The BCD processing was indeed a big advantage of the V20, which is why Casio used it in graphing calculators like the AFX 1.0 and 2.0.
One point about comparing to the 8087 is that the 18-digit packed BCD format the 8087 used was converted internally to binary before doing any calculations. This lost the advantage BCD has of avoiding rounding errors between decimal and binary and was no better than regular binary calculations. The V20 BCD instructions didn't have that problem.
It was a common and affordable hardware upgrade for 8088 and 8086 machines.
It's a shame we didn't see more of this - while accelerators that plugged in to CPU sockets have been made for ages, the number of CPUs like the NEC ones that are made to be compatible with and improve existing systems is small. Lots of hardware has been wasted that could've had longer lives.
I had its sibling, the V30, in an Amstrad PPC640DD luggable. I then transplanted it (before ZIF sockets, it was quite harrowing, esp. at 14-15 years old) onto a fixed PC (an Amstrad PC1640HDMD) since that one had ISA slots for a sound card, and Trakblaster required a V20/V30 or 80286 as bare minimum due to some of the instructions it used.
That PPC640DD was a fascinating device, far cleverer than people remember. Really quite forward-thinking.
Side note: my brain saw "NEC V20" and I knew what it was, but it instead took me to my memories of my NEC P30 (Pinwriter) -- a wide-carriage 24 pin dot matrix printer that was loud enough to shake the whole house, and which you configured using an amusing question-and-answer dialogue. It would print a config question, scroll the paper up so you could see it, you'd answer with the buttons, it would scroll the paper back down (no wasting!) to print the next one. At the end you had this neat little transcript of the configuration and you felt like you'd talked to an alien intelligence.
Side note 2 on the subject of forgotten Amstrad devices: my first PC was an Amstrad 3286. This was a time when Amstrad stopped making weird, slightly incompatible PCs and instead made a range of excellent, straight-down-the-line compatibles with nice cases. Just at the same time as IBM were manufacturing the (really non-standard) PS/1 at a factory not twenty miles from Amstrad's... both lost to history but that 3286 was great. I think I put a 20mb HDD in it, formatted to 32mb because of an RLL controller.
> That PPC640DD was a fascinating device, far cleverer than people remember
Indeed. Its built-in modem was my gate to the world, once I figured out which wires to connect to the phone system (it came with a british jack, utterly unknown in my country back then).
The screen was quite flimsy though - its hinges failed quite early and I had to keep it propped with some objects in the back.
And it ate batteries like crazy, but on the other hand it ran on batteries when needed! This was in 1987-88, so quite cool. I remember a journalist having a cigarette lighter socket welded on a car battery terminals, and able to work for some time with it, I wonder if I can find the original article online.
Yeah, I saw someone use one running off a car, once.
It comes from a brief period of really frantic, bonkers professional computing innovation especially in the UK -- the Cambridge Z88 launched the year before.
I own its little brother, the PPC512DD. It is in fully working condition. As I understand it, the only difference is the amount of memory (512K vs 640K) and the inbuilt modem of the 640.
At some point I'll fathom how to add an external ISA slot to it, as apparently the expansion connector is compatible.
Also, way back when the Amstrads were current, I upgraded my desktop PC 1512 with a NEC V20 (or was it a 30?) for that little bit of speed increase.
I put an NEC V20 in my Amiga 2000's A2088 BridgeBoard for a nice boost in performance, and I've recently replaced the 8MHz 8088-2 in my recent acquired Tandy 1000HX with a V20. It's a great telnet BBSing machine. I've got some pics of the Tandy and the upgrade process in a gallery:
I've a NEC V30 sitting on my desk, waiting for a chance to put it on some breadboard with some support chips so I can have a play with it. Only issue I don't know what else I need to use with it! I would use UART to comunicate with it.
Loved my V30 in my Atari ST. The fun part was that it was faster than the 68000 on bus access (3 cycles instead of 4) which allowed with some special drivers to accelerate even operations under TOS.
I worked for Cray Research in the 1980s. A lot of the CAD software for the Cray 2 ran on a Z80 based CPM machine called the Intertec Suberbrain. Then we got a bunch of PCs from ATT called the ATT 6300 (Actually made by Olivetti). We figured out that if we replaced the 8086 in the ATT 6300 with a NEC V20, we could run all the Z80 software on the ATT 6300 by putting the V20 into Z80 compatibility mode. Saved a lot of work and time for us.
I used a Superbrain way back when and it was wonderful for its time.
Laptops didn't exist. Most other computers had separate boxes (screen, CPU, keyboard, floppies) that needed to be connected together. This thing was a practical, relatively nice looking all-in-one.
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[ 3.6 ms ] story [ 51.8 ms ] threadOne point about comparing to the 8087 is that the 18-digit packed BCD format the 8087 used was converted internally to binary before doing any calculations. This lost the advantage BCD has of avoiding rounding errors between decimal and binary and was no better than regular binary calculations. The V20 BCD instructions didn't have that problem.
Wow! Didn't know that! I'm impressed there is even a VT-100-compatible terminal for it.
It's a shame we didn't see more of this - while accelerators that plugged in to CPU sockets have been made for ages, the number of CPUs like the NEC ones that are made to be compatible with and improve existing systems is small. Lots of hardware has been wasted that could've had longer lives.
Good times.
Side note: my brain saw "NEC V20" and I knew what it was, but it instead took me to my memories of my NEC P30 (Pinwriter) -- a wide-carriage 24 pin dot matrix printer that was loud enough to shake the whole house, and which you configured using an amusing question-and-answer dialogue. It would print a config question, scroll the paper up so you could see it, you'd answer with the buttons, it would scroll the paper back down (no wasting!) to print the next one. At the end you had this neat little transcript of the configuration and you felt like you'd talked to an alien intelligence.
Side note 2 on the subject of forgotten Amstrad devices: my first PC was an Amstrad 3286. This was a time when Amstrad stopped making weird, slightly incompatible PCs and instead made a range of excellent, straight-down-the-line compatibles with nice cases. Just at the same time as IBM were manufacturing the (really non-standard) PS/1 at a factory not twenty miles from Amstrad's... both lost to history but that 3286 was great. I think I put a 20mb HDD in it, formatted to 32mb because of an RLL controller.
Indeed. Its built-in modem was my gate to the world, once I figured out which wires to connect to the phone system (it came with a british jack, utterly unknown in my country back then).
The screen was quite flimsy though - its hinges failed quite early and I had to keep it propped with some objects in the back.
And it ate batteries like crazy, but on the other hand it ran on batteries when needed! This was in 1987-88, so quite cool. I remember a journalist having a cigarette lighter socket welded on a car battery terminals, and able to work for some time with it, I wonder if I can find the original article online.
It comes from a brief period of really frantic, bonkers professional computing innovation especially in the UK -- the Cambridge Z88 launched the year before.
At some point I'll fathom how to add an external ISA slot to it, as apparently the expansion connector is compatible.
Also, way back when the Amstrads were current, I upgraded my desktop PC 1512 with a NEC V20 (or was it a 30?) for that little bit of speed increase.
https://www.flickr.com/photos/blakespot/albums/7215770249469...
https://j4f.info/v20-mbc
Laptops didn't exist. Most other computers had separate boxes (screen, CPU, keyboard, floppies) that needed to be connected together. This thing was a practical, relatively nice looking all-in-one.
https://en.wikipedia.org/wiki/Intertec_Superbrain
Then the IBM PC and its clones came, and the world changed.