Original URL: http://www.theregister.co.uk/2006/02/02/review_geforce_7800_gs_agp/

Nvidia GeForce 7800 GS AGP

One last gasp for AGP?

By Ryszard Sommefeldt

Posted in Hardware, 2nd February 2006 15:29 GMT

Review Hands-up who remembers AGP? Ah, just the two of you, thought as much. You'd be forgiven for thinking that'd be the way such a conversation with four million geeks would go, given all the coverage of PCI Express graphics cards and platforms since PCI Express became the kind of slot you'd most want to plug stuff into...

BFG GeForce 7800 GS OC

The reality is that AGP still sells well, even at the fairly high end, where ATI Radeon X800 and GeForce 6-series boards play. Indeed, Dixons here in the UK reports that they still ship 50:50 AGP:PCI-E when it comes to graphics boards, and 50 per cent of that first 50 per cent cost more than £100. So there's a bunch of you out there, to the tune of thousands of units a month, that want to drop decent money on AGP.

And for those with solid AGP systems that don't fall over and do exactly what you need them to do, why not? If it weren't for a VapoChill incident, there's a large chance that'd I'd be typing this to you from an AGP-based system that just rocked. Back when it still worked, anyway.

Sure, the latest and greatest would still have rolled my way, but I'm also a big proponent of not fixing what isn't broken. The ASUS SK8V is still one of my all time favourite mainboards, the Athlon FX-53 would still be very sweet today, and all I'd really be looking to upgrade would be the memory, to 2GB. Oh, and the graphics card.

You see, back then I was running an ATI Radeon 9800 Pro in my personal system. R350 kicked some ass back then, but it doesn't quite kick it now, especially with the likes of F.E.A.R. around. Folks running similar systems and still hanging on to a 9800 Pro or XT, or 5900 Ultra - cards that rip through Unreal Tournament 2004 at high-ish res - will be thinking the same.

If you're burning along with a card like that, you might be hankering after an upgrade right about now. There aren't many legs left to AGP, that much you have to admit. So, to get that copy of F.E.A.R. purring along using AGP, you're realistically looking at a Radeon X800 XL or GeForce 6800 GS, when it comes boards on sale today.

Today, yes, but in a week or so's time you'll also have the new GeForce 7800 GS AGP to pick.

Review by
Hexus.net

So what's under the hood? It'll no doubt surprise you to know that it's Nvidia's brand new 45nm test GPU, produced by ATI, codenamed RNV717 and clocked at 2000MHz. No, really, they're just marked as 'G70' to put you off the scent.

No, it's an A2 G70 cores that hasn't quite made the grade as a 7800 GT or GTX on PCI Express. Paired with Nvidia's BR2/HSI PCI Express-to-AGP bridge chip, the G70 gets to ride a very short PCI-E bus to school with AGP 8X compatibility on the far side.

GeForce 7800 GS AGP boards are specified with 256MB of GDDR 3 at 600MHz (1.2GHz effective), endowing the 375MHz GPU with gobs of memory bandwidth with which to get the job done. Texturing rate on mainstream GeForce 7-series products is limited by memory bandwidth, so the apparent excess shouldn't go to waste. There are 16 pixel pipelines.

Since it's powered by a G70, the GeForce 7800 GS AGP gets some excellent additions to image quality and potential performance per clock (and Watt), compared to 6-series products like 6800 GS.

The G70 allows for transparency anti-aliasing, a rendering ability that allows the GPU to essentially push alpha textures through the antialiasing hardware for extra Z or colour samples outside of what they'd usually get, at a sub-pixel level. The resulting extra data allows the chip to draw alpha textures at higher IQ than normal. The G70's texture cache gets tweaked for better access performance when filtering, so the hit for applying IQ enhancing texture filtering is less than 6-series hardware.

The G70 is also better at issuing scalar instructions in its vertex units - of which there are six in the 7800 GS AGP - which I guess to be down to auto-vectorisation tweaks. Triangle setup is appreciably quicker than 6-series per clock and it's well known that the fragment hardware in the G70 will do an NV35-esque double MADD issue per cycle, 4D wide.

In easy to understand terms, the G70 takes a poop on NV40, clock-for-clock, especially when it comes to pixel shading. So even moderately clocked there's a lot to be said for it.

Plenty of memory bandwidth keeps it all fed and the IQ improvements like gamma-correct antialiasing are all very welcome.

