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Thoughts on PCI Express


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Thoughts on PCI Express
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Snoopy
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Join Date: Jul 2004
Location: Portland, OR
 
2004-07-18, 19:25

I've been reading a little about PCI Express and there seem to be some interesting possibilities for it in the Mac. Since I don't have enough technical knowledge to really evaluate these ideas, I thought I'd post them and see whether they can be shot down as unworkable or impractical.

Free (almost) Expansion Slots

Apple has not been eager to put expansion slots in consumer desktop Macs. Yet with Express, they may be almost free and Apple might reconsider. It appears that X16 PCI Express slots will be the future for Graphics cards. AGP is on the way out, but will linger for a while. It seems that Apple may use X16 PCI Express before long for all its Graphics cards. So here is the idea.

Once PCI Express is on board, it has a lot more channels than the 16 for graphics. Apple could add expansion slots for just the cost of a tiny X1 connector and cover plate for each slot. The cost should be insignificant. Since Apple has no recent history of offering expansion slots in this market, there is no need to have anything but PCI Express. The X86 PCs will be burdened with bridge circuitry, going from PCI Express to standard PCI, and additional standard connectors. In this way, the Mac could have a real manufacturing cost advantage.

Expansion Slots in a Very Low End Mac

PCI Express might be applicable in a very low cost Mac too, if Apple ever decides to makes such a product. At the very low end, the graphics performance can often be sacrificed for many uses. There are many undemanding applications that don't need much from the graphics chip. Yet, if a low cost Mac like this had an X16 PCI slot for graphics, there may not be a cheap enough card for this market. Most cheap PCs on the X86 side have on-board graphics chips from what I hear. So here is the question.

Is there anything inherent in an X16 PCI Express slot that would prevent it from interfacing with a very low cost and low performance graphics chip? If not, Apple could contract out for someone to build them a really cheap X16 PCI Express graphics card, to go into the lowest performance and cost option. Of course Apple can offer better graphics cards for this model Mac too, at a higher price.

Thanks in advance for all criticisms.

Jerry
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nowayout11
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2004-07-19, 04:23

I'd love an expandable consumer Mac.

I think if there's one hurdle, it would be the cost in establishing a market for "aftermarket" products, since there currently isn't much of one.

For example, the major graphic card developers only make Mac-compatible hardware on Apple's request because aftermarket sales are too small to bother getting into. And this issue may be unavoidable unless and until Apple pulls out of their 5%... or at least until they become a viable gaming platform in the eyes of hardcore gamers.

It works in PC land since PC users are used to choices. Apple holds a pretty tight grip on their platform. They'd have to loosen up the reigns as well.
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hmurchison
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2004-07-19, 04:48

I don't think Apple will have any inheren advantages over PCs in PCI Express. Since there are so many motherboards in X86 land and chipset integration is so dense I doubt we see many PCI/PCIE mobos.

PCI express does seem to be having a nice effect on notebook GPU. Nvidia's MXM slot and ATI's Axiom seek to leverage PCIe for upgradable notebook GPU. I'm sure the serial nature of PCIe makes this more feasible than parallel PCI/AGP.

It seems that PCI Express motherboards will come with a maximum bandwidth and manufacturers will carve that bandwidth up as they see fit. For instance the nForce 4 chipset is supposed to support 32 PCI express channels in a 16x,8x, 4x,4x config. Maybe highend configs will have two PCIe busses for 64x total channels.

omgwtfbbq
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dfiler
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2004-07-19, 10:42

I think the significance of this technology rests primarily on the bandwidth for data returning from the GPU. All of a sudden the hardware relient nature of quartz extreme makes sense...
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Snoopy
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2004-07-19, 17:51

Quote:
Originally Posted by dfiler
I think the significance of this technology rests primarily on the bandwidth for data returning from the GPU. All of a sudden the hardware relient nature of quartz extreme makes sense...

Your comment is encouraging. I figured Apple would have X16 PCI Express graphics cards at some point, but if Express is a big advantage to Quartz Extreme these cards may come sooner, rather than later.

Now if Apple would just figure out that adding expansion cards is almost free, we might see slots in lower cost desktops. So far, nobody shot down this cost issue. When PCI Express is on-board for graphics, there are many more channels available. Each slot is just the cost of a small connector and piece of tin to cover the opening.

If most X86 PCs are also built without standard PCI, as hmurchison suggests, Wintel machines will share this same cost advantage. However, I'm not so sure. The information I read from Intel a few months ago seemed to suggest motherboards will have both Express and standard PCI. In that case, there is the added cost of bridge circuitry and more connectors during some transition period, which could last several years. The Power Mac no doubt will do something like this too.

