ridiculous looking MOSTEK 38P70 microcontroller with pigybacking EPROM from 81

[dentaku]

I found an ancient General Instruments satellite box sitting on the sidewalk so I picked it up hoping to find some interesting 4000 series logic and luckily it had three 4051B in it and a bunch of other useful stuff like a 2.5K pot (I was looking for one of those) plus some nice power supply components.
The enclosure weighs 10 pounds empty! It's obviously used as a giant heatsink. I can't find any information on this receiver but it's made by Electrohome Canada and built like a tank.

Anyway... The strangest thing I found was a MOSTEK 38P70 with a MCM2532L60 EPROM attached on top of it.
It's amazing they would use this in a commercial product considering it was more suited for prototyping.
http://eda360insider.wordpress.com/2011/11/09/3d-thursday-early-steve%E2%80%99s-improbable-history-of-3d-ics-six-decades-of-3d-electronic-packaging/

Did any of you ever use something like this in the early 80's?

Here's a link to some more photos.
http://1drv.ms/1hdVQuU

[SeanB]

Probably was an early production model where they were refining the firmware, so wanted to be able to upgrade ( in the days before reliable and cheap flash) easily in field. Later ones probably had a OTP chip instead, with a stable firmware. Other alternative is that they produced so few of these that having the OTP chip was too expensive, or it was an upgrade for only a few receivers only for a specific satellite.

[dentaku]

I'd love to find out how stupidly expensive this hardware was in 1981 in the days of giant dishes that turned with motors.
People a bit younger than me usually don't remember those.

Considering this is from Electrohome Canada it's making it even more difficult to find any information about it. I'm just going to rip parts from I anyway.

[chicken]

PoP 1.0 I suppose :-)
http://en.wikipedia.org/wiki/Package_on_package

[dentaku]

Yup, pop 1.0 and probably hand built too. I'm assuming someone hand soldered those round machine pins.
 

PoP 1.0 I suppose :-)
http://en.wikipedia.org/wiki/Package_on_package

[dentaku]

By the way, I wonder why the "first IF amplifier" board with the huge metal shielding seems to be so empty. Looking at the back of it there are only a few solder points sticking out for what looks like trimmer caps but that's it.
https://7lsvrq.by3302.livefilestore.com/y2mG-hld-cmA3fDNrhIFHfj0bQZ_oqwyuj4PZrzel0uCjK1jUHmRBAbIDq6g2EVSutdpKfOz3qElDznLk46fI4j01a7DYc9qd9DC63tlpZgkSa9dAIQ1FxxEVwfYL4ioQVO/IMG_5711.JPG?psid=1

[Kjelt]

Ridiculous? Beautifull all that gold and the ceramic package, brings back a lot of fond memories. 
Sometimes these packages are the first prototypes for some microcontroller generation and used for prototyping (debugging) but in this specific Mostek case it was a real product they sold (you can find the pdf online).
As someone above already mentioned the reasons are:
in those days there were no over the air firmware upgrades.
If you are a manufacturer and you created a new rather expensive product that operates with new (changing) standards as in the video industry that could and would change over time (other requirements, new features) you want to be able to change/replace the software accordingly. The 3870 without piggyback eprom had only OTP prom so not update was possible.
This was the time the consumer would still bring his expensive electronics device to the service departments and get it updated/repaired, not the times we are living in now and there are no such departments and the store tells you "buy a new one this is already 2 years old" 
What easier for a service department to just have new software eproms in stock and to exchange the piggyback eprom with the new one and return the device to the still waiting consumer?
Eproms in stock can be erased and reprogrammed, preprogrammed microcontrollers can be thrown away. In those days microcontrollers were not as cheap as nowadays.

I saw these kind of chips also in the first produced laserdisc players from Philips, then still called VLP video long players.
They also had these microcontrollers and it was a blessing for the hobbieist to be able to save the firmware and replace it every 20 to 30 years otherwise there would not have been a single working device anymore.
When massproduction started a year later and the product had proofed itself they were replaced with the cheaper OTP versions.

[PA0PBZ]

By the way, I wonder why the "first IF amplifier" board with the huge metal shielding seems to be so empty. Looking at the back of it there are only a few solder points sticking out for what looks like trimmer caps but that's it.

I think the rest is surface mount on the top.

[dentaku]

I guess I'll have to unsolder the shielding and see what's in there.

By the way, I wonder why the "first IF amplifier" board with the huge metal shielding seems to be so empty. Looking at the back of it there are only a few solder points sticking out for what looks like trimmer caps but that's it.

I think the rest is surface mount on the top.