Unlocking the masked units and clocking it a bit are left as exercises for the reader. Fancy a peek at a retail board? BFG stood up to the plate, supplying us with its GeForce 7800 GS OC - and it's quite unlike any other GeForce 6 or 7-series board yet produced.

The first thing to notice - and it's a not an obvious change from other 6 or 7-series parts, AGP or otherwise - is that the analogue VGA connector is nearest the mainboard when installed, rather than at the top, for reasons we can't quite fathom. Trace routing around the chip-to-BR2 link is likely less fun that way, too.

BFG GeForce 7800 GS OC

Also notice the AGP connector and the four-pin Molex-style power connector, rather than the six-pin connector PCI Express boards use. You can see right through to the PCB if you look at the fan, indicating the GPU is elsewhere. The rear of the board says yes to that.

BFG GeForce 7800 GS OC

The recesses in the backplate tell you where the memory modules are and you can just about make out the (darker) traces running from AGP connector to somewhere under the backplate, letting you know the GPU is under there somewhere (but on the other side). Let's prove that.

BFG GeForce 7800 GS OC

BFG GeForce 7800 GS OC

Eight DRAM pieces make up the 256MB compliment the board has, and you can clearly see how the GPU is routed to the BR2 and then to the AGP connector. The bridge is actively cooled by the board's heatsink, just like the G70 GPU is. An example packaged during week 34 (near the end of August) in 2005, the A2 revision of G70 on the BFG GeForce 7800 GS OC s physically the same chip as that on a GTX or GT on PCI Express.

Being overclocked from the factory model, clocks on the BFG OC are 400/625, ahead of the reference clocks by 25MHz on both core and memory. Nvidia puts the peak current draw at just over 6A from +12V. Any PSU worth its salt today will handle that with ease.

While we've yet to run the BFG 7800 GS OC on our AGP reference platform, we have had the chance to run it on a decent AGP system:

Mainboard: Gigabyte GA-K8NNXP-940
Processor: AMD Athlon FX-53, Socket 940, 12 x 200
Memory: 2GB DDR400 Registered SDRAM, 200MHz, 3-3-3-8
Graphics Driver: NVIDIA ForceWare 83.40

BFG GeForce 7800 GS OC

Compared to the GeForce 6800 GS running on an nForce4 PCI Express system, with an AMD Athlon 64 FX-57 CPU, the BFG 7800 GS on AGP with FX-53 is ahead by over 80 per cent at 1280x1024 - the clocks and shader unit set-up see to that.

BFG GeForce 7800 GS OC

In Splinter Cell, the gains aren't as massive as they are with Quake 4, but more than 30% per cent extra performance is had at 1280x1024.

BFG GeForce 7800 GS OC

Compared to a recent test of a Radeon X1600 XT on PCI Express, with Athlon 64 4000+ (equal to our FX-53 in the AGP system), the BFG 7800 GS OC is ahead by over 50 per cent in our Far Cry benchmark.

While we're cross comparing to PCI Express systems with different CPUs and drivers, invalidating the numbers in a scientific sense, you can see the performance potential locked in to GeForce 7800 GS on AGP. It seems nicely ahead of anything readily available on AGP, brand new from retail.

Verdict

At a stated £229 including VAT and available almost immediately at your favourite retailer, the GeForce 7800 GS AGP looks like the best last-gasp option for AGP system users before they are forced into a jump to PCI Express.

While GeCube announced AGP-based Radeon X1600 boards recently and there are whispers of Sapphire doing the same, they've yet to hit retail or be announced by ATI in any formal fashion. They'll be the only brand new competition for 7800 GS from ATI, as the war on the AGP front draws to a close.

As the 7800 GS approaches the sub-£200 price point it almost becomes a mandatory purchase on AGP, based on performance numbers we've obtained with the BFG card so far. It beings enough extra performance and image quality to beat the 6800 GS as the best Nvidia AGP product you can get your hands on, and for the system I might have had I'd likely be picking one up today if I was buying brand new.

So the G70 powers another sales winner it appears, and the GeForce 7800 GS AGP seems like an attractive parts for those determined to stick with AGP. While PCI Express systems have large inherent platform benefits over even the best AGP-only systems - and it's really worth examining the switch if you can - this new AGP SKU will do the hangers-on just nicely.

Review by
Hexus.net