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Almost free RAM

Discussion in 'Electronic Design' started by John - KD5YI, Oct 28, 2005.

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  1. John - KD5YI

    John - KD5YI Guest

    I have 16 each NEC D43256-85L integrated circuits. I believe them to be 256
    (bits/bytes?) SRAM devices. They are in the 28-pin wide-body DIP package.
    Obviously, they are old, probably 1993 (if I'm reading the date code properly).

    I have no need for them. I would like to find them a loving home where they
    will be most useful. I will ship them to whoever is willing to pay the DHL
    shipping costs (shipping method is convenient for me so it is
    non-negotiable). The first respondent with the most dire need (if there is
    such a person/need), will get them. My zip code is 75074.

    Unmunge my email address to reply privately. If I hear nothing, either
    publicly or privately by Monday afternoon, I will make the ICs a home in the
    trash.

    Cheers,
    John
     
  2. Kryten

    Kryten Guest

    32K x 8 bits = 256K bits SRAM

    http://www.xs4all.nl/~ganswijk/chipdir/pinusr/43256.txt

    I have a lot of 32Kx8 SRAM and 256Kx1 DRAM.

    Maybe someone can think of a good application for them.
     
  3. John - KD5YI

    John - KD5YI Guest

  4. Guest


    I'd love those chips. RAM chips are hard to buy individually. You'd
    have to get them in bulk. SRAM chips especially more so since these
    days caches are built in to the CPU. And most modern cache and buffer
    rams on motherboards are DRAM since these days they are fast enough (up
    to 500MHz).

    I design and build CPUs as a hobby and SRAM chips are so much simpler
    to use since I don't need to do refresh. I usually get them off very
    old motherboards (pre 1998).

    Unfortunately, living in Malaysia means that the shipping will be very
    expensive for me.
     
  5. Ralph Barone

    Ralph Barone Guest

    Anybody have a 628128 static RAM they would like to send to a good home?
    I would like to update my Tandy WP-2.
     
  6. Kryten

    Kryten Guest

    Yes, I noted the way things were going and made efforts to grab DIP RAM
    while it was discarded in old PCs. I've got enough for the dozens of
    projects I have not thought up and don't have time to do... :)
    The CPUs themselves or boards using microprocessor chips?
    Which ones do you use, and do you have web pages?
    Design a good project on the web and maybe interested readers will donate
    chips you request. But only after the design is up, no point people moving
    stuff from their parts box to yours if they are not going to get used.

    Don't write off DRAM chips. They are not that hard to use. They use half the
    address lines, so you could add 8 or 32 K storage to a small microcontroller
    project.
     
  7. Kryten

    Kryten Guest

    Have you checked the socket and the machine will accept this chip?

    http://www.larwe.com/museum/tandywp2.html
    has a full 13MBytes service manual with circuit diagram.

    I can't see a DIP socket for RAM on the board:
    http://www.larwe.com/museum/img/wp2-comp-l.jpg
    There is one DIP socket but it holds the ROM.

    Or does it sit in the IC card slot?
     
  8. Guest

    Yes. I have some Hitachi HM628128LFP-7 128K x 8 SRAMs in the so-32
    package (0.5" wide, 0.05" lead pitch), carefully removed from working
    boards by yours truly. If suitable, I'd be happy to send a couple to
    one of my lovely northern neighbors.

    James Arthur (e-mail address is good)
     
  9. Rich Grise

    Rich Grise Guest

  10. Guest

    Hey, nice site! It's always nice to see old computers well-loved
    & supported.

    It seems he needs a DIP package rather than the so-32 I offered...
    the site you provided says:

    "My units came ... with 64K of RAM installed (32K is soldered
    on the mainboard, 32K is provided by a socketed DIP-package 62256),"

    and

    "Note that for $5.90 you can buy a 628128 128Kx8 RAM chip to replace
    the 32K expansion chip;"
    http://www.futurlec.com/Memory/628128pr.shtml

    The link goes to the appropriate page at Futurlec, which still
    offers the part for $5.90, qty 1.

    James
     
  11. Kryten

    Kryten Guest

    True.

    Lewin does get up to some impressive tinkerings.

    I balked at the 13MB file size, but I still think like a guy with dial-up
    and a 100 MB disk! :)

    I have the urge to turn it into HTML but I don't think the number of
    interested readers would justify the effort. And I have other documents that
    have prior demands on my time.
    Nice. I here Digikey is the default source in the USA.

