PCI Slot Confusion

[JeffLancaster]

OK, what I need is someone to explain in detail the differences in these slot types and what's compatible with which. What I understand so far is that there are two new types of slots on motherboards which are rendering traditional PCI slots obsolete (PCI-X and PCI express). I understand that PCI-X is in some way backwards compatible with conventional PCI cards, but PCI express is not. However, looking at the specs and pictures of some of the newer motherboards, the slots certainly don't look the same. So I have a number of questions - hopefully someone can help me out here.

To use as an example, an Asus A8N-SLI motherboard has 2 "PCI X 16" slots, "2 PCI X 1" slots, and 3 "PCI" slots. I assume the 3 "PCI" slots are the conventional types, but what are the others, PCI-X or PCI express? Which type would a graphics card go into? The "PCI X 1" slots appear to be very short, but the "PCI X 16" slots are longer. So are these the PCI-X slots I hear about which are backwards compatible?

My main concern is understanding how future upgrades will be compatible with my current and future add-on cards. For example, my current motherboard is easy to figure out - I have 5 PCI slots and an AGP slot. The graphics card is in the AGP slot, and I have a firewire card and 2 audio interface cards residing in PCI slots with 2 more PCI slots available for expansion. For the near future I'm thinking of replacing one of my audio interface cards with either a Lynx Two or L22 card for very high quality ADA conversion. I'm also look at adding a UAD-1 card for high quality plug-ins and processing power. With my current motherboard, that would mean having four of my slots used, with the fifth one reserved to possibly add a second UAD-1 card at some point. However, if I then was to upgrade my motherboard to one such as I described above, it looks like I only get three conventional PCI slots (unless those PCI X 16 slots are somehow backwards compatible). That means either my firewire card or my auxilary audio card would have to go, and there would be no possibility of ever adding the additional UAD-1 card

Finally, while it seems that I end up upgrading my motherboard/processor every 2 or 3 years, I'm concerned that there may be a trend for conventional PCI slots to completely go away over time, which could leave me with some very expensive, but unfortunately useless, audio interface cards and UAD-1 stuff. Any comments on this?

 

[bennychico11]

well, before we dive into all that, look at the specs of the ASUS board again. They aren't PCI-X (PCI Extended) slots....they are PCIe (PCI Express). This is why you are seeing the difference in sizes. The sizes of the PCIe come in x1, x4, x8, x16 and vary in sizes are well. They make cards that fit the different lengths but you can also use the smaller cards in the bigger slots. The numbers next to the PCIe slots' name has to do with the "lanes" it transfers data on. The PCIe x1 slots contains a single lane which is composed of 4 data wires (one pair of transmit and one pair of receive).

And you're correct, the PCIe bus will not support the common PCI card that we are used to now.

 

[JeffLancaster]

Thanks Benny. Of course, I've seen video cards that use PCI express slots, and it seems that one of the PCI X 16 slots would be used for this. However, I have no idea what a second X16 slot would be used for, nor what the x1 slots would be used for. And I'm very concerned about the diminishing number of "regular" PCI slots on motherboards. I did read something about "PCI-X" slots having backwards compatibility with old PCI, and that was encouraging, however perhaps those aren't being installed on any new motherboards? Any more thoughts?

 

[bennychico11]

it's all up to the manufacturer of the video cards. They can make PCI, PCI-x or PCIe cards that will work for any motherboard, you just have to buy accordingly. Yes, I think we'll start to see PCI being phased out over time, but I wouldn't say it's necessairly a bad thing. PCI-x isn't really that new and I expect that will be phased out after PCI to make room for PCIe. In fact, the new G5s are using ALL PCIe. These are going to be well suited for any graphics card since it will carry faster throughput and be more reliable.
Just be careful when you buy your motherboard and make sure it doesn't have something you don't want. If you're not ready to upgrade to PCIe, don't do it yet....just beware that soon regular PCI motherboards will be few and far between.

