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 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=-1&storeId=10001&catalogId=10001&productId=40011&;

Is that a good source for EPROMs?

Thanks again for all the info. I've been wanting to be able to do this
for quite some time. Just never got around to asking for help.

Best!

ATF