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Thread ID: 81197	2007-07-20 00:52:00	VIA Apollo Pro, SiS 315, AGP 4x and Driving value. Confused? I am...	Agent_24 (57)	Press F1

Post ID	Timestamp	Content	User
570470	2007-07-20 00:52:00	Ok so here's how the story goes: The mouse and keyboard ports on my Asus CUSI-M died, forcing me to upgrade to something with an AGP slot, in this case an Aopen AX34 Pro. The mobo supports 1x - 4x AGP, and the SiS 315 card that i've got in there at the moment supports 2x - 4x AGP. Now I've got the card's jumper set to 4x, and I've had it working @ 4x fine in another PC before now, so I know it's all good. But once loaded windows, the SiS drivers tell me the mobo supports up to 4x but my card only supports 2x and is only running at that speed. I've got AGP 4x set and enabled in the BIOS (which I upgraded 4 years from the initial 1.0 release to the latest 1.17) There is also an option of changing the AGP 'Driving value' (which I have never heard of before) from values of DA - FF An archived version of viahardware.com on web archive suggests changing this value for better stability in games... but My question is this: What is this 'Driving Value'?, Will changing this allow me to run in full AGP 4x, and would it be possible to break anything by changing this value?	Agent_24 (57)
570471	2007-07-20 01:02:00	And after you replaced the mobo, did you install the mobo drivers for it?? And even tho x4 is enabled in the BIOS, is it set to AGP / not PCI if this is in the BIOS as well?	Speedy Gonzales (78)
570472	2007-07-20 01:04:00	he presence of the AGP Driving Control is specific to VIA chipsets, so if you have it, you have a VIA chipset (more on that later). The AGP Driving Control allows you to control, quite specifically, the AGP driver signal strength. Due to the design of the AGP protocol (which specifies the bus as well) this is directly related to timing. So, by selecting a manual hex range (00h-FFh) we are setting the timing of the signal that your video card's driver uses to communicate across the AGP bus. So an AGP Driving Value allows you to specify a concrete signal strength for your AGP driver. Hopefully, this will hopefully provide it with enough strength to remain stable, and function properly on your motherboard. To see an example of just how important this is, consider the large-die (and rather inefficient) GeForce 256, which had many motherboard compatibility issues. Many motherboards wouldn't even POST with a GeForce 256 in them (Athlon and Via combos, most commonly). This problem stemmed from to two main issues: under-rated power supply, and motherboards that didn't really supply the specified voltage to the video card. Provided you are getting enough power to the motherboard, your machine will POST, but a VIA chipset still isn't managing your GeForce 256 AGP card properly. So the 'Manual' AGP Driving Control setting is VIA's way of skirting chipset design and driver issues, by allowing them to configure for optimal scenarios. Before you decide that this sounds too harsh, keep in mind that today everyone optimizes for Intel everything and not much of VIA or AMD anything. So we might say this is for 'performance tuning', and we also might say this is for overall compatibility issues with VIA's AGP implementation. Note that the default for the AGP Driving control is going to be 'Auto'. This is pretty much akin to your 'auto' ram-timing selection; it is the lowest-common denominator settings that are going to yield you the widest compatibility at the cost of performance. Motherboard- and card-specific settings Since the "AGP Driving Control" BIOS option is specific to the VIA chipset's AGP implementation and there are multiple motherboards based on the VIA chipset, I would have to say that for certain motherboards there is no magic setting that works with every graphics card and motherboard combination. For instance, a setting of CCh on a particular motherboard is not going to mysteriously work better with every card than a setting of BAh. As for how to find out the specific settings recommended for various video cards, the best recommendation would be to contact your video card vendor first (and I would attempt to contact the chipset provider as well, if they are an IHV (like nVidia)). Ask them what their recommended manual timing is. Some motherboard vendors will recommend manual timings (for specific cards), but not to end users. They will usually only offer that type of support to VARs/Resellers. The only straight answer on manual timings that I have been able to get is from Epox and Tyan. For the original Geforce 256's, they recommend A8h for timing control. This is independent of driver, but dependant on chipset. With the Geforce 256 GTS they recommend a manual setting of BAh. Asus, keeping with PC tradition of doing your own thing, recommends a setting of B9h for their 6600 Pure card. Tyan used to recommend DCh with everything (as a few other vendors have posted on their websites), but with all Tyan VIA-chipset motherboard BIOS updates posted after 2/15/2000, you will notice they now recommend CCh. If I can gather the requisite information from the motherboard vendors (or even VIA, but not too likely) I will compile a cheat-sheet list of recommended AGP Driving Value codes. We'll revisit this topic then, but don't look for this quickly. My experience from the VAR side of the business, is that these people can take weeks and weeks to respond to an email. One more thing to keep in mind is that you're probably not going to need the AGP Driving Control feature if you are using AGP 1x or 2x, either. So if you are still using nVidia 3.x drivers, or any other non-AGP 4x compliant card/driver, you shouldn't worry too much about this. The feature is there mainly to accommodate the demands of AGP 4x, and [with nVidia] you can't even make use of it until 5.x and 6.x driver revisions (Detonator 2 and Detonator 3 series). Borrowed info	SolMiester (139)
570473	2007-07-20 01:13:00	And after you replaced the mobo, did you install the mobo drivers for it?? And even tho x4 is enabled in the BIOS, is it set to AGP / not PCI if this is in the BIOS as well? I did a full reinstall and installed the latest VIA 4-in-1 from viaarena.com and latest 315 driver from SiS I'll go check those other options and see..	Agent_24 (57)
570474	2007-07-20 01:34:00	Then find an application that will show a significant difference on 4x. AFAIK most game software was designed around 2x for compatibility reasons. Almost all of the gain in Vid card performance came from more onboard memory rather than AGP speed.	PaulD (232)
570475	2007-07-20 05:22:00	The mouse and keyboard ports on my Asus CUSI-M died, forcing me to upgrade to something with an AGP slot, in this case an Aopen AX34 Pro. Could have just used USB or one of those adpaters shown in the DSE link on another thread. I'd have kept an ASUS over an Aopen any day.	pctek (84)
570476	2007-07-20 05:35:00	Who knows what else would blow up on it though? the Aopen is faster and has a lot more features though, such as AGP which means I'm not stuck with pathetically useless SiS630E onboard "graphics" I know SiS315 isn't much of an upgrade but it beats the hell out of the SiS630E	Agent_24 (57)
570477	2007-07-20 06:26:00	nice post SolMiester ! :) i wouldn't worry about if it runs a agp 2x or not. the card isn't fast enough to warrant even 2x.	tweak'e (69)
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