Re: UDC short mystery - 2 different cards that both hate my Apple 5 1/4" - Different revs?

["atfphotography@gmail.com" <atfphotography@gmail.com>]

On Jun 12, 6:30 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> atfphotogra...@gmail.com wrote:
> > On Jun 11, 10:30 pm, David Wilson <mcs6...@gmail.com> wrote:
> >> On Jun 12, 10:58 am, "atfphotogra...@gmail.com"
>
> >> <atfphotogra...@gmail.com> wrote:
> >>> Sweet! I'll take a look at the these. How do you actually determine
> >>> which eprom you use in each situation? I have a Liron card here that I
> >>> would love to dump the ROM and create another one. Do you count pins
> >>> (24 in this case) and then someone figure out how much memory is on
> >>> the original ROM itself?
> >> You read the part number on the chip (easy if it is an EPROM like the
> >> UDC and not covered in a large label).
>
> >> The SSC uses a 2716 with the same 256 bytes mapped into the slot CnXX
> >> space. Newer cards like the 1MB Apple "Slinky" Memory card use a 2732
> >> which allows them to have a unique copy of code for each slot.
>
> >> 24pin
> >> 2716 = 16 kbit = 2 kbyte
> >> 2732 = 32 kbit = 4 kbyte
> >> 28pin
> >> 2764 = 64 kbit = 8 kbyte (your green UDC has the CMOS version of this:
> >> 27C64)
> >> 27128 = 128 kbit = 16 kbyte
> >> 27256 = 256 kbit = 32 kbyte
> >> 27512 = 512 kbit = 64 kbyte
>
> >> If the card has a mask ROM then I tend to tell the programmer that it
> >> is the largest part with that many pins. Then I look at the contents
> >> and look for either 1/2 or 1/4 all being FF (which tells me that some
> >> of the address pins are actually chip selects) or if the dump repeats
> >> then some pins may be don't cares.
>
> > That's amazingly helpful. I'll check out the ROMs on the cards and see
> > if I can determine their model. Here comes the big question; where do
> > I get empty EPROMs of those models? I looked on Jameco and they had
> > three models of the 2716.
>
> >http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...
>
> > Is that a good source for EPROMs?
>
> If you have an EPROM eraser (and you'll need one anyway ;-), I've found
> this to be a great source of inexpensive used EPROMs:
>
> http://epromman.com/
>
> -michael
>
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>
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Nice!

Thanks for the info. Looks like I'll need one of those too.

Best!

ATF