treellama
Well-known member
Recently I acquired a Performa 640 CD DOS Compatible, after not owning a 68k mac for over a decade. I got it set up, put 8.1 on it because that's what I had handy. Felt really slow, like, were 68040s really this slow? You can see windows draw piece by piece.
Started system profiler, it says it's a 20 Mhz 68LC040...huh? Eventually I burned a system 7.5 restore disc and after some false starts managed to get TattleTech and Speedometer on it. TattleTech says I have a MC68040 with a 33 MHz bus running at 7.09 MHz (1772). Speedometer benchmarks put it about 1/8 as fast as a Quadra 605. Markings on the chip are XC68LC040 at 33 Mhz as expected. So, what would cause a 68040 to run slower than its bus speed? Have any of you seen anything like this before? I assume the ROM sets up the clocks
What I have tried:
- Replaced the fan. (I didn't even know it had a fan until after some disassembly I saw it in there, not spinning. So I don't know how long it has cooked itself in the previous owner's possession)
- Resetting PRAM (which is really just disconnecting power, the PRAM battery is dead)
- Removing RAM, reinstalling OS, etc.
What I have not tried yet:
- Replacing the dead PRAM battery. Waiting for a 3-AAA holder to arrive
- Taking the DOS compatibility card out
- Replacing the logic board caps
- Replacing the 68LC040. I do plan to put a full 68040 in it, but I was hoping to verify the logic board works correctly before I buy one, they're getting pricey
- Measuring the clock output with a scope. I'd have to haul one home from work, and figure out how to run the logic board on the bench
- 40 Mhz resistor mod. Only after I get everything else working, and even then, I hate surface mount tiny thing soldering.
Any ideas?
Started system profiler, it says it's a 20 Mhz 68LC040...huh? Eventually I burned a system 7.5 restore disc and after some false starts managed to get TattleTech and Speedometer on it. TattleTech says I have a MC68040 with a 33 MHz bus running at 7.09 MHz (1772). Speedometer benchmarks put it about 1/8 as fast as a Quadra 605. Markings on the chip are XC68LC040 at 33 Mhz as expected. So, what would cause a 68040 to run slower than its bus speed? Have any of you seen anything like this before? I assume the ROM sets up the clocks
What I have tried:
- Replaced the fan. (I didn't even know it had a fan until after some disassembly I saw it in there, not spinning. So I don't know how long it has cooked itself in the previous owner's possession)
- Resetting PRAM (which is really just disconnecting power, the PRAM battery is dead)
- Removing RAM, reinstalling OS, etc.
What I have not tried yet:
- Replacing the dead PRAM battery. Waiting for a 3-AAA holder to arrive
- Taking the DOS compatibility card out
- Replacing the logic board caps
- Replacing the 68LC040. I do plan to put a full 68040 in it, but I was hoping to verify the logic board works correctly before I buy one, they're getting pricey
- Measuring the clock output with a scope. I'd have to haul one home from work, and figure out how to run the logic board on the bench
- 40 Mhz resistor mod. Only after I get everything else working, and even then, I hate surface mount tiny thing soldering.
Any ideas?