It will be exciting to have a clean copy, but now I'm also realizing that
you are talking about the Technical *Manual*
<https://www.web8201.net/Files/LIBRARY_web8201/NEC8201A-TechRef.pdf>, not
the Technical <https://www.1000bit.it/support/manuali/manuali.asp?id=115>*Notes
<https://www.1000bit.it/support/manuali/manuali.asp?id=115>.* The document
for the PC-8201 that I find the most intriguing (and least legible) is the
Notes, which has this table of contents:
[image: contents.png]
What's so interesting about the Technical Notes? Well, for one it actually
defines the Floating Point notation, which I needed to document the
PC-8201's .BA file format. (Unlike all other Model T's, the computers from
NEC stored numbers in BASIC programs as binary instead of ASCII). Another
thing is that the Technical Notes is the mysterious "another manual"
referred to by the Technical Manual when it says,
NOTE: The another technical manual for PC-8201A has
> been available already. There are many information
> about the RAM file handling routines in ROM #0 in it.
> For example, •oPEN RAM FILES", 'KILL ASCII FILE",
> 'READ A CHARACTER FROM A RAM FILE' and 'CLOSE ALL
> FILES'. If you will use your application or
> subroutine with ROM #0, you had better refer to that
> manual.
The *Technical Notes* also has other interesting historical curiosities.
For example there's a page that says,
File: [MasahiroN.Docs.PPC]PPCInfo.Doc
Mathematical Routines in PC-8201 ROM
Draft 1.0
May 27, 1983
The filename makes me wonder if the internal product name for the PC-8201
was "Portable PC". Also, was there ever a non-draft version released?
Perhaps in Japanese?
Another thing it has been useful for: I had been having trouble with the
calculations in my NEC SuperROM spreadsheet tests going awry. Gary told me
that NEC's wacky math was likely due to backwards compatibility. I think he
was right as, in the Technical Notes, Masahiro specified that the PC-8201's
floating point notation was to be "EXACTLY" the same as on the PC-8000 from
1979. What I don't get yet is that I don't see anything inherently wrong
with NEC's format. It can theoretically represent numbers with 16 times
more precision than your standard 64-bit double, with a tradeoff of having
thousands of times less range. (See notes at end.) So, now I'm curious if
the weird mathematical curiosities are due to speed optimizations specific
to the PC-8201 or if the PC-8000 and PC-8800 also do strange things like
this:
DEFDBL X : X=10^2 : ?X
99.99999237060547
Have you ever seen 10² calculated with such precision before?
—b9
P.S. Notes to make my hand waving about floats more real:
A floating point value equals ±(1+f)·2ⁿ, where f is fractional (or
mantissa) part and n is the exponent.
IEEE-754 8-byte float
63 62 52 51 0
|-------------------------------------------------.
|s| 11 bits |msb 52 bit mantissa lsb|
`-------------------------------------------------'
| | `---------------- mantissa
| `-------------------------------- biased exponent (3FFh)
`------------------------------------- sign bit
NEC PC-8000 double precision float
63 62 56 55 0
|-------------------------------------------------.
|s| 7 bits |msb 56 bit mantissa lsb|
`-------------------------------------------------'
| | `---------------- mantissa
| `---------------------------------- biased exponent (80h)
`------------------------------------- sign bit
On Fri, Oct 9, 2026 at 10:37 AM Kurt McCullum <[email protected]> wrote:
> No, it's all white original paper. Lots of fold outs in there. Looks like
> I have a second copy of those sheets as well so I should be able to get you
> some good scans.
>
> Kurt
>
> On Fri, Oct 9, 2026, at 12:33 PM, B 9 wrote:
>
> No rush, Kurt.
>
> Is the Green NEC book the one with about 200 pages of which the last half
> appears to have been printed on tractor-feed greenbar paper
> <https://www.pdp8online.com/images/greenbar.shtml>?
>
> I've been trying to figure out the puzzle pieces from different poor
> quality scans like they're the dead sea scrolls for years. Just last week I
> had been talking with Gary about the mathematical routines in the ROMs
> which lead me back to the second half of the PC-8200 Technical Notes. Even
> the parts which aren't missing are very hard to read. I tried to merge the
> scans into a more legible PDF to upload to archive.org, but gave up. I
> finally decided it would be less of a pain to just retype the whole thing.
> I was seriously considering doing that and was reading up on Leiden
> bracket notation <https://papyri.info/docs/leiden_plus#leiden-conventions>
> so I could properly emend the lacunae
> <https://arxiv.org/html/2407.00250v1>. A good quality scan will save me
> so much time and effort!
>
> —b9
>
> On Fri, Oct 9, 2026 at 8:48 AM Kurt McCullum <[email protected]> wrote:
>
>
> I can do that. The only problem will be with the pages that unfold to show
> circuit diagrams but I will figure that out. Might take a couple days
> though. This weekend is rather busy for me.
>
> Kurt
>
> On Fri, Oct 9, 2026, at 10:23 AM, B 9 wrote:
>
> Kurt, if you could scan the original, it would be great! I've been trying
> to merge and decipher the two (and a half) versions of the tech ref I've
> found online and it is nigh impossible. The quality is just too poor.
>
> —b9
>
> On Fri, Oct 9, 2026 at 6:30 AM Kurt McCullum <[email protected]> wrote:
>
>
> I have two version of the Tech ref. One is a photocopy and the other an
> original hard copy in the green NEC folder.
>
> I can check those for any content you might need.
>
> Kurt
> On Fri, Oct 9, 2026, at 7:24 AM, Gary Weber wrote:
>
> Hi John,
> I may have a different PDF available. What's the missing content? Are
> you missing whole pages or diagrams?
>
> Have a look at https://www.web8201.net/tech.asp and see if the second
> document you're referencing is present.
>
> On Thu, Oct 8, 2026 at 8:58 PM John R. Hogerhuis <[email protected]> wrote:
>
> Is there only one PDF version of the 8201A tech ref? It has some missing
> content.
>
> Also the document refers to another tech ref that covers the file system
> in even more detail, don't know if anyone has found that.
>
> I ripped a version of it into an .md file so my local AI rig can utilize
> it. Unfortunately converting it to .md (marksown) leaves a lot to be
> desired... the ASCII art is mangled and the embedded OCR'd text is riddled
> with errors.
>
> If anyone has got a better copy or one with better OCR that would be
> helpful. Successfully converted to .md would be even better.'
>
> Next I'll be looking for or creating similar documents .md Inside the
> Model 100 and Hidden Secrets, the user manual and Lien's book to feed into
> the AI spaghetti flinger.
>
> -- John.
>
>