    I'm alarmed that Maplin - a hobbyist supplier - only sells this size RAM in
    surface mount. Surely they should be aiming at the hobbyist with 0.1" holed
    prototyping board?

    Strangely, the professional supplier RS Components do sell it in DIP32:
    uPD431000ACZ-70LL
     
  12. John - KD5YI

    John - KD5YI Guest


    According to DHL, the cost is $46.46 (USD) to ship them to Kuala Lumpur from
    the Dallas area of Texas (USA).

    Cheers,
    John
     
  13. Kryten

    Kryten Guest

    I hear that the Indonesian postal service is pot luck.

    If it is worth pinching they will nick it, and if it is not then they will
    just dump it. Nobody trusts them much.
     
  14. Chris Jones

    Chris Jones Guest

    I once hooked up lots of 74161 counters to cycle through the addresses, and
    built myself a 32*32 pixel graphics card using a 2102 1k*1 SRAM. Pointless
    but educational. I learnt that the adddress counters are more work to wire
    than the RAM itself. These days, I think probably the best way to count
    through the addresses is to hook up one of those shift-registers with
    feedback from an XOR gate hooked up to a couple of the bits of the shift
    register (it's in AOE as s pseudorandom bit sequence generator). The whole
    contents of the shift register would be used as the address word. The
    addresses wouldn't be accessed in the usual order but as long as you do it
    the same when reading and writing, it doesn't matter what order you use.
    The point is that you can build it with 74HC273 chips or something like
    that, rather than needing a proper synchronous counter. Also it would
    probably count a bit faster than a counter built from 74HC161s. It would
    only count through (2^N)-1 of the addresses, but in most applications one
    wouldn't be too upset to miss the very last address. As you can tell by
    the fact that I have bothered to think about this stuff, I am one of those
    people who doesn't use FPGAs yet.

    Chris
     
  15. Guest

    Guest Guest

    hi,
    could you point to some good references on dram refresh and maybe
    some circuitry to do that? you sound knowledgable on dram, maybe you
    can point me to some spec/data sheets on dram. maybe you even have an
    old pdf datasheet for an old 4meg 30pin simm you can share? or anybody
    else? I just happen to have a few dozen laying here I would like to
    use for something/anything. thanks. this is a nice group here and also
    a lot of knowledge.

    Ken


    --
     
  16. They are worth very little.
    Try putting them up on eBay.


    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  17. John - kd5yi

    John - kd5yi Guest


    Hi, Don -

    I thought it cost the seller something to do that. You published an article
    concerning the break-even cost of selling on eBay ($30,$50,?). Since they
    are worth very little (presumably << $30), then I lose money even trying to
    give them away on eBay. No thanks.

    I don't mind going to the trouble of sending them to someone who is willing
    to pay for the shipping, but that's as far as I go. This is my only effort
    to find them a loving home. After tomorrow, they can eat trash.

    John
     
  18. Guest

    Like I said, expensive for something with a total worth of around $10
    (USD). Old motherboards are not hard to come by in my line of work.
     
  19. Guest

    A bit of both. The CPUs themselves rarely gets built due to the
    complexity (number of wirewraps & amount of soldering) of their design.
    Most of my CPU design are merely simulated on Digital Works. Just
    knowing that i've implemented a working schematic and not just Verilog
    or VHDL is good enough for me.

    Microprocessor projects are built more often. Usually test jigs such as
    function and pulse generators for testing the performance of stuff I
    design profesionally.

    I'm currently building a CPU based on a Transport Triggered
    Architecture. Since it is nothing more than a glorified bus it is easy
    to build. And I can implement each functional unit on a separate
    veroboard.

    I've been planning to do just that for five years now. Never have the
    time. Most of my early design are pen-on-paper I did during lunch hour.
    More recent designs are on the PC (Notepad) I did while waiting for
    programs to compile. So the more recent ones are easier to publish on
    the web.

    I do have a web site at slebetman.homeip.net just haven't gotten around
    to putting my designs on it yet.

    Yeah but when you're trying to figure out stuff like why the add
    instruction fetches data from the wrong register it really helps if you
    don't have to worry about refresh and can clock the circuit down to 1
    instruction per minute.
     
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