 

[JeffLancaster]

Thanks again. So I guess my biggest concern is ending up with high quality, expensive cards from Lynx and UAD that won't be supported on future motherboards. I suppose those manufacturers may come out with PCI express versions of those cards, but I haven't seen any indication of this yet. I've resigned myself to the need to gut the PC and upgrade every 2 or 3 years (something I've done many times over now), but having expensive audio hardware like that become obsolete so quickly is much harder to swallow. Still wondering what to think about that? Do you think it will be possible to find a motherboard in 5 or 10 years that will support the CPUs and operating systems we will have then, and still be able to use my expensive audio hardware? Maybe I shouldn't even worry about it and just be saving enough money to upgrade everything every few years - I don't know. Any other thoughts?

 

[Creamyapples1]

I would say they will phase out PCI about like they did with ISA slots. Even today, on some boards you will still find the odd ball ISA slot still in the design but they are few and far between. I'd say in the future, PCI will suffer the same fate, at the same time manufacturers will transition to PCI Express and so on, but by the time this transition has reached its pinnacle, you'll want new soundcards anyway. I don't think this is something that is going to happen overnight, or even in the next 5-10 years. Right now, PCI Express is being utilized as the new alternative for video cards, while popular amongst the aftermarket crowd (not even close to a quoteworthy percentile of the PC using population), noone else is really biting. Having done little else research on the other facets of PCI Express, noone else is tooting their horn about PCI Express add-ons (soundcards, NICs, etc) so I'd venture to say the day that PCI is no more, is further down the road than you should probably be thinking about in regards to upgrading what you have now. Even when PCI-E does take over completely, You will have (or should, given the nature of the business and its history) ample time to ease into it.

Just my .02

 

[bennychico11]

so I'd venture to say the day that PCI is no more, is further down the road than you should probably be thinking about in regards to upgrading what you have now.

I do agree that I wouldn't throw in the PCI towel just get, but eventually there will be a time when people look at you strangely when you mention your old PCI or AGP graphics cards. In the audio interface world this may be even more of a reason to stay away from professional PCI sound cards and go with something like firewire, at least until the manufacturer comes out with the express cards. As far as the UAD-1....I think if you wait long enough they'll come out with a PCIe card because there will be a demand for it.
However, since Apple has put PCIe on their new G5s, and since Mac has become a sort of standard in the audio/visual world....more manufacturer's will start to offer it. Digidesign has already started offering the TDM cards in PCIe format.
It's not really a matter of IF it's going to happen....just when it's going to happen and will we have time to adapt. Like Creamyapples said, it's happened before and we adjusted just fine.

 

[dgatwood]

Thanks Benny. Of course, I've seen video cards that use PCI express slots, and it seems that one of the PCI X 16 slots would be used for this. However, I have no idea what a second X16 slot would be used for, nor what the x1 slots would be used for.

Second x16 slot: A second graphics card, possibly connected to the first with a special cable to link them together for better performance.

x1 slots: Pretty much anything other than video (though you could presumably use it for video, too, albeit more slowly).

BTW, It's PCI Express x16, or for short, PCIe x16. Please don't write it as PCI X16 (with a capital x), as that looks too much like PCI-X, which is unrelated.

And I'm very concerned about the diminishing number of "regular" PCI slots on motherboards. I did read something about "PCI-X" slots having backwards compatibility with old PCI, and that was encouraging, however perhaps those aren't being installed on any new motherboards? Any more thoughts?

Outside of the server space, I think Apple is the only company that ever built any computers with PCI-X slots. I don't know of any cards that took advantage of PCI-X, either, with the exception of a handful of a few RAID cards and weird server ethernet cards with 8 gigabit NICs on a single card....

