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Old 2017-11-03, 10:51   #1
LaurV
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Default History of Computin' - personal view...

Related to this article in Ars Technica.

And kladner's post where he forgot to give the link...

Quote:
Originally Posted by kladner View Post
Shout out to LaurV. Were you in on the digital scene when
this happened?
Quote:
What Moldovanu’s holding isn’t some hobbyist kit potentially familiar to tech tinkerers back in the states. In the mid-1980s, Romania was a poverty-stricken, Communist country. So like a handful of his fellow students with a similar undeniable passion for computing, Moldovanu soon became one of only a few dozen underground computer builders in the country. They illegally manufactured computers using parts smuggled from factories and heaps of manually soldered wires. But armed with very few resources and plenty of creativity, people like Moldovanu soon fueled an underground hardware industry that would birth some of the country’s best future tech professionals.
Well, I was "one of the few dozen" too. My toy still works of course , or at least it was able to start in 2015 when the photos were done.

What is interesting it is that this toy survived hoards of students in the campus in the eighties, nineties, who used to play LodeRunner (one of my favorites, I also designed a lot of custom screens for it, which were difficult puzzles, there was an editor available, and one could make his own screens, now is playable online, hehe, and it looks sooo old...), and other thousands of games, day after day and night after night. We had a full shelf of tapes and a quite robust Russian "Electronika 302" tape player (still working nice!) Tough keyboard, from a DAF2020 (hall sensors, no mechanical contacts), and its power supply (5V/3A with just a 220-to-5V transformer, a diode bridge from a Dacia car, a 2000uF/10V capacitor and a BM323 stabilizer IC mounted on a big aluminum lump) could be used to boil coffee in the morning.

Look to that crystal in the photo, which is knotted to the fifth EEPROM using normal sewing thread, that was because one pin was broken from its root (close to the capsule) and I had to cut around it with a cutter to release a bit of metal, to which I soldered a thin wire (I think that is not visible, the one which is visible is the other, unbroken terminal). The clock was too slow to cause problems, nowadays you can not place the crystals so far from the oscillators, as you will have thousands of problems (noises, etc).

One good anecdote, a winter at the beginning of nineties, I was not in the campus, because I went to some algorithms competition or so, and my colleagues decided to make an improvement to the power supply, which was getting really hot during playing some "new" game. Note that we were a "theoretical" faculty, we learned algorithms and programing and a lot of math at school, but no electronics. That was another branch. For me it was a hobby, but my colleagues were not in the same league. They could, however, handle elementary stuff, that everybody learns in the high school. So, the power supply for the toy had a 30 cm output wire that was supplying 5V/3A. This cable was thick and hard, and short, and always raised complaints from the gamers, because it was too short, and the power supply (a very hot and heavy cube with about 15 cm edge, due to the transformer inside, and the aluminum cooler, there was no "switching power supply" available at that time) had to be kept on the table, just behind of the computer. Not so convenient... Not convenient at all... And because it was so hot, and cooling it always was a challenge, they decided to put it on the window's sill outside, where the temperature used to drop to -20°C (tough Romanian winter) or so, to cool it down and to get rid of it from the desk.

So they worked hard to build a cable extension of about two meters, using normal electric wires. The 220V cable on the other side of the box was not a problem, as it was already long enough, 5 meters or so. They installed the power supply outside on the window (we were living at 4th floor), in a nice box, to be shielded in case it snows, and were happy thinking they made me a nice surprise for my return. They also labored to make the box, and make it nice...

But then, plug it in... Silence... The freaking beast didn't want to start at all. Take the cable out, measure the voltage, 5 Volts sharp. Polarity? The right one... What the hack... They decided to wait for me, and they were worried that the computer got damaged...

When I came back I put my hands on my had and pulled my hair...

There was nothing wrong with the computer, but the 3 amps in the over 2 meters of cable were causing a voltage drop of about 0.4V, because the Ohm law says that U=I*R, so the beast was getting only like 4.5-4.6 volts, and those TTL circuits were very sensitive to the right voltage... When they pulled the cable and measured the voltage, it was 5V because no consumption in the cable...

There was a reason why the initial cable was (and it still is) just 30 cm...