With all the brains at Apple, surely someone can think of advantages to having expansion slots in lower cost desktop Macs. Even if the only advantage is an ability to market Macs as expandable, it's probably worth the near-zero cost.
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hmurchison
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2004-07-19, 17:57

I definitely agree Snoopy. Apple needs some expandibility in every model. While the basics of computing as of today (ethernet, wifi, USB/FW, Sound I/O) have been integrated into the system we're still seeing new uses for PCI crop up. My favorite are the new PCI HDTV tuners rthat are cropping up. PCI Express makes these type of cards much more feasible because of its upstream speed improvements.

omgwtfbbq
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Snoopy
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2004-07-25, 11:41

Many thanks to those responding to my thoughts on PCI Express. I'll push my luck and hope to get comments on a broader use of this new technology. The proposal is to have a new desktop models, whether Macs or PCs, that lets PCI Express provide all input and output. We can call it "total configuration" or TC for now, and it would give customers the ability to select only what they need, with no unused I/O. If needs change, it is easy to add or replace one or more cards. The TC approach is most practical in low and midrange markets, where it could cover a wider range of uses at lower cost than any other single computer model.

PCI Express appears to make TC easy and natural. Motherboards now connect I/O chips like USB and Ethernet directly to Express channels. So, whether such I/O is on the motherboard or on a PCI Express card, there is no difference in electronic components required to do the job. TC also gives flexibility to things as common as USB. A low cost office system might have a single card combining 10/100 Ethernet and USB. For a low end home system it might be a single card combining a modem and USB. For others, maybe a dedicated USB card with many connectors. The possibilities seem endless with all I/O on PCI Express cards.

A TC model would need other options too. There may need to be two of more choices of CPU to cover a range of performance and price sensitivity. Also, choices of optical and hard drives is needed. And least we forget, there must be a fairly broad range of graphics card performance. It's possible that the lowest cost and performance graphics is not available in an X16 Express card. In that case, a computer maker wishing to offer the TC approach may have to build their own low cost graphics on an X16 card.

Regarding cost, I'm guessing that manufacturing cost for each slot would be under three dollars US, just the cost of a connector and motherboard area. There is no added circuitry once a decision is made to have an X16 graphics card. Most slots could be X4 connectors if these serve X1 boards too. I think they do. A system with many slots would need some X1 connectors, since there are only 32 channels total. It would be hard to justify adding another 32 channels in this particular market.

IT folks may like the TC approach for yet another reason. No matter how robust the interface circuitry and connectors are today, they are not invincible. If USB other I/O is damaged on a motherboard, it may mean a new motherboard. With TC, it just means replacing a card.

A few ready made configurations for retail sales could be a smart move. A basic Mac home model, for example, might have one card with both USB and a modem. A digital home accessory box might containing one card with FireWire and Ethernet, plus iLife applications, which would not be bundled in the basic model. There could be one or two other ready made configurations for other markets.
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FFL
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2004-07-25, 12:09

I agree that it would be a great advantage in upgrading and especially in low-cost repairs, to put I/O ports on PCI Express cards.

However, there is no way Apple will release anything that doesn't have the standard ports of USB, FireWire, and Ethernet. The fact that all models in the line have those, is part of the whole Mac aura, and part of what makes compatibility with 3rd devices much more simple than on the Wintel platform.
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Snoopy
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2004-07-25, 14:40

Quote:
Originally Posted by FFL
I agree that it would be a great advantage in upgrading and especially in low-cost repairs, to put I/O ports on PCI Express cards.

However, there is no way Apple will release anything that doesn't have the standard ports of USB, FireWire, and Ethernet. The fact that all models in the line have those, is part of the whole Mac aura, and part of what makes compatibility with 3rd devices much more simple than on the Wintel platform.

Thanks for your comments. I am mainly interested in the "TC" concept here, whether it makes sense and is reasonable, so your remarks are encouraging. I suspect you are correct about Apple's I/O policy, but I can hope things change a little. Maybe Apple could have a ready made home configuration with the three I/O you mention and a graphics card with eMac performance. Apple might sell lower performance to enterprise and education on a built-to-order basis. That would be a good start at least.
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Gargoyle
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2004-07-25, 15:46

I have been looking around for a gfx card for my new PC games system. From the info on the nVidia site - I think is a safe bet that the 30" display will be driven by two cards both on x16 PCIe.

OK, I have given up keeping this sig up to date. Lets just say I'm the guy that installs every latest version as soon as its available!
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Snoopy
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2004-07-26, 12:31

Quote:
Originally Posted by Gargoyle
I have been looking around for a gfx card for my new PC games system. From the info on the nVidia site - I think is a safe bet that the 30" display will be driven by two cards both on x16 PCIe.

Would you please provide a link if there is useful information at that site. I would like to know how double video boards will be handled on PCI Express motherboards. Off hand it seems like a waste of channels to put both cards in their own X16 slot, which would use up all 32 channels. Yet that could be what is done if 32 channels is a great benefit. Anyone have information about such advanced graphics card applications? On the new Power Mac, one of the two cards for an Apple 30 inch display goes into a regular PCI slot I believe.
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Dave
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Join Date: May 2004
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2004-07-26, 13:02

Quote:
Originally Posted by Snoopy
On the new Power Mac, one of the two cards for an Apple 30 inch display goes into a regular PCI slot I believe.
There's only one card. Its cooling system is so big that it spills over into the space above the adjacent PCI slot.

Edit: Spelling/Grammar fix

Last edited by Dave : 2004-07-26 at 13:42.
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