This is a picture of the KR1818VG93, a Soviet clone of the WD1793 floppy controller. It was used in some Spectrum clones:

KR1818VG93 chip package (source)

What are the two windows in the chip package for? They appear to have test points or holes for pins in them, which go all the way through the chip to equivalent windows on the bottom side. Did the original FD1793 ever have them, or if not why did the clone have them?

  • 1
    Another listing of it: inspireuplift.com/ca/…
    – Brian
    Commented Jan 20 at 2:28
  • 4
    Technically, these “test points” are on the lead frame, connecting the pins to the actual chip, which is under the center plastic. The actual chip is not exposed.
    – DoxyLover
    Commented Jan 20 at 8:25
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    Would this have any manufacturing similarity to the 8031-derivative devices which had a 40-pin 8051-compatible lead frame pointing downward, and a 28-pin EPROM socket on top, e.g. would those devices have used a package somewhat like this to break memory bus pins to protected connection points that were off to the side, and could then in turn be connected to the socket pins on top?
    – supercat
    Commented Jan 22 at 16:07

1 Answer 1


I have multiple of these chips at home and I have seen multiple explanations for these. By the way, not only the WD1793 clone features this packaging but also many other ICs, for example the clone 8086s and 8088s, several peripherals for the 8086 and other microcontrollers.

Notably, they do not all have these test points and thus, I do not think that they were used for testing.

As far as I remember, some say that the die was initially intended for another package (e.g., flat), but because of manufacturing inaccuracies it did not fit so they put it into this package. However, I do not really believe this.

My theory is, that it is simply crude packaging techniques which were used by a specific factory. Just like western chips, eastern chips also have a "brand". In the USSR, these were usually printed on as logos. If you look on the internet you will see that almost all ICs which have this "diode" logo are packaged this way. There are certain chips which were produced by multiple factories, such as 8086 clones. And when you compare them, they all have different packaging depending on the factory that produced them. Some have normal plastic packaging like in the west. Usually, just with the part number. Those, which were intended for export have "Manufactured in the USSR" written on them. Another factory produced 8086 clones, which look like 3 small plastic blocks glued together. These are not always perfect and you can see these traces as above between the blocks.

  • JFYI the "diode" logo seems to belong to Ukrainian "KVAZAR-IC" factory (you can see the logo to the left from the factory name in Cyrillic here: radio-hobby.org/uploads/element/img/kvazar-is-01.jpg)
    – DmytroL
    Commented Jan 25 at 11:19
  • There's also a thread in Russian where these windows are being discussed: phantom.sannata.org/… Looks like the majority of the participants think those windows were required for the manufacturing process on a specific factory (because not all Soviet clones of WD1793 have them)
    – DmytroL
    Commented Jan 25 at 11:22

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