PCI Speed and Overclocking: A Closer Look at A64 and P4 Chipsets
by Wesley Fink on February 16, 2004 9:42 AM EST- Posted in
- CPUs
PCI Speed and Overclocking: Test Configuration
One of the nice things about the PC Geiger is that PCI speed is displayed as soon as boot begins. To check the PCI speed, any PCI card polling and disabling was turned off in BIOS. We monitored the PC Geiger reported PCI speed at the beginning of boot and as we entered the BIOS screen. We did not boot into an OS.| Athlon64 FX51 Performance Test Configuration | |
| Processor(s): | Intel Pentium 4 3.2C AMD Athlon64 3200+ |
| Operating System(s): | N/A |
| RAM: | 2 x 512Mb OCZ 3500 Platinum Ltd 2 x 512Mb Mushkin PC3500 Level II |
| Hard Drive(s): | Seagate 120GB 7200 RPM (8MB Buffer) |
| Video AGP & IDE Bus Master Drivers: | N/A |
| Video Card(s): | ATI Radeon 9800 PRO 128MB (AGP 8X) |
| Video Drivers: | N/A |
| Motherboards: | Asus P4C800-E (Intel 875p) Asus P4S800D-E (SiS 655TX) Soltek SL-PT880PRO (VIA PT880) AOpen AK86-L (VIA K8T800) ECS 755A2 (SiS 755) Soyo CK8 Dragon Plus (nForce3-150) |
The motherboards tested were those available in our lab, but they were also selected to test the availability of PCI lock on various chipsets. The new VIA PT880 chipset claims a PCI lock and the Soltek SL-PT880PRO is the first production PT880 board that we have received. We were very impressed with the AOpen AK86-L for A64, which is the first VIA K8T800 board to show a working PCI/AGP lock in BIOS. The SiS 755 also showed a working PCI/AGP lock on the Reference Board, and the ECS is the first production SiS 755 board that we have received. The Soyo CK8 Dragon is a nForce3-150 board, and all the nF3 boards have claimed working PCI/AGP locks in their BIOS'.
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PrinceGaz - Monday, February 16, 2004 - link
I'm still awaiting any sort of reponse to the first post in this thread about why no tests seem to have been done at around 233 or 234FSB to see if a 1/7 divider kicks in. Thats the first thing I'd have tried after establishing no PCI lock at say 210 or 220. And yes, you can lower the multiplier on A64 chips so they aren't an issue like I said.Pumpkinierre - Monday, February 16, 2004 - link
Yes I second ionpro2's #13 suggestion. If you can get higher clockspeed by lowering the multiplier. try your geiger at these higher speeds and see what's going on.Icewind - Monday, February 16, 2004 - link
Now im curious as well as how you got it that highionpro2 - Monday, February 16, 2004 - link
Wesley Fink: No way that the motherboard would've posted with no PCI lock. Think about it: the devices that are dangling off of the PCI bus on the board itself would be running *way* the heck out of specification at the overclocks achieved on the Aopen. Perhaps these have higher tolerences, but I seriously doubt the ALC655 would run at 43Mhz, or the Realtek Gigabit LAN chip, either. Most likely, there are merely windowed dividers for these chips, with a 1/6 and 1/7 ratio. It would make sense for this to kick in at 220Mhz -- otherwise, you are running the PCI out of spec almost 10% down; and I'd be willing to bet whatever optimization is done for aftermarket cards is done for higher PCI/AGP speeds, not lower. *Please* test the AOpen board at 9x240 and see what PCI speed is reported.Wesley Fink - Monday, February 16, 2004 - link
Pumpkinierre -Your question is exactly the reason I stated that I don't know what is happening with AGP on A64 boards. With no PCI cards in my test setup, a working AGP lock could provide quite a bit of OC room. Some sites have reported AGP IS fixed on VIA, but I have no way of testing that. I can tell you for a fact that the PCI slots are not frequency locked on the A64 boards I tested, but the way frequencies are derived in HT it IS possible AGP is locked on some A64 boards.
Pumpkinierre - Monday, February 16, 2004 - link
I dont understand. You got 253MHzx8 and 240x9 on the Aopen A64 mobo when you tested it. That's a lot more than 220MHz. Even if the AGP was asynchronous, which I very much doubt, surely other components on the M'board would have seized?!impar - Monday, February 16, 2004 - link
I would like to see the same test in nForce2 boards...Icewind - Monday, February 16, 2004 - link
Sorry, guess I missed the defination of "go pound salt" so i'll take it with a grain of salt.idgaf13 - Monday, February 16, 2004 - link
If all The motherboard chipset suppliersdo the same thing ,such as the PCI lock,
musi be a "deeper"reasoning.
Certainly if possible ,contractually or technically, they would do it.
They all need that special selling point ,A point of differintation.
Basically "go pound salt" ,Icewind.
Icewind - Monday, February 16, 2004 - link
Cause VIA knows better and they still won't comply with the wishes of system builders. For that, I dispute them.