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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Tahoe on April 26, 2006, 05:56:41 PM

Title: Mysterious jumper A4000T motherboard
Post by: Tahoe on April 26, 2006, 05:56:41 PM

While upgrading, fiddling and tweaking my A4000T I found jumper J700 marked "Haynie Kludge".... WHOA!
What does it do? Is this the mysterious jumper which magically pops C= back to life and the Amiga back in the saddle? Or does the mainboard just go "POOF"?

On this (http://amiga.resource.cx/photos/photo.pl?id=a4000t&file=A4000Trev4) picture you can find it right underneath the Buster (11)...

Title: Re: Mysterious jumper A4000T motherboard
Post by: Imation73 on April 26, 2006, 06:13:50 PM

Hi,
I search with google, ant this is the answer:
From the A4000 Hardware Guide, Jumpers section:

    "Haynie Kludge" Jumper (courtesy of Dave Haynie)

    "That jumper enables the "early sizing" mode on the Zorro III bus. One
    of the complaints about Zorro III is that the size of a transfer isn't
    known until the data phase of the cycle. So in the Zorro III addendum I
    added an optional mode that allows data size information to be latched in
    the address phase. Just in case any existing boards have a problem with
    this (if they go by the spec, they don't, but who really knows what
    they're doing), it's shipped disabled. The idea was to test this out in
    the A4000T, bless it as standard for future Zorro III controllers as long
    as it did what designers wanted."

Regards
Alessandro

Title: Re: Mysterious jumper A4000T motherboard
Post by: Hyperspeed on April 30, 2006, 12:39:11 AM

Q) What do you get if you cross a kangaroo with a sheep?
A) A wooly jumper

Title: Re: Mysterious jumper A4000T motherboard
Post by: TjLaZer on April 30, 2006, 05:00:22 AM

It's the Sex and Free Beer jumper!  Once jumped, Haynie himself will bring over a keg and Jenna Jamison!!  ;)

"NEVER EVER mess with a PCB jumper you don't understand, even if it's labelled "SEX AND FREE BEER".
--Dave Haynie

Actually that jumper does this:

"This jumper activates a modified type of
Zorro III cycle, a thing called "early size mode". This lets a Zorro
III cycle indicate its data transfer size at address time, rather than
waiting until data time. It should be compatible with all boards that
follow the Zorro III specs. But since we couldn't test this in
advance, it was made a jumperable option. This mode is described in
the Zorro III addendum that I wrote in April '93 or so."

Dave Haynie          | ex-Commodore Engineering | Ki No Kawa Ryu Aikido
Sr. Systems Engineer |      Class of '94        |    "Life was never
Scala Inc., US R&D   |  "See us in the movie!"  | meant to be painless"

Title: Re: Mysterious jumper A4000T motherboard
Post by: TjLaZer on April 30, 2006, 05:08:53 AM

lol

Title: Re: Mysterious jumper A4000T motherboard
Post by: Jose on April 30, 2006, 02:04:15 PM

In practice what are/would have been the advantages of this mode ? Does it allow faster transfers with existing cards ?

Title: Re: Mysterious jumper A4000T motherboard
Post by: Piru on April 30, 2006, 02:08:43 PM

@Jose

No. It gives no actual benefits.