Question about Apple //e 80COl + 64kb card

Enabling/disabling double hires mode. AFAIK, the original IIe Rev A (that doesn't support double hires) needs that jumper open, or it won't boot. 

nick3092 wrote:

Enabling/disabling double hires mode. AFAIK, the original IIe Rev A (that doesn't support double hires) needs that jumper open, or it won't boot. 

This is correct on a Rev B or newer board removing the jumper won't make any apparent difference until you try to go to the double resolution modes...  then it won't work.  But for most other software no effect will be noticeable.  So always have the jumper on unless it is a Rev A motherboard.  Those are pretty rare because they didn't make a lot of them and most people opted for the free upgrade.

All Rev A came with the white letter keyboards but only the first ones were Rev A.  There weren't that many made.  They sold a lot more with the white letters that were Rev B. when shipped, and like I said, most people with Rev A originally got the upgrade, so Rev A are fairly rare now.  Still not rare enough to be valuable though.  Partially because Rev B is better though.

Macintosh_nik wrote:

I've been cloning this card as a training for CAD programs, so that's why the question about this jumper came up. Thanks!

The jumper inadvertently reflects a series of small blunders inside Apple Computer in late 1982:

• In the initial Rev. A motherboard, Apple initially assigned pin 50 at the AUX slot to the  ENFIRM signal, which could enable/disable the motherboard firmware.  Apple realized it was a blunder to enable so many competing functions for the AUX slot, so the ENFIRM feature was only present in the Rev A motherboard and wasn't used in any peripherals.
• In the Rev. B motherboard Apple reassigned pin 50 as FRCTXT, which forces the graphics-mode pixel clock to run at the clock speed of the currently selected text-mode.  That allowed the AN3 signal to double the HGR graphics resolution (plus a few undocumented video modes).  But the reassignment of  ENFIRM  exposed a blunder in the Rev. A motherboard: regardless of whether  FRCTXT  was implemented as active-high or active-low, it would always disable the Rev. A motherboard firmware at some point during power-up.  So it was necessary to include jumper J1 on the Extended 80-Column Card  to simply disconnect ENFIRM if the card was plugged into a Rev. A motherboard.  (When Apple produced a smaller version of the card, using 64x4 DRAMs, jumper J1 was replaced with a cuttable "bowtie" labeled AX1.)
• Outside of Apple, Applied Engineering hurried to extend RAM cards beyond 64K while the AUX slot specifications were still being revised, which spawned three revisions of their Memory Master RAM card -- all of which got it wrong.  The first batch of Memory Master cards was so terrible that Applied Engineering sold it off in early 1983 as an extra-cheap 64K card with eight spare DIP16 sockets left empty!

All the computers of the day had at least "quirks".  The original TRS-80 model 1 for example had a really terrible keyboard design and was prone to connection issues.  The build quality and materials they used in those was really very awful.  But in general just about anything made in those days there were multiple revisions of boards early on and it was not uncommon to see boards with bodge wires on them and sometimes even more extensive rework.

For what it's worth, I found some speciments of Applied Engineering's 1983 AUX slot cards:

First a picture of the prosaic AE IIe 80 Column+64K RAM card, whose equivalent of J1 is labeled with the actual slot signal names ENFIRM and AN3 as Apple had designated them in the pre-release Rev A schematics for the Apple //e.

AE with ENFIRM front.png

Here's the back side of that card, in case you want to trace out the circuits (click to enlarge):

AE with ENFIRM back.jpg

Secondly, pictured below is one problematic variant of Applied Engineering Memory Master IIe which attempted to expand beyond 64K, but erroneously omitted the C07x connection to switch between memory banks.  As a clumsy workaround, this one included a jumper that permitted the user to choose whether to support either 128K RAM or double-hires graphics.  But not both!

s-l1600 Memory Master 1.png

Additional views of that Memory Master card (click to enlarge): 

s-l1600 Memory Master 1.jpg

s-l1600 Memory Master 2.jpg

s-l1600 Memory Master 3.jpg

s-l1600 Memory Master 4.jpg

s-l1600 Memory Master 5.jpg