The N23 name comes from this machine's model type 5523. It was the second generation PS/55 Note (the 55xx series in Japan being similar to the Western PS/2 series). The first generation PS/55 Note came as two seperate boards in a sandwich configuration and thus didn't have room for both a floppy drive AND a hard drive, so you picked either as an option. The motherboard has the same EXCEL codename as the N33 16Mhz.
| Model | IBM PS/55 note N23 SX |
| Machine Types | 5523-SCx |
| Release Timeframe | Sold from April 1991 for around 4 years. |
| Preceded by | Original 5523/12Mhz PS/55 note. |
| Superceded by | N33 SX (Westernised N23 SX) and then C23V (Colour version) and N51 (true MCA successor) |
| Motherboard Specs | 16Mhz 80386 CPU, 2Mb RAM on-board |
| Display Specs | 9.5" 16-greyscale VGA LCD (640x480) |
Side Note: Originally 5523 type was for the Notebook models and 5535 type was for Laptop models of the 55 Series.
The PS/55 N23 SX is a very close Japanese relative to the Western 16Mhz N33, although the Japanese N23SX is better because it had both the FDD and HDD built in. I theorise that as the 12Mhz PS/55 Note & N33 could not fit a both as HDD and FDD inside due to the two-part mainboards, so it had to have an external floppy The N33 16Mhz had it's floppy drive deleted to align both N33 machines so that both only had an external floppy connector. Although one could argue that having an internal floppy along with faster 16Mhz 386 and external video could have been a greater selling feature for the more powerful N33.
Some might consider this machine 'one' of the grandfathers of the IBM Thinkpad 700C due to it's dark case, bento-box form factor and 'nice' (but not quite brilliant) keyboard.
My one had the same blown cylinder fuse, as was inside my N33 16Mhz. After replacing this, it boots fine (with the battery pulled out). However it has no LCD.
Here is a picture of the inside, which, apart from the floppy drive is very similar to the 16Mhz N33:
And with the floppy drive and insulation moved to one side:
Here is a picture of the internal floppy drive - missing from the N33 models:
My machine doesn't boot at the moment because I cannot find the correct reference disk.
Memory
I've covered how to easily upgrade the memory in these machines if you can find any generic 72-pin Parity RAM at 70 or 80ns here.
CMOS
You need a working external floppy drive (with 23mm connector) and a bootable PS/note option disk to setup the machine with the right time and configure some necessary bits like the internal hard drive. I have noticed that replacing the CMOS battery with every kind available does not retain the settings beyond perhaps 1 hour. I have double checked this across various PS note machines and batteries and I've checked the voltage all the way back to the pins inside the motherboard and whilst the CMOS battery retains power to the CMOS, the settings invariably get lost. So my conclusion is that a) there is no point trying to replace the CMOS, b) You need a working floppy disk and drive to make the machine usable (otherwise it just sits on a 161/163 error) and c) if the day comes where it won't even retain it's setup on a soft boot, the notes will become entirely unsusable.