Searching for NEC PC-8001A software & hardware

[seat safety switch]

For a couple reasons, I think my first PC-80S31 intelligent disk drive unit has a slightly bunk motherboard, so it's joined the repair pile. I got a PC-8031-2W from Japan – it took awhile to get here and I had to make another cable for it.



After a quick smoke test and some time with the air compressor to blow out some spiders, I've determined it still needs its full-height drives cleaned, greased, and otherwise maintained (they're rusty,) so it's rocking a tested half-height from the PC-80S31 for now.



Upshot is: I can say that the PC-8001 is at least loading S-DOS through my PC-8033 clone interface.



Hopefully I can get some more time to test this in the week upcoming. For now, I would say that my knockoff PC-8033 interface should at least work with the PC-8031-2W. I'll update the readme on the github page with some build instructions.

 

[voidstar78]

Folks in the house were complaining about the ancient PC speaker being too loud (and as it vibrates through the case, it kind of really is -- the IBM 5150 has a similar issue, you can't start the system up silently as it starts to loudly BEEP during the RAM checks on startup).

I didn't want to wire in a full volume control (but I thought about it, since the speaker is over a grill and we could just dangle the wires down through that) - instead, I used a different approach to dial down the internal speaker of the PC-8001 mk 2.

 

[bruce7491]

Hi guys

I'm still trying to create the floppy disks
I got the d88 dumps
these are dumps for 2s2d floppy disks
my nec pc-8031 drive is in 1s2d
I have 5"1/4 1s2d floppy disks
if I use a greaseweazle connected directly to an 8031 drive, could I create the floppy disks ?
side 1 contains no data
or maybe use a 2s2d pc drive to write the 1s2d floppy disk

I can also delete side 1 which no data with a tools utility
or take a gotek drive with the d88 dump and copy the files on a 1s2d floppy disk into a pc drive 2s2d

thanks all

 

[seat safety switch]

You can't connect a PC/Shugart-style floppy controller directly to the 8031, it doesn't speak floppy drive on the external connectors (or at least not the 34-pin one for "FDC" – not sure about the ganged port for the third and fourth floppy drive)

You can remove the internal drives from the PC-8031 chassis and reconnect them to the Greaseweazle, but you might have to play around with jumpers for head load.

The drives in my 8031 are kinda spotty. I did eventually write up my entire ordeal with the homemade PC-8033 floppy controller, PC-80S31 and PC-8031 floppy disk drives but I still need to do maintenance on the 8031 drives and figure out why the 80S31 isn't acting right.

Greaseweazle will happily write just one side of a disk image for you if you specify

--tracks=h=0

.

 

[bruce7491]

I have the original 8033, so no problem connecting the 8001 to the 8031

as the dump is double sided, the driver having only one head the verification fails
I'm going to try to make the floppy disks with a friend's double-sided drive and the 1s2d floppy disks

 

[cjs]

...the homemade PC-8033 floppy controller, PC-80S31 and PC-8031 floppy disk drives but....

It's probably best not to call the PC-8033 a "floppy controller" since that perpetuates further the confusion about where the FDC is. I'd call it a "disk unit interface," and the PC-8031, 80S31, etc. "disk units"; the latter are what contain the floppy drive controller as well as the floppy drives themselves.

 

[jltursan]

In fact, I'm still waiting to see an external all-in-one drive controller card for the NEC....:-(

For the 8001mkII I've an internal full FDC card; but I've never tested it, it has a big 50pin centronics connector and I don't have the right cable, I need to check it to be sure. It must be used in 8" drive units.

 

[cjs]

In fact, I'm still waiting to see an external all-in-one drive controller card for the NEC....:-(

I'm not sure what you mean by that. If you're talking about a board that connects to the NEC computer disk unit interface and floppy drives, that's exactly what's in an NEC PC-8031 disk unit or similar. If you're talking about a emulated one, there are things like the SD6031.

For the 8001mkII I've an internal full FDC card; but I've never tested it, it has a big 50pin centronics connector and I don't have the right cable, I need to check it to be sure. It must be used in 8" drive units.

Yes, that's no doubt a PC-8881 FDC8 controller board, only for 8" drive units, and contains the FDC; the PC-8881 drive unit has just the drives, not the controller.

