At the same time I was thinking of what more I could do to pump the Quad up. Obviously the CPU is a dead-end, and I already have 8GB of RAM in it, which Tiger right now indicates I am only using 1.5GB of (with TenFourFox, Photoshop, Terminal, Texapp, BBEdit and a music player open) -- I'd have to replace all the 1GB sticks with 2GB sticks to max it out, and I'd probably see little if any benefit except maybe as file cache. So I left the memory alone; maybe I'll do it for giggles if G5 RAM gets really cheap.
However, I'd consolidated the USB and FireWire PCIe cards into a Sonnet combo card, so that freed up a slot and meant I could think about the video card. When I bought my Quad G5 new I dithered over the options: the 6600LE, 7800GT and 2-slot Quadro FX 4500, all NVIDIA. I prefer(red)
ATIAMD in general because of their long previous solid support for the classic Mac OS, but Apple only offered NVIDIA cards as BTO options at the time. The 6600LE's relatively anaemic throughput wasn't ever in the running, and the Quadro was incredibly expensive (like, 4x the cost!) for a marginal increase in performance in typical workloads, so I bought the 7800GT. Overall, it's been a good card; other than the fan failing on me once, it's been solid, and prices on G5-compatible 7800GTs are now dropping through the floor, making it a reasonably inexpensive upgrade for people still stuck on a 6600. (Another consideration is the aftermarket ATI X1900 GT, which is nearly as fast as the 7800GT.)
However, that also means that prices on other G5-compatible video cards are also dropping through the floor. Above the 7800GT are two options: the Quadro FX 4500, and various third-party hacked video cards, most notably the 2-slot 7800GTX. The GTX is flashed with a hacked Mac 7800GT ROM but keeps the core and memory clocks at the same high speed, yielding a chimera card that's anywhere between 15-30% faster than the Quadro. I bought one of these about a year and a half ago as a test, and while it was noticeably faster in certain tasks and mostly compatible, it had some severe glitchiness with older games and that was unacceptable to me (for example, No One Lives Forever had lots of flashing polygons and bad distortion). I also didn't like that it didn't come with a support extension to safely anchor it in the G5's card guide, leaving it to dangerously flex out of the card slot, so I pulled it and it's sitting in my junk box while I figure out what to do with it. Note that it uses a different power adapter cable than the 7800 or Quadro, so you'll need to make sure it's included if you want to try this card out, and if you dislike the lack of a card guide extension as much as I do you'll need a sacrificial card to steal one from.
Since then Quadro prices plummeted as well, so I picked up a working-pull used Apple OEM FX 4500 on eBay for about $130. The Quadro has 512MB of GDDR3 VRAM (same as the 7800GTX and double the 7800GT), two dual-link DVI ports and a faster core clock; although it also supports 3D glasses, something I found fascinating, it doesn't seem to work with LCD panels, so I can't evaluate that. Many things are not faster, but some things are: 1080p video playback is now much smoother because the Quadro can push more pixels, and high end games now run more reliably at higher resolutions as you would expect without the glitchiness I got in older titles with the 7800GTX. Indeed, returning to the BareFacts graph, the marginal performance improvement and the additional hardware rendering support is now at least for me worth $130 (I just picked up a spare for $80), it's a fully kitted and certified OEM card (no hacks!), and it uses the same power adapter cable as the 7800GT. One other side benefit is that, counterintuitively, the GPU is several degrees cooler (despite being bigger and beefier) and the fan is nearly inaudible, no doubt due to that huge honking heatsink.
It's not a big bump, but it's a step up, and I'm happy. I guess all that leaves is the RAM ...
In TenFourFox news, I'm done writing IonPower (phase 1). Phase 2 is compilation. That'll be some drudgery, but I think we're on target for release with 38ESR.