Re: Does an enhanced //e _ALWAYS_ have 80 col. support?

[salfter@salfter.diespammersdie.dyndns.org (Scott Alfter)]

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In article <8Khpd.1682$VL6.925@clgrps13>,
Craig Bower \(Bender MX\) <NOSPAMnitroacd@telusplanet.NAYSPAM.net> wrote:
>"Oliver Schmidt" <ol.sc@web.de> wrote in message 
>> 2. How do I detect that an 80 col card is actually installed? Checking
>> for the existence of the $C300 firmware seems to be wrong from what I
>> understood from your answers.
>
>Not specifically wrong, I misunderstood your original question! :)
>
>Look for specific "signature" bytes that are in the $C300 range and are
>unique to the 80-column card.  From my somewhat limited experimentation
>tonight, the old style (BIG) and new style (small) 80-Col / 64K cards
>both have the first three bytes as follows:
>
>C300- 2C 43 CE
>
>And when I check the same memory location after pulling the cards,
>I get the exact same bytes.

That happens because the 80-column firmware doesn't reside on the 80-column
card.  Take a look at what's on the card.  An extended 80-column card has
eight 64Kx1 DRAM chips (4164 or equivalent), a 3-state octal latch
(74LS374), and an octal transceiver (74LS245).  Ten bypass capacitors, two
resistors, and a two-pin header make up the rest of the parts list.  None of
those are ROMs.  The 80-column firmware in a IIe resides in the motherboard
ROMs (more specifically, the CD ROM).  As someone else already mentioned,
you need to test for the presence of auxiliary memory somewhere in text page
1 to determine if a IIe can display 80-column text.

(That's what's on the original extended 80-column card, Apple part number
820-0067-B.  Third-party workalikes and Apple's later extended 80-column
card that used two 64Kx4 DRAM chips instead of eight 64Kx1s could/will be
different.)

  _/_
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