 

[dgatwood]

Thanks again. So I guess my biggest concern is ending up with high quality, expensive cards from Lynx and UAD that won't be supported on future motherboards. I suppose those manufacturers may come out with PCI express versions of those cards, but I haven't seen any indication of this yet. I've resigned myself to the need to gut the PC and upgrade every 2 or 3 years (something I've done many times over now), but having expensive audio hardware like that become obsolete so quickly is much harder to swallow.

That's why I've been jumping up and down for about the last year encouraging people to buy FireWire or USB interfaces if they plan to spend over about $100 or so.

Still wondering what to think about that? Do you think it will be possible to find a motherboard in 5 or 10 years that will support the CPUs and operating systems we will have then, and still be able to use my expensive audio hardware?

Will you be able to get PCI motherboards in 5 years? Probably, though they'll probably cost a fair bit more. In 10 years? Maybe, but I wouldn't count on it.

Maybe I shouldn't even worry about it and just be saving enough money to upgrade everything every few years - I don't know. Any other thoughts?

Well, if you have a multi-thousand-dollar investment, you could buy a PCIe to PCI expansion chassis. Performance won't be quite as good as it would be internally, and it'll cost you about $1500 last I checked, but if you're talking about $20,000 worth of Digi hardware, I suppose it might be worth it....

Otherwise, your best bet is to avoid internal devices that cost over a couple hundred dollars (except video cards, which you'll presumably sell with the machine).

You can safely buy FireWire/USB devices, as you can safely assume that any external expansion will be supported for decades. I can still hook up an ADB or PS/2 keyboard/mouse to my Mac. I can still hook up a SCSI hard drive. I can't hook up a NuBus card (practically).

Not only can I get FireWire (for example) cards for PCIe, I can get them for ExpressCard (PCIe's replacement for CardBus). In fact, I think there is already FireWire bridge silicon to bridge to HyperTransport, which means that when we see the new external HyperTransport variant, we might very well see external boxes to adapt it to FireWire at blazing speeds. That should be good for a fair number of years.

The bottom line is that it is relatively easy to bridge an external bus to a more modern bus architecture, while it is relatively hard to bridge a card slot bus architecture to another card slot bus architecture. External devices, thus, will always be a safer investment than cards.

Oh, yeah, and that external HyperTransport stuff will probably eat PCIe for breakfast. That's where things are headed, I suspect. Thus, while PCIe is fine and all, I wouldn't spend money on an audio interface based on that standard, personally.

 

[JeffLancaster]

BTW, It's PCI Express x16, or for short, PCIe x16. Please don't write it as PCI X16 (with a capital x), as that looks too much like PCI-X, which is unrelated.

I agree, that's confusing. That's how it was written in the information I was looking at, which is one reason I was having a tough time sorting it out.

That's why I've been jumping up and down for about the last year encouraging people to buy FireWire or USB interfaces if they plan to spend over about $100 or so.

Sounds like a good idea, but unfortunately the UAD plugs need the PCI card to run - it doesn't come in any other formats at this time. And as far as a firewire audio interface, the best one I'm aware of as far as converter quality is the RME Fireface. It's a nice unit, but the Lynx converters are supposed to be better quality, and I really don't want to pay more money just to get extra preamps I don't need, and converters that aren't as good. Of course the next step up would be some Lavry or Apogee converters in a standalone box, but those are very expensive and would still require an AES/EBU card, which again, is PCI See why it's a dilemna? Of course, if you know of any other options I'm not considering, I'd sure love to hear about them.

Thanks to all of you for the input.

 

[Robert D]

I don't think PCI is going away any time soon. The ISA slot migration comparison is good to an extent, but PCI should have an even longer shelf life since it is software compatible with PCI Express, can share the same slot (slot, not connector), and is not as bandwidth challenged. Besides, by the time it goes away entirely, it's gonna be on some smokin fast MBs as the legacy slot, in systems that vastly exceed the requirements of any digital audio application.

