08/06/89: 256K x 4 bit chips by Delphi, | Category: Delphi - Hardware Hacking | 5 comments - (Comments are closed)

256K x 4 bit chips

52702 6AUG89-1621 Hardware Hacking
256K x 4 bit chips

I recall you once explaining that the reason 256K x 4 bit chips could not be
used on the CoCo is because the CoCo does not support the refresh cycle needed
by these 1 megabit chips. (Wasn’t it 512-cycle vs. the normal 256-cycle)?

If this is what I think it is, there may be a way around it. If my memory is
not to rusty, there may be a way around this. When 256K upgrades first started
coming out for the Atari XL series, it was noted some of the earlier ANTIC
chips did not support the proper refresh. (In fact, I believe they mentioned
it only support 128-cycle, and 256-cycle was needed). As a result, some mods
included a circuit to provide the refresh extension.

I would expect this would work for the CoCo as well, if I have my info straight.

And with 256Kx4 chips going for as low as $15, and 256Kx1 chips going for
about $6 each, some savings could be realized even if the extra chips needed
(I believe the Atari circuit took 3) ate up the savings in power and board

BTW, I don’t plan on doing anything about this if this is possible, as I
already have a 512K upgrade. But I thought some prospective board maker out
there might be interested in if my thoughts are correct…which would mean a
256Kx4 bit chip 512K upgrade would be economically feasible.

b-back, LEM

5 comments to 256K x 4 bit chips

  • pucc_unknown

    52727 7AUG89-0144 Hardware Hacking
    RE: 256K x 4 bit chips (Re: Msg 52702)

    I’m sure there is some sneaky way to add the extra count. The
    question is… can it be done ECONOMICALLY???

    256K by 4 for $15 ??? Tell me where you saw them at that price.
    I find that VERY hard to believe. I doubt one can get them for
    less than $25 each. The Jaemco price is closer to $60.

    Note that a FEW may pop onto the surplus market… or appear
    at flea markets… for very low prices. BUT… this does
    not represent a reliable source!

    Tell me more about 256K by 4 for $15. I might be willing to buy
    a few thousand… I may be able to sell them for $30 here
    pretty quickly.


  • pucc_unknown

    52756 7AUG89-2331 Hardware Hacking
    RE: 256K x 4 bit chips (Re: Msg 52727)

    Well, let me check my latest issue of Computer Shopper. (He thumbs though over
    600 pages while the pennies drop rapidly down the black hole called Delphi…)

    Okay, here is the first IC place I found. Page 178 of the August issue, I.C.
    Express: 256Kx4, 100ns, $15.75. (lists it as a 514256). Let’s try another…

    Arrgghh, remember the name of another one, but they dont’ caryry the 256Kx4 bit
    part. Most of the best prices are found in the small ads, and are a lot harder
    to find than I.C. Express was.

    Ah..ha. Here’s another…on page 585. Unitex. 256 x 4 – 120ns, $15. (100ns from
    them is $17).

    What kind of cut do I get on the deal? .

    b-back, LEM

  • pucc_unknown

    52772 8AUG89-0426 Hardware Hacking
    RE: 256K x 4 bit chips (Re: Msg 52756)

    Hmm… amazing… I’ve not been following those prices much lately.

    Need to look at my computer shopper more often.

    Glad to see memory prices are dropping.


  • pucc_unknown

    52805 9AUG89-1947 Hardware Hacking
    RE: 256K x 4 bit chips (Re: Msg 52772)

    Computer memory is actually almost as cheap now as when I did the 256K mod to
    my Atari 1200XL years ago. A couple of weeks ago, Chip Merchant quoted me a
    price of $12.85 each for 80-ns 1 megabit DRAMs. I purchased the 150-ns 256Kbit
    chips I needed back in 1985 (or was it ’86?) for about $2.75 each.

    I saw a message on a FIDO echo recently where one person paid $11 each for
    their new 1-megabit chips.

    Too bad Tandy did not have the foresite to include 512-cycle refresh capability
    in their GIME chip. Of course, they could always revise, as Atari did when
    they took the ANTIC chip from 128-cycle to 256-cycle capability.

    BTW…that circuit the mod used for extending the refresh was pretty inexpensive
    ..just some low cost TTL chips. Maybe some century I’ll dig it out, or I’ll
    just open up my 1200XL and see what it has on the board.

    Frankly, if Tandy does come out with a CoCo 4, and it does not use a 68000,
    they had better pay serious consideration to using 256Kx4 chips for a base RAM
    of 512K.

    b-back, LEM

  • pucc_unknown

    52825 11AUG89-0336 Hardware Hacking
    RE: 256K x 4 bit chips (Re: Msg 52805)

    I agree with you about the 256K by 4 chips… they make
    much more sense for a 512K machine.