Trying to reconstruct old computers of mainland China
The 1st day, 2020.11.26
The whole thing started with the one reply tweet by Shriram Krishnamurthi:
which refers back to this tweet:
Last night I went to kongfz.com (online platform focused on old books & old stuff trading) and find a handful of related books which reminds me of a discovery I've had when in university: mainland China has designed its own minicomputers & microcomputers in the 1970s; the Cultural Revolution did not stop that. Not even normal people in mainland know that: related informations mostly stayed inside universities and faculties and leaked through university libraries nowadays. I'm well aware that DJS (which is probably an acronym of `**D**ianzi **J**i**S**uanji`, which is the pinyin for electronic computer) series exist, but I didn't know there was more. Now that I have enough money do reconstruct them, I'm gonna do it if I can get hold of the schematic design (and the police won't come after me for that).
I spent an hour or two digging through cnki.net I found little to nothing. Yes, there are lots of related stuff, but most of them are either (1) related to FORTRAN/ALGOL/assembly, or (2) related to the usage (e.g. something along the lines of "how we designed this long bridge with the help of digital computer"), and almost none of them have basic information about the architectures of the machines whatsoever. The only (at least seemingly) usable is an article which talks about emulating 041 microcomputers on DJS-130 minicomputer and includes a description of 041's internal details. I did not investigate closely, but maybe I am able to reconstruct 041 from this article already.
Yes, I still have my university ID card so I can still access the university library, but it's in Guangzhou, not Shenzhen. I'll go to the Shenzhen library this weekend so maybe - just maybe - it'll spare me the trouble of going back to Guangzhou for the manuals.
I first suspected 041 is (at least some kind of) a clone of Intel 4004/4040, but no, turns out it's different. If the article was accurate the system has 4\*(1008\*8) bits (4\*1008 bytes, which is 4032 bytes) of ROM. The 1008 part really threw me off like why on earth is it 1008 and why is it 16 less than the more familiar value 1024.
The 2nd day, 2020.11.28
(This part is written on 2020.11.29)
So I went to Shenzhen Library yesterday afternoon and found absolutely nothing. As much as fruitless-ness can go, this trip has surpassed it tenfold. The first batch of old books arrived, and none of them contained enough information to build an emulator. (I did find out **DJS** does not stand for `Dianzi JiSuanji` though; it's for `Dianzi Jisuanji Shuzi`, which is literally "electronic computer digital".)
The 3rd day, 2020.11.29
So here's a quick recap:
- There was a series of computer called the DJS series in mainland China, most of which designed and built thoughout in 1960s, 1970s and early 1980s. Two machines in the DJS series seems to be the most popular: DJS-6 and DJS-130. The former was said to be designed and built independently, the latter was said to be a clone of the Data General NOVA minicomputer.
- There seems to be other series as well. From the old ALGOL 60 books in the first batch there was at least a `709` (which is probably not the IBM 709; this machine has 48-bit words while IBM 709 has 36-bit), a `TQ-16`, and a `X-2`; from the research I did on the first day (2020.11.26) there was a `041`. None of these names make any sense to me. Some of the computers even have multiple names, e.g. DJS-6 was also called `108乙`; `乙` meaning `2nd` (Heavenly Stems )
Not even Wikipedia has any information about any of these. Oh Lord.
Now that I think about it, even if I've reconstructed the machine (either by writing emulators or by implementing with hardware), I have nothing to prove my reconstruction is correct...
The second batch (yes I bought a second batch of old books) arrived and they confirmed DJS-130 is indeed a NOVA clone, so any DJS-130 emulator will have to be a NOVA emulator as well (and vice versa maybe?) I dunno man, the NOVA emulator I found online  kinda sucks a little bit so writing another emulator may be well justified...?
Kind of a letdown for me, really. I didn't come for this, if I want a reconstruction of NOVA I probably would have not invest money in those old books... I know people have come up with their own design and that's what I'm looking for.
: Heavenly Stems
: The online NOVA emulator
A tiny status update, 2020.12.5
So I asked for help on Twitter and Zhihu (think of it as Chinese Quora), and there was like only one person who was self-proclaimed interested and would help. Oh well. I guess I'll just make a NOVA emulator.