First Looks At PCI-X, BTX, New Chipsets, And More

rsrsharma writes "AnandTech has some early bird Computex 2004 coverage up its sleeve. Included are the first pictures and partial specs of nVidia's NV45, the PCI-X (PCI-eXpress) successor to the 6800 Ultra, and ATI's PCI-X cards. Also shown are Intel's new 9xx line of chipsets and LGA-755 motherboards, BTX form factor (the successor to ATX) motherboards, and much more. I'm definitely looking forward to this stuff." Update: 06/01 01:08 GMT by T : Several readers have pointed out that PCI-X properly stands for "PCI Extended" rather than "PCI Express."

PCI-X != PCI express

[Blaskowicz]

As usual there's some confusion between PCI-X (64bits PCI up to 133mhz) and PCI express which is a serial bus. Please call that PCI-E or whatever!

Error in summary

[Anonymous Coward]

PCI-X and PCI-Express are NOT the same thing!

Easier Reading

[evilmuffins]

If you don't feel like clicking through a hundred pages, use the "print" link instead. [anandtech.com]

PCI-X /PCI Express

[Anonymous Coward]

IIRC, PCI-X is just an extension of the PCI standard up to 133MHz (true PCI-X) with some other protocol tricks. PCI Express is to be a serial standard capable of Gbps speeds (2.5Gbps per channel). PCI - eXpress - I dunno what this is...

PCI-X / PCI-Express

[OmniVector]

I'm quite certain PCI-X and PCI-Express are two totally different things. PCI-X is a 64bit PCI port, that is backwards compatible with PCI. PCI-Express is a whole new device connection port with the goal of replacing PCI, PCI-X, and AGP. Thus, you don't call PCI-Express PCI-X.

PCI-X != pci express

[cheese_wallet]

PCI-X and PCI Express are not the same protocol. PCI-X is still a 32/64 bit parallel bus that handles FIFOs a little differently than PCI (i.e. the master can transmit unless the target has enough fifo for a complete transaction). It also changes the timing of the bus to allow for speeds up to 133MHz.

PCI Express is a serial protocol.

Re:What's the deal with BTX?

[prisen]

AnandTech [anandtech.com] has a halfway decent article on the spec. Good summary of what it is and who it's aimed at. As I understand it will eventually be mainstream, where ATX will be phased out just like AT was.

Re:Nice...

[tokachu(k)]

I'm assuming you're talking about NICs (I for one need quite a few PCI slots myself for the thing). The newer tower computers (early 2005) will probably have lots of PCI slots, one AGP slot, and one PCI-X slot. Small-form-factor computers will have one of each.

It also kinda irks me when I see that PCI-X will not be in any way compatible with older PCI cards. They ought to change the name. This is a good technology, don't get me wrong; this speed is needed for both the newer video cards and gigabit and 10-gigabit network cards of the future, but when people try to stick in the old PCI cards that their cable/DSL provider gave them into those slots and find that they don't fit, they'll be making a call to the manufacturer wondering why a PCI card doesn't fit in a PCI-X slot.

A bureaucratic nightmare, indeed. Change the name, Mr. Industry, or you'll regret ever inventing tech support.

It should be noted that Mr. Anand mostly focuses on the gaming industry. I knew him back when he was in high school and he only looked at new technology if it would help him get his game on. So for mainstream society and the people who use game consoles instead of PCs, this isn't necessarily news.

Re:Nice...

[rsrsharma]

Eventually, PCI-X will be used for everything. Right now, however, the only cards that actually needs the extra bandwidth it provides are graphics cards, so they'll function like AGP.

PCI-X is not the same as PCI-Express

[Theovon]

PCI-X is a 133mhz bus which is backward compatible with PCI and PCI66.

PCI-Express is a system bus but is more of a networking protocol using high-speed differential signaling (like DVI and SATA) as the physical layer.

PCI-X and PCI-Express are similar only in name (and some similarities in how "config space" is handled). They are really two radically different things.

My Apologies...