 

[Minion]

If your Mobo has 2 PCI-E 16x slots then the Motherboard is "SLI" compatible which means that you can connect 2 seperate Video Cards of the Same Type in the 2 Slots and get twice the Graphics Power......

Most SLI Motherboard will have a Nvidia Nforce Chipset as the SLI Technoligy was created by Nvidia and only Nvidia Cards will work in a SLI Configuration...

ATI has a Simular Graphics Setup called "Crossfire" were you can run 2 Video Cards at once and each Card Processes half of the Screens Graphics which essentially gives you twice the Graphics Power....

There is really no reason to use any of these 2 Card Graphics Configs unless you are a Heavy duty Gamer and even then One High end card is good enough....

Cheers

 

[dgatwood]

I don't think PCI is going away any time soon. The ISA slot migration comparison is good to an extent, but PCI should have an even longer shelf life since it is software compatible with PCI Express, can share the same slot (slot, not connector), and is not as bandwidth challenged. Besides, by the time it goes away entirely, it's gonna be on some smokin fast MBs as the legacy slot, in systems that vastly exceed the requirements of any digital audio application.

Can share the same slot? How's that again? Yes, I vaguely recall that you might be able to do an x1 PCIe slot with a basic 32-bit PCI slot behind it, but that would be physically incompatible with any PCIe cards except for x1 cards, as it would have to occupy the same space. It would also be incompatible with 64-bit PCI cards, since the extra byte lanes use the same space as the x1 connector, IIRC. Am I missing something? Seems like a motherboard manufacturer would have to be smoking something to do that.

As for software compatibility... that's well and good, but the reason PCI is almost universally hated among hardware engineers is that it is a royal b*&^# to run parallel signal lines like that. It really limits the possible board layouts when you support parallel PCI. I think the people who design boards would love to be able to say "no PCI starting tomorrow". Apple's engineers already did.

I expect PCI to go much more quickly than ISA did. The only reason ISA took so long to die is because of the popularity of ISA cards in the home and office computing market, where upgrading those cards was (proportionally) more of a financial burden than it is now. I'll explain.

When ISA was around, nearly every PC required a sound card, a network card, a video card, a parallel card, etc. The reliance on cards was very heavy, and PCI machines generally did not have any more integrated devices than their ISA counterparts, so most users ended up bringing along their cards or eventually replacing them with PCI equivalents. The upgrade cost for consumers made it worthwhile for manufacturers to carry ISA along for a significant period of time.

These days, nearly every computer has built-in audio, USB, and networking. Video is either on the motherboard or is in an AGP (not PCI) slot, so even that isn't an excuse. And most video cards are PCIe native already, with the AGP versions suffering a performance hit by really being a PCIe device sitting behind an AGP to PCIe bridge. AGP is fading fast from a motherboard POV, though the cards will probably still be around for several years to support users with older motherboards.

I think I saw a statistic that on average, modern computers have only one PCI card. This probably suggests that the bulk of computer users have zero. The odds are also still skewed by older machines, which generally came with less built-in hardware. I'd bet the average for machines bought in the last year is in the 0.2-0.5 cards per machine range, not counting servers. In fact, I'd go so far as to say that outside of the server market, I suspect that the vast majority of computer users don't have any PCI cards and never will. Look at the percentage of Mac users who buy iMacs to see what I mean.

And, of course, in the server space, performance is a big deal, so in that space, PCIe is likely to obliterate PCI pretty quickly. When you're spending that kind of money on a server, unless you absolutely have to do a like-for-like board swap for a government contract, odds are you'll spend the extra dough for that nice, new PCIe RAID card instead of a standard PCI card.

Thus, with PCI, you have a very different market than we had when ISA was being phased out, and the cost advantages of dropping PCI for PCIe (easier board layout) are sufficiently large that I would expect PCI to become a niche much more quickly than ISA did. Outside of very specialized uses (and basically outside the realm of pro audio/video), there really isn't a market for PCI anymore and (servers notwithstanding) hasn't been for some time.