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Author Topic: SAM and other new hardware - missing modern graphics card slots?  (Read 6422 times)

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Offline billt

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The CPU chip used on SAM440 does not have PCIe built-in. Some other PowerPC chips do. If they use such a different chip on a future SAM design, then we're in luck. Otherwise they could use a bridge chip to get PCI to PCIe.

Now, the graphics cards are x16 slots, having 16 PCIe lanes. The biggest PCIe port on any SOC PowerPC CPU I know of is x8, such as Freescale's 8641d. AMCC may have one with x8, nto sure, I remember them having some x4s somewhere. Many are x4 or x1. You could still connect and use a graphics card to a smaller port, but you'd only have the performance of the x4 or x1 port it's connected to. I'm perfectly happy with that. I believe AMCC also has PCIe2 on one of their newest chips, which doubles the data rate on a single lane, so their x4 version 2 may be roughly equivalent to Freescales version 1 x8 port, but you need the graphics chip to support PCIeV2 top benefit from that, I think some do this now.

Now, the board vendor needs to decide if it's worth doing that. Do the customers that would keep them in business need or want PCIe? Or would the added cost make the board unattractive to them? The Amiga market today alone isn't going to keep them in business for very long... They may want to give us PCIe slots but cannot make a successful business of it. Or they may have something in design that we just haven't heard about yet.

You could use one of these in a PCI slot to have the equivalent of them putting it on the motherboard:
http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=5927#details
Bill T
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Offline billt

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Re: SAM and other new hardware - missing modern graphics card slots?
« Reply #1 on: November 13, 2008, 09:25:54 PM »
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coupled with an AMD SB750 southbridge


Is this possible? I know the Uli Electronics M1575 southbridge was intended to be used with AMD northbridge and was a standard PCI-Express endpoint, but Uli told me the M1573 was NOT a standard endpoint and thus could not be used with PCI-Express switches and things like that for an MPC8641 based design at the time. Does anyone know better than this? Wasn't clear if it could work connected directly to the CPU's PCI-Express port, it may have or may not have.

What is A-Link Express II? as seen in block diagram at:
http://www.tweaktown.com/news/9910/amd_790gx_chipset_with_sb750_arrives/index.html

Is the SB750 a standard PCI-Express endpoint device? If not, it may not be usable in your concept. I tried finding out this for the SB600 but never really did find an answer. Considering that M1573 was NOT, other A-Link devices also might not be. I was realy disappointed when Nvidia bought Uli. They became impossible to talk to at that point. :( Does anyone know if M1575 is still available/sold by Nvidia? They don't bother to answer my queries from an "embedded system platform designer".

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/46155_sb600_rrg_pub_3.03.pdf
kindof sounds like SB600 is not generic PCI-Express, sounds like it's specifically designed for AMD northbridge chipset.

http://en.wikipedia.org/wiki/Comparison_of_ATI_chipsets
says: "Note 1: A-Link Express and A-Link Express II is essentially PCI-Express x4 lanes, so that any PCI Express capable southbridge can be used (such as ULI M1573/M1575)." This may bea unidirectional situation, where PCI-Express standard devices work onteh Alink bus, but it's not clear that Alink devices work on standard PCI-Express bus. OK, "bus" is wrong word for PCI-Express, but I'm not going to go back and fix my mistake here. :p

http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_14603_14620%5E14623,00.html
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/42119_sb600_ds_3.05.pdf

If AMD's Alink southbridge chips can work as standard PCI-Express endpoint devices, compatible with a switch, I'd be very interested to know.
Bill T
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Offline billt

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Re: SAM and other new hardware - missing modern graphics card slots?
« Reply #2 on: November 13, 2008, 09:54:04 PM »
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I love that AmigaOS 4.1 has a home now but I'd hope that future boards would eliminate things like the FPGA and add PCIe slots instead.


problem is, many embedded industry customers like having FPGAs around. If that's who's paying the bills for this board development and keep Acube and friends in business, then that's how it's going to be.
Bill T
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Offline billt

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Re: SAM and other new hardware - missing modern graphics card slots?
« Reply #3 on: November 13, 2008, 10:24:19 PM »
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Regarding the ULI 1575, that one is being used in Freescale's "HPCN 8641/8640 Development board".


I'm curious how to get the chip or if they bought some some time ago and have them on a shelf somewhere. And US$5000!!! Yikes! Oh, another distributor only charges US$4000. Much better. :)
Bill T
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Offline billt

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Re: SAM and other new hardware - missing modern graphics card slots?
« Reply #4 on: November 14, 2008, 04:29:12 AM »
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So do people think that SAM will (eventually) go straight to PCI-Express and skip AGP?


Absolutely. You can get SOC (System On Chip) PowerPC processors with PCI-Express coming directly out of them. 8641, 8640, 8610, 440spe, and the 460gtx even has gen2 PCI-Express for double the bandwidth per lane. There's more than this small list too. Stick one of them ports to a x16 slot and plug in your graphics card. (These CPUs don' thave a full x16 PCI-Express port, graphics cards are generally x16 connections, but you can run just about any card from any port size, such as a x16 graphics card off a x1, or a x4, x8, etc. The x16 slot may not be fully connected, but electrically it's compatible and physically fits, so all is good, just does not give full bandwidth the graphics chip is capable of) And vice-versa, a x1 card will work in any larger PCI-Express slot, as will x4 and x8 work in slots larger than they are themselves. PCI-Express is popular because it's for more than just graphics cards.

To add an AGP slot, you either do the PCI bus in an AGP slot trick like Efika's adaptor (and I do not think that just any AGP card works properly due to voltage differences in newer AGP cards), or you make up some AGP/PCI bridge logic in an FPGA since that doesn't seem to be an off-the-shelf chip these days and run your AGP graphics card on a PCI bus anyway. From a motherboard perspective, if it's electrically PCI, might as well let the higher-volume customers put a standard PCI card in it... There's very little demand for AGP in the high-volume PowerPC market today, and nothing other than graphics used the AGP slot to broaden its appeal.

All works out that you're far far far more likely to see a PCI-Express graphics slot (even if not fully x16 bandwidth in the electronics) for future PowerPC motherboards than you are an AGP slot.

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Also, am I correct in thinking that you cannot plug an AGP card in a PCI slot?


Correct. They're physically different and run at different voltages and have some different pinouts. Like putting a square peg into a round hole. They made it different to help prevent less advanced users from putting it in the wrong slot and breaking something.
Bill T
All Glory to the Hypnotoad!