[rsrsharma]

It looks like I got my terms mixed up. Sorry everyone! For those who are confused know, here's what I think the difference is:

• PCI-X: 64bits PCI up to 133mhz
• PCI Express: Serial bus, a replacement for AGP (mostly), and for graphics cards (at the moment). What I accidentally called PCI-X (PCI eXpress)in the article. From other articles I've read, it looks like it'll be used for all cards eventually. Although I still think this acronym makes more sense than PCI-E, I guess it'll confuse some people who have actually heard of PCI-X before. I have this wierd feeling that the industry is gonna call PCI Express PCI-X now (it sounds way cooler).

Some other info on PCI Express:

• There can be different sizes of slots. All the graphics cards use x16 size slots, while it looks like most other types of cards will use x1 size slots.
• It will eventually become ubiquitous like PCI
• More information in this article [anandtech.com].

I'm sure I got something wrong, feel free to correct me.

Re:BTX you say?

[RedWizzard]

Those two motherboards are both picoBTX boards, designed for small form factor systems. Not all BTX stuff will be that size just as not all ATX boards are microATX or FlexATX sized.

For more info on BTX have a look at this AnandTech article [anandtech.com], or check out FormFactors.org [formfactors.org] if you want to look at the actual specifications.

Re:Nice...

[pantherace]

Ummm, you are getting your standards confused. PCI-X is a fine name for what it is.

PCI Express is not compatible with standard PCI, however PCI-X is (just higher clockspeeds (up to 533) & a 64-bit interface)

Re:Someone explain please...

[afidel]

Yep, they are usually to make different traces either equidistant or to introduce necessary delays. Another reason to use non-straight paths is to avoid RF interference and induced current between PCB layers. Also hard bends in a trace can often lead to leakage and singaling problems so you might need two smooth curves to avoid a single hard corner.

Re:No for transitioners I guess.

[irokitt]

The slots are tiny because PCI-Express is a serial protocol, unlike PCI or ISA which are parallel. Only the graphic card slots need more data paths.

As for doubling PCI-Express cards next to normal PCI slots, most of the boards you see pictured do that. They seemed to average 2 PCI slots, 2 PCI-Express x1 slots, and a PCI-Express x16 slot for a graphics card. And many of the motherboards also supply an AGP slot for people who want to use one of the AGP-dependant cards that are out now.

For me, the most curious thing was seeing a motherboard with two different CPU sockets, but that isn't a dual-CPU capable board. Kinda creepy.

Re:BTX you say?

[Blackeagle_Falcon]

I believe the boards are all "pico"BTX meaning they're built for Small FormFactor (SFF) PC's. Such as the one's Shuttle Makes

These are picoBTX boards (one expansion slot each), but I don't think picoBTX is intended for SFF machines, according to an earlier Anandtech article [anandtech.com] picoBTX is still 8" x 10.5", awfully big for an SFF machine.

Shuttle will probably continue using their own custom motherboards for their designs.

Hence the lack of expansion slots.

The microBTX and BTX sizes will have more expansion slots (up to 4 and 7 slots respectively).

Re:Someone explain please...

[csirac]

I've never designed a high speed digital board before, but I guess it's to compensate for the transmission line effect.

Let's pick a number. Say 500MHz. Depending on dielectric constant of the PCB substrate, thickness, etc. a ball park figure for the speed of a signal propagating along one of those traces is around 70% the speed of light, so 2.1E+9 m/s. That makes the 500MHz signal have a wavelength of about 4.2m. Now, consider a 20cm trace. That shouldn't be unrealistic on a video card, if you actually followed one around on the PCB, it could be longer.

That trace has delayed the signal by 17 degrees, or 0.05 of a wavelength, which may or may not be significant. If we have the 64 data lines in a 64bit bus all different lenghts, you can see that different bits are going to "arrive" at different times.

Transmission line theory is a black voodoo art, where you can do all kinds of neat stuff like "create" reactive components and make matching transformers (impedance matches) or filters (different goal, same method) on your high frequency PCB just by making a carefully calculated sudden change in track width, plus the necessary "stubs"...

