Recent content by Chuck(G)

I'm not clear what a PCJR (looks like a CDC drive) has to do with Commodore 1541 MItsumi. Anyone care to explain it to me.

Let's also not forget the Intel P21464 or the Hyundai HY53C464

You're right--C is plastic, D is ceramic, at least for NEC: https://www.oguchi-rd.com/PC9801/416/416%20Datasheet.pdf

NEC, AFAIK has always used the "D" suffix for plastic DIP and "C" for ceramic. Goes all the way back at least to the µPD416 chips. For 4164 chips, please consult https://minuszerodegrees.net/memory/4164.htm The 464 chips can be all over the place, particularly in terms of refresh protocol...

FWIW, I still have several hundred duplicator-grade NOS DD 5.25" floppies all bagged. Would I trust them with valuable data today? Am I crazy? On the other hand, I've had good luck with NOS 8" ones.

The blotches are mostly fungus feasting on the lubricant (fatty acids) that these things were coated with. I've got floppies dating well into the early 70s that read fine, but care has gone into their preservation. You can try to revitalize some by baking them a 58C down to 10% RH for a few...

Would it be fair to say that PCI-BIOS largely rendered ABIOS obsolete, as it supports 32-bit mode?

Well, except for the 7vpp, it doesn't look too bad, but there appears to be quite a bit of undershoot (<0v) How's your termination? The RDATA looks like MFM--sort of. There shouldn't be big gaps between pulses. Pulses should occur at intervals of t, 1.5t and 2t. In other words, looking...

Should I look at my 8" stash? I have some CCS floppies there, just don't remember which model.

360 RPM would require a high-density 5.25" floppy disk; 300 RPM for DD. The DD and HD disks are not interchangeable--the magnetic coating properties are too different. The RPM test in IMD attempts to read a single sector repeatedly to calculate the disk speed. So a properly-formatted disk...

I'll amplify a bit. In your photo note the "notch" in the edge connector as well as the notation '"2" nearby. This indicates that the visible edge connections, starting at the top are pin 2, 4, 6....34. Pin 8 is the index signal. You can figure out the rest from your attached chart. Floppy...

Format has to see an index pulse to operate. Have you checked the INDEX/ line (pin 8) to see if it's pulsing? That's where I'd start.

As I mentioned earlier, there is considerable variation between Teac drives of the same base model number. Sometimes, with a bit of probing, you can see where a jumper has been replaced with a PCB trace. I used to modify the 235HF 3½" drives for 360 RPM operation, but there were so many...

Ken Shirriff has a nice couple of pages on the workings of the 029 and 026. Worth seeking them out, as they're similarly-functional mechanical nightmares, as most IBM equipment of the era. Fun is finding the only keypunch available is an 024 (non-printing) and having to multipunch many...

When deciding between the APC, and the 5150. I considered that for the bucks, the APC was a far better machine, technically, but was unlikely to gain the momentum of IBM and the 5150--and one could buy technical documentation for the 5150 for a measly $99. NEC was a closed platform. Still...