Apple II bus breakout board

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a2retro

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Feb 8, 2008, 8:58:42 PM2/8/08
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To: comp.sys.apple2
Hi,

With the current discussion of prototpye boards going on, it brought me
back to an idea I was considering ... I am planning on making a few of
these in my next batch of PCB's

http://www.a2retrosystems.com/images/lojack/a2Breakout_bare.bmp

The idea is that you would plug one end into a slot and the other end
could take a variety of 50 pin connectors that could be soldered across
the fingers.

(pictures are examples only)
std 25 x 2 male header -
http://www.imperial-connect.co.uk/products/Thumbs/A1A.gif

25 x 2 shrouded header - http://www.cadforum.cz/catalog_en/file.asp?blk=947

These first two would work well with old internal scsi cables.

std 25 x 2 female header -
http://www.hqew.com/File/DIYImg/2100/041106161546s.jpg
Use a std perf board that has a 50 pin angled header soldered to it, you
could plug that into the top of the board slot adapter.


or you could use a board edge connector like these

http://rocky.digikey.com/WebLib/CW%20Industries/Web%20photos/CWR-170-50-0003.jpg

connected to a ribbon cable.


I also placed a dual row of holes on the face of the board so that a
header could be connected out the side for logic analyzer leads or
anything else you can think of.

http://www.a2retrosystems.com/images/lojack/a2Breakout_header.bmp
or
http://www.a2retrosystems.com/images/lojack/a2Breakout_shroud.bmp

I was wondering if there was any interest in my making batch of these up
for sale.

Price would be approx $6 each or 3 for $15 (bare boards only - quality
PCB with solder mask and silk screen) - if gold fingers were required
then the price would basically be double.

Send an email to sales@a2retrosystems if you think this is something you
might be interested in.

Glenn
--- Synchronet 3.14a-Win32 NewsLink 1.85
A2Central.com - Your total source for Apple II computing.

fer...@gmx.de

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Feb 9, 2008, 12:58:57 PM2/9/08
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I'm unable to see the pictures... your server seems to be down.
Such a breakout board is a nice idea.
But I'd include buffers for all signals and fuses for the powers to
protect the Apple 2.
And I'd use a 68-pin cable where I'd put the power lines between the
high freqency signal lines:
16 address, 8 data, 3 strobes, R/W, 4 clocks and 2 interrupt signals
yield 34 pins. the other 34 should be reserved for power. This way
interference between adjacent wires is reduced allowing a longer cable
length.


---
Ferdinand

a2retro

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Feb 9, 2008, 2:51:50 PM2/9/08
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To: ferdimh
> --- Synchronet 3.14a-Win32 NewsLink 1.85

Hi ..

yes my ISP is moving server instances to new hardware this weekend ...
things should be back in awhile.

thanks for the feedback ....

I was trying to keep things simple/flexible as possible and wanted to
keep it strictly pass through .. being targeted to the folks who would
sacrifice an old disk II controller just to get an edge connector.

I see myself using the side pins to attach Analyzer leads and the top
card edge to solder a female dual row socket .... I will then use the
90deg header mounted on perf board to plug that into the female socket.
Being content to have my card under development sticking out the top of
the case.

I will give your suggestions some thought and maybe integrate them or
come up with a second version of the breakout board.

Thanks again ...

Michael J. Mahon

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Feb 9, 2008, 3:28:59 PM2/9/08
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fer...@gmx.de wrote:
> I'm unable to see the pictures... your server seems to be down.
> Such a breakout board is a nice idea.
> But I'd include buffers for all signals and fuses for the powers to
> protect the Apple 2.

Buffers are problematic for 2-way signals, and in any case
modify the electrical interface so that a card designed to
work on the other side of the buffers may not work properly
when installed directly on the Apple bus.

Best plan for prototyping is to keep any bus extension to
a few inches (like an extender card) and don't put any
extra electronics between the bus and the prototype card.

> And I'd use a 68-pin cable where I'd put the power lines between the
> high freqency signal lines:
> 16 address, 8 data, 3 strobes, R/W, 4 clocks and 2 interrupt signals
> yield 34 pins. the other 34 should be reserved for power. This way
> interference between adjacent wires is reduced allowing a longer cable
> length.

FWIW, I've successfuly operated many (not all) Apple II cards at
the end of a 50-wire ribbon cable about 30" long. No buffering or
crosstalk protection was required, and only the usual power bypassing
on the card itself.

Most cards for the Apple are amazingly robust and tolerant of
extra wire (though the disclaimer about perturbing timing and
edges with buffers above still applies in general).

-michael

NadaPong: Network game demo for Apple II computers!
Home page: http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."

sfahey

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Feb 9, 2008, 4:37:35 PM2/9/08
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To: Michael J. Mahon
On 2/9/08 2:28 PM, in article MISdnbUUSazFkDPa...@comcast.com,

"Michael J. Mahon" <mjm...@aol.com> wrote:

> FWIW, I've successfuly operated many (not all) Apple II cards at
> the end of a 50-wire ribbon cable about 30" long. No buffering or
> crosstalk protection was required, and only the usual power bypassing
> on the card itself.

Homemade version of the SCRG Extend-a-Slot?

a2retro

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Feb 9, 2008, 8:45:13 PM2/9/08
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To: ferdimh
> --- Synchronet 3.14a-Win32 NewsLink 1.85

Web site is back up ...

Glenn

Steven Hirsch

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Feb 9, 2008, 9:22:17 PM2/9/08
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sfahey wrote:
> To: Michael J. Mahon
> On 2/9/08 2:28 PM, in article MISdnbUUSazFkDPa...@comcast.com,
> "Michael J. Mahon" <mjm...@aol.com> wrote:
>
>> FWIW, I've successfuly operated many (not all) Apple II cards at
>> the end of a 50-wire ribbon cable about 30" long. No buffering or
>> crosstalk protection was required, and only the usual power bypassing
>> on the card itself.
>
> Homemade version of the SCRG Extend-a-Slot?

I have a real-life Extend-A-Slot. The only things I've found that won't work
in it are DMA disk controllers and a Transwarp IIe. Not surprising, since
these push the envelope even when plugged directly in :-).

Michael J. Mahon

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Feb 10, 2008, 1:50:44 AM2/10/08
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sfahey wrote:
> To: Michael J. Mahon
> On 2/9/08 2:28 PM, in article MISdnbUUSazFkDPa...@comcast.com,
> "Michael J. Mahon" <mjm...@aol.com> wrote:
>
>
>>FWIW, I've successfuly operated many (not all) Apple II cards at
>>the end of a 50-wire ribbon cable about 30" long. No buffering or
>>crosstalk protection was required, and only the usual power bypassing
>>on the card itself.
>
>
> Homemade version of the SCRG Extend-a-Slot?

Essentially. The cable I used was actually a surplus cable
used in an older computer system (maybe an HP3000 ;-), with
three connectors as in the Apple II, and, at the other end
a 50-pin card-edge.

About as close to an Extend-a-Slot as you can get without
switches. ;-)

I've also used an Extend-a-Slot with a printer card, a modem,
a Mockingboard, and something else I can't remember. ;-)

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