actual accumilater bandwidth that is being sent is concerned ? No.
It cant just be sending the info faster but the bandwidth be the same thats just plain nuts.

Mactronix

 

[mpavao81]

the 5850 would be a great choice, and would fit your needs nicely. As to what brand to get. Almost all of the brands are pretty good. My choices would be Sapphire/XFX/ HIS/

 

[4745454b]

We are getting to the point of where my knowledge starts to lack, so I'll take my best shot. For starters, look at this review of the 8800GS.

http://en.expreview.com/2008/01/29/review-galaxy-8800gs-384mb/236.html/2

Scroll down to where they are talking about the memory. Its missing to ram chips as compared to the 8800GT.

Take off the cooler and you can see the PCB is like Galaxy 8800GT, except it lacks two memory chips.

Ok, so the 8800GS has a 192bit bus while the 8800GT has a 256bit bus. 6ram chips divided by 192 = 32bits per chip, 8 ram chips divided by 256 = 32bits per chip. This means Nvidia is using 32bits per ram chip on these cards. My pure guess would be 16 traces leading to each ram chip, transferring 2 bits per clock.

To double the memory bandwidth you'd have to physically change the cards. You could increase the number of traces to each chip, or the number of chips, etc. By adding another card you are simply adding another card. You haven't actually changed anything physically on the card. It is not like adding another stick of ram and you went from 2GBs to 4GBs, or adding another harddrive and you now have an 500GBs in your system. Its a bit like adding a second monitor in clone mode. You now have two screens, 2x 1680x1050. You don't have 3360x2100.

 

[jyjjy]

I may be getting my terminology mixed up here but the two cards are faster right? usually yes?
So they must be putting frames out faster ? So the fillrates are higher ? so the bandwidth must be higher as far as teh actual accumilater bandwidth that is being sent is concerned ? No.
It cant just be sending the info faster but the bandwidth be the same thats just plain nuts. Mactronix

Well yes, operating at a higher level ideally could use more bandwidth. The improvements from crossfire are achieved despite the lack of bandwidth. This is reflected in that article I linked earlier in that while two HD5770s in crossfire average higher fps than an HD5870 the minimum fps are often are hurt in comparison. Occasionally the cards can't keep up because the memory subsystem is limiting the crossfired processors from performing at the high level they should.

 

[mactronix]

Well yes, operating at a higher level ideally could use more bandwidth. The improvements from crossfire are achieved despite the lack of bandwidth. This is reflected in that article I linked earlier in that while two HD5770s in crossfire average higher fps than an HD5870 the minimum fps are often are hurt in comparison. Occasionally the cards can't keep up because the memory subsystem is limiting the crossfired processors from performing at the high level they should.

Ok i get that but lets have on elast stab here. A 4870 has X memory bandwidth so wht does a 4870x2 list Xx2 as its memory bandwidth if a 4870x2 is basically 24870s crossfired on one board ?
I probably sound stupid but i cant for the life of me get my head around how its physically possable to get a higher performance without a higher total bandwidth.
Im going to bed with my headache soon

Mactronix

 

[4745454b]

The answer might be in my monitor example. I think the answer is that card0 can't use the bandwidth found on card1. It doesn't have access to it. Card0 only has access to whats on card0. Again, you have two times everything. Not double.

 

[sabot00]

Ok i get that but lets have on elast stab here. A 4870 has X memory bandwidth so wht does a 4870x2 list Xx2 as its memory bandwidth if a 4870x2 is basically 24870s crossfired on one board ?
I probably sound stupid but i cant for the life of me get my head around how its physically possable to get a higher performance without a higher total bandwidth.
Im going to bed with my headache soon

Mactronix

Depends what bandwidth you're talking about, if talking about CPU/Northbridge to graphics card, then it's very possible, you get more performance out of a 4870 than a 4850 but they both use PCI-E 2.0 & 16 lanes.

 

[jyjjy]

Ok i get that but lets have on elast stab here. A 4870 has X memory bandwidth so wht does a 4870x2 list Xx2 as its memory bandwidth if a 4870x2 is basically 24870s crossfired on one board ?
I probably sound stupid but i cant for the life of me get my head around how its physically possable to get a higher performance without a higher total bandwidth.
Im going to bed with my headache soon

Mactronix

Yes, the HD4870x2 has the same effective memory bandwidth as a single HD4870. It's not really that hard to understand. It would only make sense that performance wouldn't increase in crossfire if the memory subsystem is a severe bottleneck to begin with and it usually isn't.

 

[4745454b]

It has to be a little bit jyjjy. The specs of the 4850 and 4870 are almost the same. But the 4850 comes with DDR3 memory while the 4870 gets DDR5. The biggest differences are clock speeds and memory bandwidth. I could be wrong, but I don't think the 4850 is that close to the 4870 is it?

 

[jyjjy]

The HD4870 is in general 20-25% faster than an HD4850. It's also clocked 20% higher. At higher resolutions it tends to be closer to the 25% better so I guess that's the higher bandwidth due to DDR5 coming into play.

 

[mactronix]

Hang on how did we get a 4850 in there?
I have looked on various sites and a 4870 X2 has double the theoretical bandwidth that a single 4870 has. It has to it has 2 of every thing right ?
Now in the case of a X2 card you have 2 chips putting out twice the bandwidth because it has twice the traces. On a 4850 X2 for example its 512 listed as 256x2 so that means the board has the traces for 256 coming from each chip.
So why dosent it work the same with a more traditional multi card set up ?
I mean the traces come out of each card and go where exactly ? they meet up and become a collective do they not, and that collective is in effect the total bandwidth both cards are putting out ?
If this is not what happens then please tell me what does.

Im sorry to be a pain and i hope at least one of you understands where im coming from with this.
Thanks for your time and patience

Mactronix

 

[jyjjy]

You are incorrect. Like I said the HD4870x2 has the same effective memory bandwidth as a single HD4870. Both processors in the card have their own ram and it's own memory bus connecting to it that is 256-bits wide. So yes, they have 2 of everything, just like when you crossfire regular cards. The memory bus is relevant on the card only, it is the pathway between the processor and the onboard ram. Communication between the card and the rest of the computer is through the PCI-E x16 port and THAT is what is shared by the two processors on an HD4870x2