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At 12:48 AM 9/23/2003, Jeff Brower wrote: >Rick- > > > You need to read the C67 documentation. IIRC, it is not one pin that is > > off, it is the whole of the address bus that gets moved by one pin on the > > C67 between sizes... > >Ok. > > > I think you will need a different footprint for each size. I also think > > the C6711 will not handle sizes above some max, which may be 256K, but I'm > > not sure. > >We've tried 2, 4, and 8M x 32, and those are Ok in the same >footprint. Note that >difference between 4 and 8 is an extra column address line, so no extra >EMIF lines >need to be run from the C6xxx. Are you saying that you have used all of these in the same socket and they work? Maybe *I* need to reread the C67 docs! > > The bottom line is pick your vendors and see how they do it. I seem to > > recall Toshiba as being a potential second source for Micron. You may find > > more than one "standard", but I doubt that each vendor will be > > unique. They know that many companies require a second source. > >Thanks, I will recheck Toshiba. > > > You might also look at the newer tiny sTSSOP parts (Samsung among > > others). They were new about a year or more ago and should be in > > production by now. I think they are targeted to the laptop memory module > > market and are about half the size of a standard 56 pin TSSOP. Since they > > are for commodity memory, they should not be overly expensive. If you find > > anything out about these, let me know. If they are commonly available, I > > would like to take a second look at them. I believe there are also BGA > > parts (Micron, et al). > >Samsung seems to not have any x32 organization. > >Yes the BGAs are an option, and Micron has those. But they are definitely >expensive >and have a long lead-time. We are using BGA versions for some high >channel density >VoIP PTMC boards where their extra margin gets buried in the higher cost >of those >boards. > >-Jeff My point about Samsung is that you can get a pair of the sTSSOP packages (x16 organization) in the footprint of the x32 TSSOP package. This will give you more bits as well, if that matters. I seriously considered the x32 parts a year or so ago and spoke with FAEs and sales reps. But the x32 parts will always be a generation or even two behind the x16 parts and only having a single chip also cuts the density by 2. So using a pair of x16 chips in the sTSSOP package allows for at least 2x the bits and possibly 4x or 8x in the same footprint. Rick Collins Arius - A Signal Processing Solutions Company Specializing in DSP and FPGA design http://www.arius.com 4 King Ave 301-682-7772 Voice Frederick, MD 21701-3110 301-682-7666 FAX |
SDRAM pin-compatibility question
Started by ●September 22, 2003
Reply by ●September 23, 20032003-09-23
Reply by ●September 24, 20032003-09-24
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Rick- > Are you saying that you have used all of these in the same socket and they > work? Maybe *I* need to reread the C67 docs! I THINK so, but please don't hold me to it. I know that 2M and 4M x 32 parts work, and I think that one of our engineers tried an 8M sample a few months ago and it worked, but we've not done formal and rigorous testing on the 8M x 32 yet, so I can't be sure. > My point about Samsung is that you can get a pair of the sTSSOP packages > (x16 organization) in the footprint of the x32 TSSOP package. This will > give you more bits as well, if that matters. Yes it seems like 2x Samsung K4S561632E devices could provide 16M x 32 in the same board space as one Micron 8M x 32. Is there a 2nd source for Samsung's sTSOP2 packages? > I seriously considered the x32 parts a year or so ago and spoke with FAEs > and sales reps. But the x32 parts will always be a generation or even two > behind the x16 parts and only having a single chip also cuts the density by > 2. So using a pair of x16 chips in the sTSSOP package allows for at least > 2x the bits and possibly 4x or 8x in the same footprint. Yes I think you're right. My concern would not having used the Samsung devices before or having seen them on the DSK boards before, and what to do if we run into problems. -Jeff |
