Why do programmers have 10 pins and Arduino have 6

[RandallR]

I have been looking at programmer boards.  The cheap one that plug in to a USB port.  Programmers like USBasp and USB ISP have a 10 pin DIP header on the end.  However the Arduinos have a 6 pin ICSP header on them.  What is the reason for the difference?  Is there some sort of AVR standard that Arduino doesn't follow?

[RuggedCircuits]

My guess is those programmers are intended to be compatible with "old style" ICSP programmers, like the original STK-500 Atmel development kits. The original ICSP connector was indeed 10 pins, and then they shrunk it down to the now-common 6-pin format.

If that is the case, the USBasp and USB ISP are oooooooolllddddd!!!

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The Flexible MIDI Shield: MIDI IN/OUT, stacking headers, your choice of I/O pins

[nickgammon]

Judging by this page:

http://www.batsocks.co.uk/readme/isp_headers.htm

The 10 pins ones have 3 more ground connections and 1 unused.

[RandallR]

In the old days you would ground one side like that so you would have a ground line every other line in you ribbon cable.  I wouldn't think "cross-talk" would be a problem in this application.

[udoklein]

The 10 pin connectors are old. The 6 pin connectors are new. I have not encountered any 10 pin device but some programmers in the last several years. Obviously 6 pin devices are slightly cheaper to manufacture. The question is why there are still 10 pin programmers out there.

[kalle123]

Those adapters come in handy

http://www.ebay.de/itm/10-Pin-to-Standard-6-Pin-Adapter-Board-For-ATMEL-AVRISP-USBASP-STK500-Convert-/280766897973?pt=AU_B_I_Electrical_Test_Equipment&hash=item415f02df35