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PCI Express - Coming Soon to a PC Near You
Max Romantschuk writes "I've been following the emerging of PCI Express for some time now. PCI Express, previously known as "Third Generation I/O" or "3GIO", is the technology set to replace PCI. PCI has been with us for around ten years now, and is rapidly running out of bandwidth. Last week Anandtech ran an interresting story on PCI Express. The techology has previously been covered by Hexus and ExtremeTech aswell. I feel this technology looks all set to replace PCI, and we really do need some new bus technology to keep up with the bandwidth demands of today's applications. Or is this just yet another way to force us into a new upgrade cycle?"
Excuse me for being dumb, buy why is everything going serial over parallel? I.E. Why is serial transfer faster than parallel transfer?
Or is this just yet another way to force us into a new upgrade cycle?
:)
Or maybe current PCI devices don't support DRM out of the box ? Please upgrade your bus techno, so we can use all this extra bandwidth to transfer huge crypto keys to/from your hardware, just in case you want to play a copyrighted sample on your soundcard
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I'd say a new standard every 10 years is a pretty reasonably upgrade cycle compared to most other PC technologies...
OK, so yes we can probably live with PCI for longer (possibly much longer), but why not introduce a new standard with better potential? It maintains complete backwards compatability with regular PCI components, so manufacturers of harware don't even have to change anything. Of course another issue is motherboard cost, but there will always be new features put into successive motherboard generations that aren't in widespread use yet... like serial ATA, gigabit ethernet, etc. And there will probably be motherboards available for a lower cost without those features as well.
It looks like Linux developers are already working on support. Also, the Inquirer reports that PCI may kill AGP?
Exactly, check out the i875 chipset design on the 3rd page of the anadtech article and everything there without using pci, with a springdale/canterwood/nforce2 even, motherboard everything but the kitchin scsi is built in, expansion cards are becoming useless on average machines as proved by the huge growth of laptops and small form factor computers. As long as the agp slot keeps up with the pace then graphics cards will be happy and pci/pci-express cards will only be useful for workstation/server machines. Can anyone actually think of a useful expansion card that wouldn't duplicate something on a new motherboard (occasional firewire ommisions and scsi excluded)?
I think the point is to start off a discussion, since the discussions are often more interesting than the news item in the first place.
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Based on the direction in which mass-market computers are moving, the bus that gets exposed to the user is getting somewhat less important. Aside from gamers and tinkerers, and people who manage big servers, how many computer users ever have a need to open up the case?
Ten years ago it was almost a given that at some point, you (or your Computer Guy) had to add or replace one of the cards -- add Ethernet, upgrade the video, whatever. Nowadays, the hardware on-board is more than sufficient, and any of those "special" accessories you get, such as storage drives for your digital camera, or a scanner, or whatever, are more likely than not going to be USB or FireWire.
It's very likely that the mainstream desktop computer is going to move to a slotless "brick" form factor. This would have the side benefit of making it much cheaper. This form factor is available already, but it's not yet cheap because it's still considered a "specialty" unit.
I'd also be happy to see the return of the Commodore 64 form factor -- just shove everything into the keyboard. Plug in your mouse and monitor and Ethernet, and go.
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But I like to upgrade!
I usually build two computers a year. If I sell my computer every six months at 75% (which is about the going price) of its original price, I can keep up experimenting with sweet new hardware.
As an added bonus, I've built an expanding network of friends, friends' friends and practically unknown people who have been referred to me by the others. They buy my second hand computers, consult me whenever they want to buy a computer and have me build computers for them. I do it free, although sometimes I ask a steady "customer" to buy me some interesting item as a nominal fee for my services.
It's great fun! Yes, I tend to lose some money but most hobbies will cost you something.
BOO! TERRO
Hmm, let's see, on a desktop PC, you have:
some IDE controllers, each of which can push maybe 50MB/sec to the media (RAID-0) tops.
audio, keyboard, some other I/O, maybe 1 MB/sec
NIC, 10MB/sec tops
Ok, so I do the math and get 61MB/sec, or just under 1/2 the bandwidth of PCI. For 90% of the PCs out there, this is sufficient. For high end boxes, you can use 64bit or 66MHz PCI, or PCI bridges.
Tell me again why this technology is necessary?
I want to delete my account but Slashdot doesn't allow it.
"Or is this just yet another way to force us into a new upgrade cycle?" Yesssss, and that is ALL it is. Nothing will be gained, compatibility will be lost. May as well wait until the 256 bit processors come out.
About the only stuff that has made it into the chipset are cheap soundcards (yes creative is cheap to) and some extremely cheap raid solutions. A lot of other stuff is still in one form or another on the PCI bus. Even if it is not included on a plugin board.
So yes there is a real need for it. Simple example? Raid disks. With striping (multiple disks working together) it is now very easy to saturate the PCI Bus with the cheapest disks.
Same with gigabyte ethernet.
Of course it will be a long time before any real replacement will happen if ever. If I look at some of my old boards on top of the bookclosset I can see it took a long time before ISA was off, and I also see some odd really short slots I never used or seen cards for.
