AMD Going Dual-Core In 2005

gr8_phk writes "We recently learned of Intel's plans to go dual-core in late 2005. Well it seems AMD has decided to follow suit. It should be noted that the K8 architecture has had this designed in from the start. Will this be socket 939 or should I try to hold out another year to buy?"

Comments

Re:Why not quad core?

[AuMatar]

You mean 8. This is a computer, you're legally bound to use a power of 2.

Re:You'll need a new motherboard.

[MBCook]

Nope. Sorry.

I understand your reasoning, but according to this article (I found the link on Ace's Hardware) the dual core chips will be compatible with current motherboards and sockets with as little as a BIOS flash (to recognise the new CPUID I assume). The downside of this is that the two cores will SHARE the dual channel memory bus. But because the bus is so effiencent, each core will probably STILL get more bandwidth than most P4s. At worst it shouldn't be much worse than having two single channel Athlon64s (which also are often faster than the P4). I think this is FANTASTIC news. For one thing, this means you could put FOUR CORES in that dual opteron SFF PC that was revealed a short while ago.

Really, it only makes sense. A dual channel processor has 939 pins, a single channel has 754 pins. So while some are power, you're looking at about 190 pins for the second memory channel. So that would mean that to have two cores on one die with their own memory channels, you'd need 1120 pins or so. That's a LOT of pins.

Instead of that enginering nightmare (you'd probably need 7 layer mobos to support that), we get drop in replacements that meet the same thermal requirements. Just think. You're dual operton not cutting the mustard any more? Buy two processors, drop 'em in, flash the BIOS, and now you've got FOUR processors without a new mobo or anything. All you'd have to worry about then is software licenses (unless of course you don't use any software that requirs that, for example you're all open source).

So to answer the grandparent's question, I'd say buy now. That said, I'm not sure if socket 939 will get dual cores or if it's only for 940s. I assume 939 will get them too.

Speculation: I'd like to know if the dual channel memory controler is shared by the two cores (like some kind of cross-bar architecture thing like nVidia used to promote) or if each core got exclusive access to one of the two channels. My guess is the former.

More speculation: Will there be a socket 754 dual core? That'd be cool, and I don't think the performance would be too much of a problem memory wise, unless you were doing memory intensive tasks. For CPU bound tasks I think you'd be fine.

Re:Just get...

[JWSmythe]

I agree.

I got to drive one of the nice newer Mercedes coupes,with a big V8 in it. They were bragging up the horsepower, so I was wanted proof. "Let me drive." I ran it hard. The owner, in the passenger seat, was impressed with the power I was pulling from it. Then asked the owner how much the car cost. Something around $100k. I handed him the keys to my car (2000 TransAm WS/6) and said "now drive this."

I paid about $25k for my car. New it was something like $30k. My car has better handling, better acceleration, better braking, and is faster. This was before I did any mods to it. The interior trim may not be as nice, but my car does have all the options including leather seats, and it turns more heads when I drive past, than a Mercedes does. It's comfortable enough for two people to ride in it all day (done that many times), and the back seats are just about as big.

Apple's are very pretty. I've used a few. I was happy that my girlfriend was on one using OS/X, but when that machine started acting flaky, we didn't buy a new Apple, we spent $1500 on really good parts. AMD 2800+, 1Gb RAM, 200Gb hdd, DVD reader, DVD writer, asus motherboard, high end video card, etc, etc.. What Apple does $1500 buy you? When we want faster, all we have to do is buy some faster components. When the G6, G7, or whatever comes out, well, you're buying a new Apple.

You can buy a new Mercedes at the really fancy store, or you can (could) buy a TransAm at any dealership. If I want more power, I grab Jegs or Summit, and start shopping.

You can buy an Apple at the fancy Apple store, or buy parts from a wholesaler whos "Will Call" area is the back door of the warehouse.

I still say "Pretty" every time I look at a Apple. I give them that. Then I hop back on my x86 based Linux machine and drive faster. :)

Exactly my first reaction!

[PaulBu]

But then, the trick is that he did not mention memory latency, only bandwidth! Getting the latter is relatively easy -- just make memory bus wider (as given bus speed), trying to decrease latency will pretty soon make you run into speed-of-light limitation.

Maybe those processors do have enough memory bandwidth to load two of them completely doing SAXPY? Assuming 12 GFLOPS sustained (3 GHz, 2 cores, separate ADD and MUL on each) you need to feed input vectors at 12*8 bytes/double = 96 GB/sec, for, say 1 GHz memory bus it is translated into 96*8=768 memory pins only for input -- well, wider than I've seen on desktop PCs... ;-)

When you start doing anything else , the roundtrip time between processors and memory (latency) becomes more important than raw bandwidth.

Paul B.

Re:Really nice alternative to dual processor syste

[NerveGas]

Multithreaded and multi-process.

If Firefox is rendering a page, you've got Firefox doing the rendering, the GUI working with video drivers, disk drivers looking at/updating your browser's cache, kernel code managing disk cache, kernel code managing network activity, and perhaps even firewall code running.

Whether you use Linux or Windows, there are a LOT of things running that you don't see in normal process list.

Now, will dual CPU's speed up that render time in Firefox? Not to any significant amount. But having used a LOT of dual-CPU systems, I can say that under heavy load, the machine will be much more responsive. If that helps your workload, it might be worth it. If it doesn't, it's not worth it.

As an example, at work I have a dual AthlonMP 1800+. At home, I have a single AthlonXP 3200+. For what I do at work, the single-proc chip would suck rocks. For what I do at home, the 1800+ would not compare to the 3200+. It's all about your usage.

steve

Re:Does dual core mean dual licensing costs?

[NerveGas]

Forget dual cores. What about Xeons, with Hyperthreading - where the system "sees" two chips? Nothing like paying a dual-processer license so that you can use a single chip.

steve

Integrated memory controller

[charnov]

Because the K8 has the memory controller on die, as you add processors, you actually add memory bandwidth. It kinda stands the old logic on its head. Really the only thing that can be an issue on this core is latency can make a difference at 16 CPUs or more ;-)