Well... fun times...
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Last fiddled with by LaurV on 2017-11-03 at 14:40
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Old 2017-11-03, 10:54   #2
LaurV
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Old 2017-11-03, 11:05   #3
LaurV
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Old 2017-11-03, 11:16   #4
Nick
 
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Impressive!
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Old 2017-11-03, 14:46   #5
kladner
 
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Quote:
Originally Posted by Nick View Post
Impressive!
Indeed! Thanks for the stories and pictures. Sorry about the "missing link."
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Old 2017-11-03, 15:23   #6
LaurV
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Quote:
Originally Posted by kladner View Post
Indeed! Thanks for the stories and pictures. Sorry about the "missing link."
No problem. I got the link a couple of times on mail and all messengers I use, before and after your post, from a couple of persons who knew me and/or my bad habits, including my SWMBO and including Xyzzy, hehe...

In some of the photos you see the RAM. Those 4 rows times 8 circuits, totally 32 pieces, were "high class" Russian stuff , RAM memories, each of them TWO KILO-BYTES. Totally 64 KB. Not mega, not giga, not tera.... KILO.

From which, only 48 could be used by the program. The first 16 were overwritten at boot time with the content of the ROM - the Basic interpreter, or the CP/M OS, depends what you had programmed into the ROM. And you could not write to them using normal procedures, they were seen like Read Only. But you could write to them if you knew how. The ROM is/are those big white lumps with a glass window on top. That is UV-erasable ROM, this means that if you want to program something else into them, then you need to erase them, i.e. you have to take them out of the sockets and put them under a strong UV lamp for half hour, to erase.

In fact, what Romanians brought new to the Sinclair Spectrum (it was not just a blind copy) was these additional 16k of RAM, which made the toy about 2 times faster than the Spectrum, and also gave the possibility to load other OS than the Spectrum's Basic. The Spectrum had also 16K of ROM (the low addresses), but only 48K of RAM (the higher addresses). To clarify: the Z80 family had only 16 address lines and therefore it could only address 2^16=64k memory totally. either RAM or ROM or whatever you could mount around it. Therefore, as the Spectrum had 16 ROM +48 RAM, the code (calls to Basic stuff, etc) was always executed from ROM directly. CoBra on the other hand, had a full 64K RAM, which was always accessed by the processor, but you could select what you use for the first 16, either some ROM page, or the RAM. You could mount up to 64 or 128 K of ROM too, that is either 4 or 8 pages of 16k each. When the computer starts, one of this ROM pages gets selected as "low 16k", which is copied in some high RAM zone, then the first 16k of RAM are selected like "low 16k", and the 16k from the high RAM is copied to the low RAM. Then, the code would only be executed from RAM. This way one could load different OSes at bootup (each programmed in its own 16k page in ROM). People who knew could do some tricks to swap pages between ROM and RAM, or even keep their favorite programs and games in ROM so they start every time without the need to be loaded from the tape (process which was extremely slow and bothersome). Later CoBra computers even had attached monitors and floppy disks and they were running CP/M native.

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Old 2017-11-03, 19:08   #7
xilman
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Quote:
Originally Posted by LaurV View Post
In some of the photos you see the RAM. Those 4 rows times 8 circuits, totally 32 pieces, were "high class" Russian stuff , RAM memories, each of them TWO KILO-BYTES. Totally 64 KB. Not mega, not giga, not tera.... KILO.

From which, only 48 could be used by the program. The first 16 were overwritten at boot time with the content of the ROM - the Basic interpreter, or the CP/M OS, depends what you had programmed into the ROM...
I'm getting all soggy with nostalgia. Back in the day, even 32K was considered a large amount. I've programmed systems with as little as 128 bytes of RAM. One of the marks of a true hacker was efficiency in using the storage available within a Z80 chip. Even I drew the line at using the DRAM refresh counter for general purpose storage but I knew people who did.
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Old 2017-11-03, 19:35   #8
chalsall
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Quote:
Originally Posted by xilman View Post
I'm getting all soggy with nostalgia. Back in the day, even 32K was considered a large amount.
Ditto, and indeed! In grade school we used to code (usually in assembly; the n00bs did BASIC) on machines with 4 KiB of RAM. But then we also used to have to walk 4 km to and from school, in the snow while it was raining, uphill in both directions...

Seriously though, the amount of storage and compute we have nowadays is just mind blowing!
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Old 2017-11-03, 19:49   #9
Batalov
 
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I feel nostalgic, too. I'd made hundreds of these boards (soldered from components), somewhat modified to perform this technical function (try google translation). I'd made multiple changes in software for those beasts, too (in Z80 asm, and then burnt into EEPROMs).

All these EEPROMs, Z80, discrete logic chips... Ah. Too many memories, too little time.
Had a UV light chamber to recycle (erase, reprogram) EEPROMs, the whole shebang...
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