Standard Def Steve wrote:

However the 1440p slowdown only occurred in XP. Win7 was just fine, even with desktop composition disabled. So it may not have been an nForce4 issue, but rather an unoptimized WinXP driver for the GTX 560 I was using. But then again, those old VIA chipsets that are sluggish under XP run just fine under Win7 and 10, so who really knows what's going on there.

Something related to XP GDI acceleration perhaps. Also, 2560x1440 might be outside the range of some buffers of the era. Who knows. Something like how the X850 and 6800 cards were designed for 2 megapixel resolutions in 3D and if you went beyond that you lost efficiency because there were too many pixels for the occlusion culling buffers to completely manage.

ATI actually had some D3D10 GPUs that they didn't bother to support XP GDI acceleration at all with. At least for some number of drivers. I discovered this when I was running a 780G system and using the IGP. XP was horribly slow with any kind of redraw.

swaaye wrote:

Something related to XP GDI acceleration perhaps. Also, 2560x1440 might be outside the range of some buffers of the era.

That's what I'm beginning to think, as it's either fast (1080p or lower) or slow (1440p). Unlike those VIA chipsets, there's no in between. I also just slotted the GTX-560 into a much newer H77 motherboard, and found that XP at 1440p was slow on that machine, too. So I was wrong to blame the nForce4.

Interestingly, a GTX-680 does just fine with XP at high resolution.

Standard Def Steve wrote:

That's what I'm beginning to think, as it's either fast (1080p or lower) or slow (1440p). Unlike those VIA chipsets, there's no in between. I also just slotted the GTX-560 into a much newer H77 motherboard, and found that XP at 1440p was slow on that machine, too. So I was wrong to blame the nForce4.

Interestingly, a GTX-680 does just fine with XP at high resolution.

I have bad news. I don't know why it didn't dawn on me before, but I too have been playing with a 1440p monitor. I've been messing with various older PCIe cards with XP, 7 and 10. I am currently using a Z68 motherboard, though I have also used a nForce4 board. I threw in the GTX 580 that I have and it works fine with XP at 1440p. I actually don't recall any problems with 1440p and XP. I have also tried X1950, HD 2900 and GF 8800.

The Radeon X1000 series is pretty interesting. Dual link DVI (at least on the high-end cards). They do excellent 16-bit color dithering for old games. It looks better than what GF7 does. The X1000 cards just do better quality 3D in general than GF7. Work well with DGVoodoo1. No Windows 8/10 support though.

Huh. That is so weird. I wonder if the video BIOS (Zotac) has anything to do with this card's subpar QHD performance in XP. But yeah, it is exactly the same type of sluggishness I used to see with VIA chipsets back in the day. Even YouTube video is kinda choppy with XP @ 1440, with lots of tearing. It's as smooth as silk under 7, with or without desktop composition.

I can rule drivers out; I use the same XP driver with my GTX-680 and it's fine.

Yeah seems like it could be specific to that particular card.