AGP

3 Articles

Why Some S3 Videocards Have A Brightness Issue

April 21, 2026 by 8 Comments

Once a pioneer in videocards, S3’s legacy is today mostly found in details like texture compression as well as the strong presence of S3-branded videocards in the retro-computing world. There’s however a bit of a funny issue with some of these S3 cards in what is often called a ‘brightness bug’, but which as [Bits und Bolts] covers in a recent video was actually a hardware feature that we can once again blame composite video for.

This issue appears with AGP cards like the Trio 3D, Trio64 and ViRGE, where the brightness on the output signal is set too high, easily seen with the washed out look on boot, where especially on CRTs you’d expect to see the nice deep black background. Using an S3 Trio 3D 2X card that was saved from the e-waste pile this so-called Pedestal Bit responsible is investigated and tweaked to show what difference it makes.

At the core is adjusting the black level to make scanline changes easier to detect for TVs, which is no longer relevant for CRTs, LCDs, etc., while adjusting the brightness for one videocard in a system can cause issues elsewhere, such as when using said card alongside a 3dfx Voodoo II card or with inconsistent brightness levels inside 3D games.

Fortunately S3 provided in-depth datasheets on their chips, including how to address the responsible bit. After demonstrating the principle, the BIOS is then patched to set this Pedestal Bit to the value of 0 on boot, solving the issue once and for all.

Continue reading “Why Some S3 Videocards Have A Brightness Issue” →

A Walk Down PC Video Card Memory Lane

September 28, 2025 by 30 Comments

These days, video cards are virtually supercomputers. When they aren’t driving your screen, they are decoding video, crunching physics models, or processing large-language model algorithms. But it wasn’t always like that. The old video cards were downright simple. Once PCs gained more sophisticated buses, video cards got a little better. But hardware acceleration on an old-fashioned VGA card would be unworthy of the cheapest burner phone at the big box store. Not to mention, the card is probably twice the size of the phone. [Bits and Bolts] has a look at several old cards, including a PCI version of the Tseng ET4000, state-of-the-art of the late 1990s.

You might think that’s a misprint. Most of the older Tseng boards were ISA, but apparently, there were some with the PCI bus or the older VESA local bus. Acceleration here typically meant dedicated hardware for handling BitBlt and, perhaps, a hardware cursor.

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A Better Use For The AGP Slot, Decades Later

March 3, 2024 by 25 Comments

For a while around a quarter century ago PC motherboards came with a special slot, a little shorter than the PCI slots which ruled the roost back then, and offset from them further into the case. This was the Accelerated Graphics Port, or AGP, a standard created to more quickly serve the 3D graphics cards which were then taking the world by storm. It was everywhere for a few years, then in the mid-2000s it was replaced by PCI Express and faded into obscurity. [Peter] has a Socket 7-based NAS with an AGP slot, and was left wondering whether the unused port could be put to a worthwhile purpose.

AGP is a superset of PCI clocked at 66 MHz, and usually benefiting from having its own exclusive bridge to the processor bus. Thus he reasoned that he could make an AGP to PCI adapter and it might work, as the right connections are all there. A hacked-together version was made by butchering two riser cards, and when a network card worked quite happily he knew he was on to something and made a PCB. There’s a caveat that it only works with 66-MHz capable PCI cards so not everything will work, but if you’re one of the very few people who must be in the market for one, he can do you a PCB.

We’d normally end with a link to a related project here, but we must instead congratulate [Peter]. As far as we can find, this is Hackaday’s first AGP hack, two decades later. Continue reading “A Better Use For The AGP Slot, Decades Later” →