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One high end hard disc delivers 50MB+/s.
One gigabit Ethernet card can do >80MB/s
Together they are limited by PCI.
Now try Raid, TV-Card with PCI-OVerlay, GFX-Cards (Yes, they need a few 100MB/s)...
Plus remember that you NEVER EVER reach 133 MB/S with PCI. Even a single device can be happy to get 110MB with long bursts, and if you have many devices, effective total bandwith is more like 66 than 133 MB/s.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Server hacks like the 66-MHz PCI bus speed and 64-bit-wide PCI are neither practical nor sustainable. That's why we need something different, something like PCI Express. It raises the I/O bar enough to give us another few years of unconstrained growth of the PC architecture.
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PCI Express is packet based which makes operation of memory mapped devices across it exceptionally inefficient, both in bandwith and latency. So I would be suprised if PCI Express replaces AGP, where the primary interface is a huge direct-mapped on-board memory that video drivers directly paint the desired picture via massive use of load and store instructions.
.. all naturals for packetized transmission.
Where PCI Express will really shine is in block transfer devices such as HD and CD-ROM and high volume streaming devices such as those producing video and audio streams
- IDE harddrives (up to ~60MB/s)
- AGP graphics card
- Fast ethernet LAN (10MB/s)
PCI does 133MB/s.IDE chips are onboard and don't need PCI slots.
Gigabit ethernet could be a use of buses faster than PCI but I've felt the trend is also to put them right on the mainboard. Besides, the switches are still prohibitively expensive.
AGP: We've seen that 8x AGP does not give a performance boost over 4x AGP.
I don't see a great need for PCI-X at the moment.
I scanned the articles checked for anything on this, but didn't find a suitable answer. Will "PCI Express" be like USB, wherein it will support the older gen hardware as well as the newer hardware - or it will only support "Express" PCI devices?
It would be very nice to maintain a PCI port that was capable of faster speeds but still able to run old devices (somewhat like AGP 2x/4x/8x or USB 1.0/1.1/2.0 ramping up, ignoring recent USB developments).
I still remember one of biggest pains in my backside was trying to run PC's that needed an old ISA device (Scanner interface, old ISA SCSI card, special controller card, whatever) which I have heard is a drag on the whole system. Nowadays, I've got only PCI and AGP, though my old but still very good ISA SCSI scanner is still plugged into my 1Ghz Duron (with a single ISA port).
Will we get the best of both worlds? If express supports normal PCI, we can replace the old stuff in a jiffy. Running mixed slots again might be a pain, though.
PCI has been with us for around ten years now, and is rapidly running out of bandwidth
Are you *sure* it's running out of bandwidth?
The old-time, 10-year old 33 MHz, 32-bit PCI bus is still handles 99% of all home users just fine. However, for the more bandwidth-hungry users, you can increase the width to 64 bits. Not enough? Double the frequency. Still not enough? PCI-X will run them at up to *133 MHz*.
Let's put some numbers to that. On a 32/33 bus, you're looking at a maximum real-world, sustained throughput of about 100 megabytes/second. Double the width, that's 200 megabytes/second. Double the frequency, that's 400 megabytes/second.
Alrighty, then. Nearly a half of a gigabyte per second. That's awfully tough to fill. That will handle two gigabit ethernet controllers running full-tilt, and still have enough bandwidth left over that you'd need at least an INCREDIBLY fast RAID array to fill it.
But, just for fun, let's say it's still not enough. PCI-x, at 133 MHz, will double that *again*, to a full gigabyte per second. On a single controller. You're going to have an *INCREDIBLY* tough time actually using that - you'd be very hard pressed to actually get that much to move over a network and/or disk.
Still, you need more? No sweat. Many boards offer more than one controller. With two PCI-x controllers, that's two gigabytes/second of bandwidth. Not two gigaBITS, but rather two gigaBYTES.
Tyan recently introduced a board that has four gigabit controllers, each on their own PCI-x controller, with an additional 64/133 controller, a 64/100 controller, and a 32/33 controller. Again, let's put some numbers to that:
At 100 MB/s for each of the gigE controllers, that's 400 MB/s right off the bat. Add in the 64/133 controller, that's about 1400 MB/sec. Add in the 64/100, you're looking at about 2200 megaBYTES per second.
Now, really... can *anyone* here raise their hand and say that they could actually *utilize* 2200 megabytes/second of bandwidth to the outside world, either via network or disk?
Despite all of the ideas of the sky falling, PCI has done a very good job for the last decade, and amazingly enough, is still going strong. Strong enough that it will be quite a while before it truly NEEDS to be replaced.
Now, when it *IS* replaced, I'd much rather see the interconnects being optical, not electrical. Instead of cracking open the case, shutting off the power, and trying to wedge yet another card inside (especially in low-height rackmounts), I'd much rather set the device on a shelf, and run a fiber patch cable over to the computer. No shutting down, and a whole lot more simple.
steve
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