A little follow-up: I just took a skim through the section of the Samtec catalog for high-speed board-to-board connectors. Just about everything in there has a 3 db corner at 9 GHz or higher, with pin counts up to 500. Some of them have internal ground planes and can pass single-ended high-speed signals from board to board while maintaining transmission line integrity.
With some more requirements, I could try to pick out some candidate part numbers and get pricing and more detailed technical information. With this sort of thing, it's essential to have good application notes so that the board layout doesn't cause discontinuities. Samtec's typical delivery time for samples is under a week. BTW, PCIe connectors are among their specialized product lines. I've never run into problems with Samtec obsoleting parts. Jack Carroll ----- Original Message ----- From: "Jack Carroll" <[email protected]> To: "Timothy Normand Miller" <[email protected]> Cc: "ogml" <[email protected]>, "Dieter BSD" <[email protected]> Sent: Monday, December 10, 2012 12:16:36 PM Subject: Re: [Open-graphics] Open Framebuffer board This is the central issue, I think. A piggyback board is the only way I can see a retrofittable plug-in GPU being practical. Why do you say signal integrity would be destroyed? There's been quite a lot of work on fine-pitch connectors that can pass differential transmission lines from board to board, and we're only dealing with digital signals, since the DACs and analog cable drivers would be either on the main board or in a remote adapter module located at the monitor connector. A piggyback connector could be standardized within OGP, and decouple the mechanical interface to the frame buffer board from the interface to the GPU IC packages. That would allow GPU designs to evolve over time, and plug into older main boards. I think the first question to ask is how many lines at what clock rate (or rise time) would be required to communicate with the GPU assembly. Can I assume LVDS signals? Finally, what do you see as the cost impact of dividing the product into two boards, besides the high-speed connector pair? I wouldn't expect a large increase in total board area, and area is the main cost measure in multi-layer boards. The price of the frame buffer board should come down, since it wouldn't need the area required for the GPU. Jack Carroll ----- Original Message ----- From: "Timothy Normand Miller" <[email protected]> To: "Dieter BSD" <[email protected]> Cc: "ogml" <[email protected]> Sent: Monday, December 10, 2012 9:09:41 AM Subject: Re: [Open-graphics] Open Framebuffer board "Just plug it in"? No. There's a slight chance that we might be able to fit a different FPGA to the same board, but there's no "just plugging in" with a ball grid array. We could make a daughter board, but the signal integrity would be destroyed, and it would bloat the expense considerably. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com) _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
