"The standard bios that came with the machine [emonster700k] is just not adjustable. After I ran a couple of tests I was able to enable "super bypass." Its somewhat of an urban myth in the Athlon community. Very few motherboards had the correct chipset stepping that enable the 5 - 15% performance enhancement. I used a program called chipid to enable it."

Super Bypass

Christmas came late for owners of Slot A Athlon systems when, four days after Chrismas day, Tom Pabst dusted the turkey and mayonnaise off his keyboard and posted this article on Super Bypass. He claimed a theoretical performance gain of up to 25% in Windows '98 and NT for cpu-memory transfers with one simple command to the AMD 751 Northbridge. Now this command set was built into the Northbridge set from day one, so what was the sudden spark of interest. Well, AMD had disabled the Super Bypass feature in early revisions of the 751 chipset, as it was technically fucked. But from revision C, stepping 5 and later the 751 chipset had a nice new feature, or bug fix, for extra performance.

What is it?

Super Bypass is a set of internal instructions for the 751 Northbridge that when enabled lowers the latency for transfers between the processor and memory by 25%. With a nice wide 200 MHz bus anyway, a lower latency should mean lots of extra performance, as this cpu-memory bus is one of the bottlenecks in very high speed systems, esp. Athlon ones.

Have I got it?

Use this utility to check if your board is Super Bypass capable or not. You must have a Revision C stepping 5 or better chipset to enable Super Bypass. Simply extract and run the prog in a DOS window. It does not run under Windows NT. An NT version is on the way.

How do I enable it?

Most of the newer BIOS's released now support it automatically if the chipset is capable. Asus K7M BIOS 1209 and later add automatic support for 751 revision C stepping 5 and over chipsets. MSI, Freeway, Gigabyte and others now have BIOS files that support Super Bypass.

My BIOS doesn't support it, my chipset does

You can use the chipID program to turn Super Bypass on and off from your autoexec.bat file. Extract it to your root directory, and add the line

• chipid/b+

and that's it. This will work on stepping 6 and over, probably work on stepping 5 and over and very possibly work on stepping 4 and over. According to AMD only stepping 5 and over chipsets support this feature properly, but some people report that if you set all BIOS values to default, esp. the memory timings, you can get it to work under DOS, and occasionally under Windows with stepping 4 chipsets. Lowering the BIOS memory timings does of course have the opposite effect on performance tho', so I wouldn't recommend it.

I want it now

The theoretical performance gain of 25% is for memory transfers across the cpu-memory bus only. This only translates as a performance increase for memory intensive applications and games. If the application is not using a large chunks of data dynamically streaming information in and out of RAM continuously and performing multiple calculations on it, but is just using a chunk of data without moving or changing it there will be very little, if any performance increase. Most available benchmarks give a 5-7% increase in memory bandwidth, and a smaller increase for other benchmarks.

Conclusion

It is a nice feature if you have it, but it's not worth fretting over if you don't have it. I'd recommend you make sure your next Athlon board supports Super Bypass, PC133 and AGP x4 and you'll be happy. Using the soft overclocking features of the K7M, and adjusting your memory timings to optimum will get you the same performance gain anyway. Check out the K7M Guide, and make sure you're running as well as you can.

Hard Drive "Upgrade"

03.28.03

I discovered that my eMonster 700k is capable of Ultra DMA 66. eMachines did not install an 80 conductor cable (probably since the original drive did not support it). I had updated the internal drive and did not realize the system was giving an error message behind the splash screen. Installed the 80 conductor cable that came with the drive and now I have no error.

Doug