The latest announcement from AMD is the new Athlon, claimed to be the most powerful processor ever for the x86 market. But this article is about the almost-latest of AMD’s processors, the K6-3. It has some features that are unique and not available in any other processor. Its biggest claim to fame is that it works in all recent Socket-7 motherboards. Socket 7 is the technology started by the Pentium processor when it first came out. You won’t see much of the Pentiums on the market, but they’re still manufactured and available today at very low cost. Most of what you can find on the market are Celerons, the Pentium II and III (in the Intel world anyway).

The K6-3 is supposed to be the successor to the K6-2, but both are being manufactured today, with the cost differential being more than $150. The K6-3 is available in 400 and 450MHz versions, with 475 and 500MHz versions coming soon.

Warning - Geek paragraph ahead. If it hurts your brain, skip this, and go to the next paragraph: The K6-3 is unique in that the processor contains a large second level cache memory (in addition to the first level cache) ON the chip. There are two 32KB level one caches, and then a built-in second-level 256K cache. AND it supports up to 2MB external cache on the motherboard. The Pentium II and III have two 32KB caches only; but the Celeron has two 32KB, plus a 128K L2 cache on the processor board, running at half the clock speed.

Cache is simply very fast memory. It is essential to running the processors at speeds so very much higher (up to 5.5 times) than the main bus speed. So the cache acts as a "bucket" for data, because the processor pushes it out faster than the bus can handle. The idea is that the processor, being so powerful, can spend its time predicting what it’s going to be asked to do next, and then doing it, in hopes that when the bus asks for it, the data will already be there. And this is a very successful way to do it. So it may follow that the bigger the memory cache is, and the more successful you are at predicting, the faster the computer will be.

There’s more to it than this. If you’re interested in learning more, I’d suggest going to http://www.mkdata.dk/click.

So to experience first hand what the K6-3 is all about, I built one a few days ago. I’m using it daily, and I have just a few observations to make about speed. But first, back to cache, sorry. Besides the Level 1 and 2 cache, the processor will support up to 2MB of Level 3 cache. Now with the K6-2 and Pentium II and III, that memory would have been called Level 2, because there are only two, one set on the chip and one on the motherboard. The Celerons all seem to have one set on the chip and one on the processor module.

So for a motherboard designed for the K6-2, when you put a K6-3 on it, it actually makes three caches available. I was able to find a motherboard with 2MB of onboard cache. It’s an interesting board in that it has no ISA slots and no slots for SIMMs. Just one AGP video and six PCI slots. That’s OK; there’s nothing in ISA that I can’t get (or already own in this case) in PCI. It’s an ATX configuration (as opposed to the older Baby-AT form).

ATX boards must have a different case. It’s usually about 1" wider; most are a couple of inches taller than a typical Mid-size AT case and two inches deeper. ATX boards are taller, narrower, and they use a different (and easier to plug in) power connector. And all the external connectors are made right on the board, so that they extend out the back of the case: keyboard, mouse, USB, serial and parallel connectors.

So this was pretty easy to put together because the ATX case is so large and has plenty of interior room. I did have one major problem though. Usually when I build a new machine, I set it up on my bench before actually putting it in the case. This is just to resolve any issues with the board, and it usually pays off because you have to get settings right on the board – moving jumpers around - and doing that outside of the case is easier than after it’s inside. But this time I did not because I don’t have a bench power supply with ATX connectors on it, and because I was in a hurry to go sailing that evening. And wouldn’t you figure, I powered it up, and everything is dead. No beeps, nothing on the screen, just nothing. But I do have a little diagnostic card I can plug in and detect fundamental problems. But NO! The card plugs into an ISA slot! I don’t have any!

So I did 45 minutes of dismantling all my work one piece at a time to see if I had a bad component plugged in, and substituting some things I had lying around and still I had a dead system. So I left to pick up some things and came back with a fresh mind, remembering that I hadn’t pulled all the small wires off the board that do things like power the LEDs on the front and the reset button and the power-up switch. So I just yanked them all off except for the power switch and … it worked! So I put it all back together and got the system running all OK. So finally I started putting the little wires back on and discovered that the thing that made it fail was the reset switch. The case manufacturer had wired it wrong so that it was normally closed instead of open. It was like you stood there with your finger on the reset switch all the time!

Fast ! Don’t ask me why, but I now own an AMD K6-2/400, a K6-2/300, and my server is an older IBM PR166+, and now I have this new AMD K6-3/450! I was of the opinion that you had to double the speed of a system for a subjective comparison, that with anything less than that you wouldn’t notice enough of a difference. So my expectations weren’t real high that I’d see the difference, but I’m very happy to report that it’s (subjectively) faster than anything I’ve used, including Pentuim II 500’s. AMD’s published benchmarks bear this out, but, after all, it’s they who are publishing the numbers. Even their own benchmarks show that the floating point speeds do not equal any comparable Pentium. And other benchmarks I’ve seen show a higher disparity – for floating point. But for what I do – Visual Basic and Access program development, it’s just amazingly fast.

Now, what I need maybe is a faster hard drive for my new system. u