8:23 U9 was intended for a clock IC. Below that is the clock port. C= wanted to save money, so the clock IC was not fitted, but no NICD battery either. But there was a Clock port with half the header underneath. You can plug in a clock module there. But later there were also other modules that hobbyists connected there. Another sound IC or an additional serial interface or or a 10 MBit Ethernet with RJ45. A wonder what hobbyists got into the narrow address space. Most boards for the expansion port already had a clock, so the clock port was often left free.
The NEC 16-bit chips were the OEM parts in the Rev 1 boards, and that's what I have on mine. The later A1200 rev board was redesigned to use Hitachi 8-bit chips (512K each). I guess whoever worked on this machine managed to find a Hitachi 16-bit chip, which is a nice coincidence. It would have been fun to run a ramscanner on this system, just to see what was showing up on the data bus. AmigaTestKit also supports the ability to scan memory even if Kickstart can't initialize it. Nice to see people still fixing these machines. I recapped my A1200 a couple years ago, and upon disassembly, found a nice hole in the motherboard where an SMD cap went supernova. For all I know, it might have blown way back in '93 but the machine still soldiered on anyway. It's all patched up now. 8)
Yeah, one of my A500 has a drive which works in my A1200. The other two have stand-off built into the drive, so don't fit. Many years ago when I got my A1200 I swapped them as the A1200 drive was so loud.
8:23 U9 was intended for a clock IC. Below that is the clock port. C= wanted to save money, so the clock IC was not fitted, but no NICD battery either. But there was a Clock port with half the header underneath.
You can plug in a clock module there. But later there were also other modules that hobbyists connected there. Another sound IC or an additional serial interface or or a 10 MBit Ethernet with RJ45.
A wonder what hobbyists got into the narrow address space.
Most boards for the expansion port already had a clock, so the clock port was often left free.
The NEC 16-bit chips were the OEM parts in the Rev 1 boards, and that's what I have on mine. The later A1200 rev board was redesigned to use Hitachi 8-bit chips (512K each). I guess whoever worked on this machine managed to find a Hitachi 16-bit chip, which is a nice coincidence. It would have been fun to run a ramscanner on this system, just to see what was showing up on the data bus. AmigaTestKit also supports the ability to scan memory even if Kickstart can't initialize it.
Nice to see people still fixing these machines. I recapped my A1200 a couple years ago, and upon disassembly, found a nice hole in the motherboard where an SMD cap went supernova. For all I know, it might have blown way back in '93 but the machine still soldiered on anyway. It's all patched up now. 8)
Jon, Great deep dive, thank you.
Yeah, one of my A500 has a drive which works in my A1200. The other two have stand-off built into the drive, so don't fit.
Many years ago when I got my A1200 I swapped them as the A1200 drive was so loud.