And if you're interested in selling that, please contact me! I have a PC-8881, but no controller board for it, and they're rather hard to come by these days.

 

[jltursan]

I'm not sure what you mean by that. If you're talking about a board that connects to the NEC computer disk unit interface and floppy drives, that's exactly what's in an NEC PC-8031 disk unit or similar. If you're talking about a emulated one, there are things like the SD6031.


Yes, that's no doubt a PC-8881 FDC8 controller board, only for 8" drive units, and contains the FDC; the PC-8881 drive unit has just the drives, not the controller.

And if you're interested in selling that, please contact me! I have a PC-8881, but no controller board for it, and they're rather hard to come by these days.

Oh, indeed, seems to be the PC-8881: https://electrelic.com/electrelic/node/208
I'm not going to buy 8" drives; so if it's useful for you we've a deal . I best prefer trading than selling, do you have something to offer?, it doesn't needs to be for NEC machines, I'm open to any other japanese brands...

I'm not sure what you mean by that. If you're talking about a board that connects to the NEC computer disk unit interface and floppy drives, that's exactly what's in an NEC PC-8031 disk unit or similar. If you're talking about a emulated one, there are things like the SD6031.

I mean a single PCB with interface logic, FDC and data separator all in one. Something ready to use standard floppy drives (or Gotek drives) without add-ons.
I already have an SD6031, purchased AGES ago, in fact it's assembled using and old bakelite PCB, like the one pictured in the old Nishida's page.

 

[cjs]

Oh, indeed, seems to be the PC-8881: https://electrelic.com/electrelic/node/208

Be careful there: the the PC-8881 is the drive unit; the card is the "PC-8881 FDC." If you accidently order the former instead of the latter, you'll find your shipping costs increase rather massively.

I'll PM you about a trade.

I mean a single PCB with interface logic, FDC and data separator all in one. Something ready to use standard floppy drives (or Gotek drives) without add-ons.

Yeah, that's exactly the board inside the PC-8031 and similar units. You can just swap out one or both of the floppy drives for a Gotek or two (modulo any of the usual peculiarities of FDD interfaces, such as select lines and head load and so on).

 

[jltursan]

Hehe, don't worry, I'm not looking for a 8" drive unit, no way I'm going to import such a beast!. I'm happy with my PC-8031, in fact, I've already swapped one of the 5.25" drives with a 3.5" drive; so swapping again with a Gotek should be easy peasy

 

[cjs]

I'm not sure if I've mentioned this before, but I maintain a retroabandon/pc8001-re repo on GitLab with a random assortment of ROMs, documentation, hardware information, disassemblies, and suchlike. (Oh, and it's also got an easy script to download and run a PC-8001 emulator, including starting it with your own ROM code or patches.)

Anyway, I've recently put a bit more work into my PC-8001 N-BASIC 1.10 disassembly (listing file also available), to the point where it's getting vaguely useful, so I thought I'd mention that here in case anybody's interested. In particular, I have to thank 川村清 (Kawamura Kiyoshi) for his very helpful books discussing some of the ROM routines; references to them are in the header comments in that file, including Internet archive links.

I also have a little expansion ROM test program (currently just tested in the emulator, but I'll burn a real PROM at some point soon) that gives an idea of how to build expansion ROMs, if anybody finds that interesting.

 

[jltursan]

Very nice!, thanks!. Your other repos are also a good source of information.

BASIC extension tools are really fun to implement . IIRC I've the very same exercise for the MSX to add new commands through its CALL interface.

 

[cjs]

Well, I did a bunch of hacking on my exprom1 program today and it's now turned into something useful. This expansion ROM takes over the CMD statement to give you CMD HELP (just prints a line of text to remind you of the other options), CMD HELLO (a simple program to demonstrate screen output and keyboard input, and, most usefully, CMD TMON to give you a much more powerful machine-language monitor.

The tmon setup still has issues: in particular, I'm currently using the top of the BASIC memory as work area, and that gets stomped on by BASIC itself when you return to BASIC, so you lose all your settings when you re-enter the monitor. I need a better place to put those data (about 70 bytes, including the separate monitor stack).