This all very over-simplified, but yeah, the squirly bits are to keep them all the same length (my guess). I'd be very worried if digital circuits needed impedance matching transformers made out of microstrips ;-)

Re:ummmm....

[Graff]

I'd like to keep using my PRINTER when I next upgrade my computer: heck, my old laserjet 4L is still alive and kicking after 10 years of valuable service.

Just get a Ethernet <-> parallel print server [netgear.com]. Then you can still use the printer with any computer that has Ethernet. Plus you can use it with any computer on your LAN without needed an active computer to share the printer

Re:Nice...

[hattig]

PCI Express IS NOT PCI-X.

This has been said 100 times on here at least in the past.

PCI-X is classic old PCI running very fast and 64-bits, etc. As used on server motherboards.

PCIe is the new specification with the tiny connectors for general I/O, and longer connectors for graphics.

There is no limitation on PCIe connectors unlike AGP, apart from the chipset. Each slot is point-to-point, so you need a controller for each one.

Here [theinquirer.net] is a motherboard with two PCIe slots (x4 and x16), a standard PCI slot, and 3 PCI-X slots.

Re:explain please

[hattig]

LGA-775 is getting a lot of flak because of reliability rumours. However it will be more suitable for higher clocking processors from Intel and is needed.

PCIe 1x is 250MB/s in each direction. That's enough for a dual Gigabit ethernet card, and each slot gets dedicated bandwidth.
PCIe 4x is 1GB/s in each direction. Eight port GigE ethernet card anyone?
PCIe 16x is 4GB/s in each direction.

(those will be new adjusted megabytes of 10^6 bytes, not 2^20)

Look at the extra space on the motherboard when the 1x slots are used as well - should allow more more on-board goodies or smaller boards.

BTX is Intel's idea. Because of their stupidly hot processors. Looks like it will flop badly.

Dunno what the brown slots are. Thought they might be AMR or CNR or something. They are only test boards though - see the edge connector?

PCI Express is backwards compatible with PCI &

[olePigeon (Wik)]

PCI Express is software compatible with PCI and PCI-X, but the physical connection is different. There are already specifications [pcisig.com] available for PCI Express-to-PCI/X bridge, so you need'nt worry about your "legacy" PCI devices becoming useless after PCI Express' adoption.

A source of confusion...

[anethema]

While PCI-X stands for PCI-eXtended, which is just 64 bit (and 133mhz?) pci, this is NOT the technology they are talking about in the article. PCI-X is a very expensive implementation as it requires one controller chip per slot, so you will probably never see this in the desktop market.

They ARE talking about PCI-Express (formerly 3GIO or 3rd Generation I/O), which is a whole new standard, but will remain backwards compatible with any newer PCI (2.2) card. PCI-Express is a serial, point-to-point bus, needing only 4 traces per connection, instead of PCI's 32. It has a theoretical transfer rate of 2.5Gb/s in each direction, tho who knows about real transfer rates. Also, you can stack 'lanes', for slots that need more bandwidth(like the video card slot, which uses 16 lanes afaik), giving you your full-duplex 2.5Gb/s per lane.

It is a packet-based protocol like AMD's hypertransport,and ethernet, and the controller will have a type of 'switch' similar to an ethernet switch for interfacing with all your devices. The advantage of this is your peripherals will, if designed to do so, be able to communicate to eachother directly, wihtout burdening the cpu or memory bus.

Also, PCI-Express is -supposed- to be hot-pluggable or designed with hot-pluggability in mind, but we'll see how well that works in practice...didn't seem to be too hot with serial-ata hard drives.

Hope that helps..

Re:ummmm....

[hahn]

...or if you've gone wireless get a wireless print server [d-link.com].

Re:Mac's already use PCI-Express

[iocon]

I'll go on and say this then... Macs (new ones) have PCI-X (which as everyone has stated is not PCI express). I saw PCI-X on Xeon boards well before Apple shipped a box w/it.