Amiga.org

Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: melott on June 23, 2005, 02:40:33 PM

Title: A3k Hack
Post by: melott on June 23, 2005, 02:40:33 PM
IIRC there was an A3k 16mhz to 25mhz hack.
I checked Aminet but didn't find anything.
Anyone know anything about this hack ?
Title: Re: A3k Hack
Post by: bloodline on June 23, 2005, 02:43:40 PM
Quote

melott wrote:
IIRC there was an A3k 16mhz to 25mhz hack.
I checked Aminet but didn't find anything.
Anyone know anything about this hack ?


I guess it is possible to use the 28Mhz clock from the ECS chipset to drive the CPU, but I wouldn't do it with the standard 030 :-)

Hmmm... maybe the CPU board in the A3K runs async to the motherboard... I don't know. /me quickly looks at amiga-harware.com :-D

-Edit- Lookie here! (http://www.amiga-hardware.com/showhardware.cgi?HARDID=222)
Title: Re: A3k Hack
Post by: Orjan on June 23, 2005, 03:39:50 PM

@melott

I seem to recall something you could do to overclock the FPU in the A3000, but not the CPU.

@bloodline

What does the A3630 have to do with anything? :-)
Title: Re: A3k Hack
Post by: Tahoe on June 23, 2005, 03:41:27 PM
The A3630 is designed for use in the A4000.
The A3000 has an onboard 68030, much like my A4000CR. Wouldn't want to overclock it though, if anything goes wrong it might fry more then just the CPU :(
Title: Re: A3k Hack
Post by: bloodline on June 23, 2005, 03:43:27 PM
Quote

Orjan wrote:
@bloodline

What does the A3630 have to do with anything? :-)


I have no idea :crazy:
Title: Re: A3k Hack
Post by: melott on June 23, 2005, 04:10:07 PM
IIRC the hack involved cutting a trace and a couple
of other minor things (I don't remember just what though).
At the time I didn't pay much attention as my A3k was a
25mhz already.
I picked up an A3k 16mhz not long ago and now I wish I
had payed more attention ;-)
Title: Re: A3k Hack
Post by: Orjan on June 23, 2005, 04:20:04 PM


Is it this one?

http://www.amiga-hardware.com/downloads/a3000fpuupgrade.jpg
Title: Re: A3k Hack
Post by: adolescent on June 23, 2005, 06:27:38 PM
You could try setting all the jumpers to their 25Mhz settings.  But, I doubt that would work.  The other option that has been mentioned is to install an A3630 with FPU.

@Orjan

That hack is for the 68882.  I don't know how the 68881 would react to such an overclock.

Title: Re: A3k Hack
Post by: patrik on June 23, 2005, 06:44:58 PM
@melott:

If your 68030 and possibly 68881/68882 can manage 25MHz, I think that the A3000 would be transformed to a 25MHz model if you replace the U104 oscillator which currently should be around 32-33MHz with a 50MHz oscillator and set all the motherboard jumpers to 25MHz position. The jumpers should be described in the A3000 User Manual (http://www.amiga-hardware.com/manuals/a3000usermanual.lha), but I think it should be J151, J152 and J851 that are affected. On later A3000 motherboards (http://amiga.resource.cx/gallery/A3000rev93.jpg) it is actually printed on the circuit board how to jumper these jumpers for 16MHz/25MHz operation.


/Patrik
Title: Re: A3k Hack
Post by: Crusher on June 23, 2005, 08:51:32 PM
I have the hack on one of my A3KD 16MHz boards. It was done when I bought it about 10 years ago and it still works, although I had to slaughter the board a bit to assist my A3KT.

Pics about 450KB big.
Here you can see that it is a 16MHz board and you see the little black patchcable. (http://img193.echo.cx/img193/2972/p62343518pb.jpg)

Here is a closeup on the "Fastmem-side" of the patchcable, you see that the component is removed from the motherboard. (http://img182.echo.cx/img182/3663/p62343525bz.jpg)

Here you see the other end of the patchcable, it's attached(leaching) to that black round(cylinder) component next to the motherboard crystal(timing). (http://img289.echo.cx/img289/6671/p62343537zq.jpg)

Final word: I don't take any responsibility if you fry your board.  :-)
Title: Re: A3k Hack
Post by: melott on June 23, 2005, 09:32:43 PM
I think the smart thing to do is just look for an A3640
card.

Just what is the difference between the 16 and 25 mhz
machines other than the speed ?