View Full Version : NEC APC - She lives... well, almost

October 23rd, 2010, 08:37 AM
Almost 12 months ago, I posted here (http://www.vintage-computer.com/vcforum/showthread.php?18044-NEC-Advanced-Personal-Computer&highlight=nec+apc) that I'd picked up an NEC APC that was in bad shape.

Well, I finally got around to obtaining a set of boot disks (thanks glitch). After cleaning the diskette drives (removing black gooey sludge that was once foam pads and cleaning the heads) I tentatively booted her up with the CP/M-86 diskette inserted. At first, the [ * ] prompt changed to [LOD] then [LER] then nothing... I'm guessing that LOD means loading and LER means load error.

Simple mistake, I'd put the drives in the opposite bays - the termination and select jumpers were still correct so I just rebooted but with the diskette in the other drive. Low and behold the prompt changed to [LOD], then [LOD C], and finally brought up the following CP/M-86 screen. Yeah...


The last line is garbage (appears the same each time I boot up) with the flashing cursor after it. As I don't have a keyboard yet, I'm stuck at this point. However, I'm going to try and mod the CP/M-86 to take input from the serial port (thanks again for the idea glitch). So, next step is to hook up the diskette drive to an old PC in order to access the files. I've even found on Dave Dunfield's (http://www.classiccmp.org/dunfield) web site an NEC APC disk image that appears to contain CP/M-86 bios source code. I'll report how I get on.


November 7th, 2010, 05:19 PM
Having ALT, GR1 or GR2 locked can cause really weird output at the CP/M prompt. I just booted my APC into CP/M-86 with those keys locked to see what would happen, and I get the CP/M boilerplate just like you do, plus three lines of garbage with a blinking cursor. IIRC, CP/M-86 loads a program for setting your locale, seemingly at random though (it often doesn't load it). That would account for the extra blinking lines. You most likely have a fully working APC!

I should be doing more with my APC soon, hopefully I can get enough terminal stuff over to it to get file transfers going. It looks like there was a version of Modem7 re-written for CP/M-86. It uses the same overlay system as Modem7, so either I can try and find an overlay for it or I can write my own (not really looking forward to learning /another/ assembly language, but oh well!).

EDIT: If I have the time/money, I also want to put a bus analyzer on the keyboard port and find out what's going down the wire. It might be possible to build a PS2 <-> APC keyboard converter.

November 10th, 2010, 02:38 PM
I'm guessing that the lack of keyboard is causing it to believe ALT, GR1 and GR2 are locked. It may be something I can bypass once I've got a copy of the BIOS code in a readable format. Just need to find time to create a suitable cable and get hold of a 24v power supply to be able to hook up one of the 8" disk drives to an old PC.

Let me know if you want/need a hand with x86 coding for a Modem7 overlay. I'm probably very rusty with x86 coding, but it was my bread-and-butter some 15+ years ago.

Never used a bus analyzer, so not sure what's required, but it sound interesting. I'm hoping that once I've got a copy of the NEC APC CP/M-86 BIOS source code I should be able to work out how it communicates with the keyboard. I read with interest of a project that produced an S100 card to allow vintage systems to use a PS2 keyboard in place of a parallel attached keyboard - link here -> http://www.vintage-computer.com/vcforum/content.php?124-An-S-100-Board-to-convert-IBM-PC-keyboard-data-to-parallel-ASCII
Obviously this wouldn't work in the NEC APC as it doesn't use an S100 bus. If I had a better understanding of electronics and more info on the NEC APC bus, I'd certainly have a go at building a keyboard converter.

November 10th, 2010, 03:44 PM
You may want to check around for information on the NEC PC 9801 keyboard interface. The APC was NEC's business products section of the 9801. I believe that, at least in the basic hardware aspects, the machines are the same.

And there's lots of information in Japan about the 9801.