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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slewis5150 - Sunday, February 29, 2004 - link
How is this going to relate to pci eXpress?Pumpkinierre - Thursday, February 19, 2004 - link
So, Wesley#24, does this mean that some of the low maximum overclocks AT has shown for the A64 might have been as a result of PCI bus failure. Wouldnt it be possible to have a go at 234MHz for the Aopen and some of these other chipsets which supposedly had a PCI lock (nf3,SIS) but may be, like VIA, a dividor transition.Wesley Fink - Wednesday, February 18, 2004 - link
#23 - As we were testing in the article, none of the current Athlon64 chipsets have working PCI locks - and that includes nVidia and SiS (at least on the ECS). Some of the board makers do have a feature where a 1/7 multiplier kicks in at 233 and the PCI bus drops back to spec. We found that to be the case on the AOpen AK86-L which uses the VIA chipset.Jeff7181 - Wednesday, February 18, 2004 - link
Ummmm... I was pretty sure Sis and nVidia both had PCI/AGP locks and Via is the only one who can't get it right. Is this untrue?Xentropy - Tuesday, February 17, 2004 - link
Is this article going to be updated with the new information about 1/7 dividers and which boards have them? Not everyone reads the comments and would see the details.bigtoe33 - Tuesday, February 17, 2004 - link
Guys I bought the PCI geiger for Wesley from www.scan.co.uk They still show stock but I have just been informed its a discontinued product. If you want one I would grab one now.soki - Tuesday, February 17, 2004 - link
Good Job Wesley!Pumpkinierre - Monday, February 16, 2004 - link
Thank you Wesley!Wesley Fink - Monday, February 16, 2004 - link
As many have suggested as a possibility, it does appear different multipliers kick-in at 234 on the AOpen AK86-L. At a 233 setting PC Geiger shows PCI speed as 38.8, while at 234 the PCI readout drops to 33.2.TrogdorJW - Monday, February 16, 2004 - link
Is there any chance that a BIOS hack or something could adjust the PCI clock later in the boot process? You stated that you didn't load the OS and only booted into the BIOS. This seems a bit of a quick-and-dirty test, especially with the A-Open having acheived much higher results than other boards.My suggestion, in addition to including higher bus speeds, is to also get to the point where the OS is actually being loaded. You don't need to let it boot completely, but at least let it start. Get well beyond the BIOS POST test before assuming that the PCI speed being reported is "final".
On the other hand, the people questioning whether or not ALC655 and various other devices would run at 43 MHz... that's actually quite possible. Back in the day, I had a Pentium MMX 200 running at 250 on an A-Bit IT5H motherboard, which ended up being an 83 MHz bus and AGP and a 41.5 MHz PCI. (Ahhh... the good old Intel 430 HX chipset. Those were the days! /nostalgia.)
Later, I had Celeron 300A through 366 all running on 83.3 MHz bus, giving the same overclocked PCI and AGP. Finally, I am STILL running an A-bit BE6-II Rev. 2.0 motherboard on a 133 MHz bus. That motherboard has a 1/4 PCI divider, so PCI is in spec, but the AGP is running 2/3 and is at 88.9 MHz! I have a GeForce 4 MX 440 in it and it serves as my movie/music entertainment center.
Having been an overclocker since the days of the Pentium 166, I feel quite safe in saying that the "overclockability" of devices varies greatly. Some ATA/IDE setups can't handle more than 5 MHz out of spec (38 MHz or so), while others can clearly handle AGP and/or PCI speeds up to 33% out of spec. Only thorough testing will say for sure what any device can handle, and that's way beyond the ability for any one company/website to test.