Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Varthall on August 20, 2003, 04:27:14 PM
-
(this question came after reading the A1200 schematics forum)
What's that connector on the first revision of the motherboard?
http://www.amiga-hardware.com/a1200mbr1abig.jpg
On the next revisions, my a1200 is among those, there are only soldering pads on the place.
It's located near the keyboard connector, aligned with the (full sized) clock connector. Does it have any purpose?
Varthall
-
I think that's an early incarnation of the clockport. The A1200 was initially designed to ship with 1Mb CHIP, so the second Mb was to be connected through that interface. Of course it still accomodated a clock, and maybe some other stuff, too.
-
Matt_H wrote:
I think that's an early incarnation of the clockport. The A1200 was initially designed to ship with 1Mb CHIP, so the second Mb was to be connected through that interface. Of course it still accomodated a clock, and maybe some other stuff, too.
So does it mean that it's a second clockport? To avoid confusion, I'm referring to that stand-alone connector, which is very close to the keyboard one, not the standard clock port, which is located at the middle of the mobo and has also some empty soldering pads on later revisions. On my mobo I had to solder pins on these pads as they were needed by the melody1200 soundcard.
Varthall
-
Varthall wrote:
So does it mean that it's a second clockport
Nope, the clockport is only the rightmost 22pins of the bottom header(P9B)
There aren`t any address,interrupt or chip select lines available to make a pseudo clockport ..
The top header(P9A) carries different signals (mainly D16-24, and the row and column strobes from the budgie chip.
As the previous poster explained, it was put there plug in another 1MB of chip ram, but for once Commodore had a good idea and shipped the 1200 with 2Mb onboard, so the top header is pretty useless.
As you`ve found out, there were several balls ups when they made the 1200.
Early machines had both sets of header pins built in, then to cut costs, they decided to only use the 22 pins needed for the clock, but sometimes they left in the wrong 22pins (on the left), othertimes they left them out completely!
-
Are we talking somehow about that strange plastic covered port, between the mouse port and the floppydrive? If not, I'm still curious; What the ... was the port i just mentioned supposed to be used for?
-
mepmepmep wrote:
Are we talking somehow about that strange plastic covered port, between the mouse port and the floppydrive? If not, I'm still curious; What the ... was the port i just mentioned supposed to be used for?
Just take a look at the picture mentioned before, its a connector similar to the one for ide drives.
That covered port you mention was simply a hole for expansions, and has been used by some SCSI add-ons for accelerator boards, like GVP and blizzard ones, and by the melody 1200 audio card. Maybe other cards used that port too.
@Doobrey:
Thanks for the info! So I guess that no one has ever tried to use that port for anything...
Varthall
-
To me, that brings up another question... probably just stupid.. but still.. Is there anyway to connect the A570 to an Amiga 1200?.. Probably not I suppose.. The A500 has one SCSI port and the 1200 has two IDE ports.. Is that correct?
-
mepmepmep wrote:
To me, that brings up another question... probably just stupid.. but still.. Is there anyway to connect the A570 to an Amiga 1200?..
I would have posted this to an other thread, anyway... The answer is no, and it doesn't makes sense, too. It's cheaper and better to add an ide cdrom, you also get a faster drive this way.
Probably not I suppose.. The A500 has one SCSI port and the 1200 has two IDE ports.. Is that correct?
The A570 has an add-on port for a scsi controller, and the A1200 has one ide port which supports two devices.
Varthall
-
mepmepmep wrote:
To me, that brings up another question... probably just stupid.. but still.. Is there anyway to connect the A570 to an Amiga 1200?.. Probably not I suppose.. The A500 has one SCSI port and the 1200 has two IDE ports.. Is that correct?
I one word no. The A500 and A1200 expansion buses are to diffrent.
-
Makes me wonder if anyone has tried sawing off CN1 and soldering in a header at CN1A... Might prove useful in a tight-space case mod :-D
-
Dr_Righteous wrote:
Makes me wonder if anyone has tried sawing off CN1 and soldering in a header at CN1A... Might prove useful in a tight-space case mod :-D
CN1? You mean the mouse port?
Varthall
-
On some of the later A1200s, the motherboard was shorter and the mouse port was connected by a short ribbon cable.
But you still need a case that takes the "full length" mobo if you want to stick an accelerator into it.
-
Doobrey wrote:
On some of the later A1200s, the motherboard was shorter and the mouse port was connected by a short ribbon cable.
But you still need a case that takes the "full length" mobo if you want to stick an accelerator into it.
Yes, that's true. But it could be anyway useful to use those CN1A pads to add a clone of the mouse port, this way you could have both the mouse and a second joystick connected :)
Varthall
-
Varthall wrote:
Yes, that's true. But it could be anyway useful to use those CN1A pads to add a clone of the mouse port, this way you could have both the mouse and a second joystick connected :)
You'd still need a way to disable the +5v and gnd lines of the port that you don't want active.. The mouse and joystick can't coexist together.