I could, I suppose, scoot the top of BASIC memory down a bit, but that's a pretty common place that machine language routines (and sometimes programs) want to live, which means the thing you're wanting to use to debug them probably doesn't want to have anything living there. A more promising option is to move the start of the basic "text" area (program code) up, though I'm not sure if I can do that at init time. But it's already moved a bit up from "normal" for MS-BASIC (on my 32K system it's at $8020 instead of $8000), so I'm hopeful about that.

All the rest of the Disk BASIC commands just drop to the monitor through the intentry point, which is handy for debugging and testing; see the README for more details.

If someone wants a copy of tmon built for a load from cassette or diskette or something like that, drop me a note.

Oh, I've also put a note in the README about how to run this ROM in an emulator; that's actually the only way I've been testing it so far until I get together with a friend with an EPROM burner. So even if you don't have a PC-8001, or can't burn a ROM for it, that's an easy way to play with it. If there are any issues with that, let me know.

 

[clueless_engineer (Brett)]

Hello,

I've just acquired a MKII. Is there a recommendation to replace the NiCd battery used for the calendar/clock (カレンダ時計) backup. I forgot to take a photo of it before I put the machine back together so took a screenshot from my video (swapped the JP 100VAC power supply for an AU 240VAC).

It's a 2.4V NiCd that is in surprisingly good state after 40 years still. Apologies for the dust - this was taken before I blew it all out.

After a very brief search I have found a Varta replacement, 2.4V NiMH and yes, before the pedants point it out, I know the battery chemistry and thus recharging technique is different, but NiMH is apparently all that we have today ... even when I specifically ordered advertised NiCd cells from Aliexpress, they sent me NiMH.

Happy to replace with similar NiCd, hence the question.

Thanks!

 

[jltursan]

Oops, I also have a mkII and never checked the battery, time to do it urgently!.

About batteries, I've been using NiMH since long time ago and never found any issue with them, of course, these machines are never powered on frequently or running for hours. Anyhow, I best prefer to replace the battery with coin ones, usually a CR2032 with a diode to avoid recharging.

 

[clueless_engineer (Brett)]

Ahh, a diode to prevent charging - that's a great idea! I'll have a think which way to go, thanks @jltursan!

From the documentation, it says this:

The calendar clock backup battery will be fully charged if the MKII is turned on for more than 40 continuous hours. Even if the MKII is turned on after it is fully charged, the backup battery will not lose its function. A fully charged backup battery will keep the calendar clock running for about two months even if the MKII is turned off. Even if you do not fully charge the backup battery, the calendar clock will continue to run if you turn the MKII on for about 30 minutes a day.

 

[rootboy]

Ahh, a diode to prevent charging - that's a great idea! I'll have a think which way to go, thanks @jltursan!

From the documentation, it says this:

Greetings! I have some that I bought for my Amiga 2000s that came with the diode already installed.

 

[cjs]

After a very brief search I have found a Varta replacement, 2.4V NiMH and yes, before the pedants point it out, I know the battery chemistry and thus recharging technique is different, but NiMH is apparently all that we have today ... even when I specifically ordered advertised NiCd cells from Aliexpress, they sent me NiMH.

The charging techniques for NiCd and NiMH are very similar, close enough that replacing NiCd with NiMH is pretty much invariably fine so long as standard charging techniques are used. For a bit more information and references to super-deep information on this (Linden, Reddy, Handbook of Batteries, 3rd ed. (2002)) see my notes here.

 

[cjs]

FWIW, here's a new release of 8bitdev Expansion ROM #1. Tmon improvements include entry from BASIC via the MON command, ability to enter the built-in monitor from tmon via qt1, and lots and lots of documentation improvements. (Probably best to read the docs in the archive before posting questions; much is answered there.)

Getting this into a physical machine turned out to be trickier than I thought: the sockets are wired for 2316 ROMs, which obviously are difficult to contract for these days, so 2716 EPROM adapter board it is. But the machine pins usually used with these don't go into the tiny, tiny holes on the DIP sockets NEC uses so, while I've confirmed that the ROM is readable on the machine by carefully holding down a stack of 2nd socket, adapter board, socket and EPROM, it's not stable enough to actually run things reliably. I've currently got a project going to use a DIP IDC connector to bring the socket connection out the back via a ribbon cable, where I can mount a board with ZIF socket and make changing the expansion ROM (and, who knows, maybe system ROMs) super-easy, barely an inconvenience. Links etc. are in the docs in the archive.