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Thread: 6 minutes snap-on 386SX to 486 upgrade "chip"

  1. #1

    Default 6 minutes snap-on 386SX to 486 upgrade "chip"

    Hey guys, what do you think about this 6 minutes snap-on 386SX to 486 upgrade "chip" I saw on an informaticaviejuna's Instagram post?

    I had no idea such a thing even existed!!! (and how in the world would it work "disabling" the 386 CPU that is left underneath since the motherboard clearly doesn't have a jumper to disable the CPU)

    https://www.instagram.com/p/Bu9oIleF..._web_copy_link

    6 minutes snap-on 386 SX to 486 upgrade chip.jpg

    I'd love to hear your thoughts about this.

    Thanks!

  2. #2
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    The Rev to 486 were fairly well known and they did work. Line it up correctly, push down so it contacts the traces to the SX chip, and it just works. There are a few threads here and elsewhere about it if you want more information.

    I don't recall if the Rev to 486 was reversible. Cutting the traces to the 386SX seems simple enough to do with the design but might be a bit more permanent than most want.

    The major drawback was the price of the upgrade was about the same as buying a new motherboard with the same improved chip. A new motherboard would be faster because of 32-bit memory and 32-bit slots.

  3. #3

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    Quote Originally Posted by krebizfan View Post
    The Rev to 486 were fairly well known and they did work. Line it up correctly, push down so it contacts the traces to the SX chip, and it just works. There are a few threads here and elsewhere about it if you want more information.

    I don't recall if the Rev to 486 was reversible. Cutting the traces to the 386SX seems simple enough to do with the design but might be a bit more permanent than most want.

    The major drawback was the price of the upgrade was about the same as buying a new motherboard with the same improved chip. A new motherboard would be faster because of 32-bit memory and 32-bit slots.

    Thanks!
    Good points! I didn't know about the price, the usual problem: money. I guess they played the marketing more about the fast and simple update compared with replacing motherboard and everything. Something like the idea of going out to your favorite computer store, buying it, getting back home, opening the case and clicking it on. Done. Like going out to buy a slice of pizza (aka poison).

  4. #4

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    Quote Originally Posted by krebizfan View Post
    The Rev to 486 were fairly well known and they did work.
    I don't know, I think they are kind of notorious for partially working.

    There are compatibility issues with FPUs, and sometimes they won't double. Sometimes the cache doesn't get along with certain devices.
    Most importantly, you need to make sure your 386SX CPU has a float pin. The ones earlier ones didn't.
    "Will the Highways on the internets become more few?"

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    Quote Originally Posted by AriesMu View Post
    ...
    I had no idea such a thing even existed!!! (and how in the world would it work "disabling" the 386 CPU that is left underneath since the motherboard clearly doesn't have a jumper to disable the CPU)
    The 386SX has a pin that allows an ON Circuit Emulator (ONCE; Intel's acronym) to disable the CPU without making any modifications to the board. This pin is call FLT for 'Float' and it does just what it says; activating this input to the 386SX floats (tri-states) all of the 386SX outputs and allows an external processor to take control. It was originally put in for the debugging capability of the ONCE device, but it also works for speedup processors.
    --
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  6. #6

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    Quote Originally Posted by lowen View Post
    The 386SX has a pin that allows an ON Circuit Emulator (ONCE; Intel's acronym) to disable the CPU without making any modifications to the board. This pin is call FLT for 'Float' and it does just what it says; activating this input to the 386SX floats (tri-states) all of the 386SX outputs and allows an external processor to take control. It was originally put in for the debugging capability of the ONCE device, but it also works for speedup processors.
    Wow interesting! It's exciting to find out those old-days buried special functions!

  7. #7

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    Quote Originally Posted by krebizfan View Post
    The major drawback was the price of the upgrade was about the same as buying a new motherboard with the same improved chip. A new motherboard would be faster because of 32-bit memory and 32-bit slots.
    Hence why the marketing showed a non-standard motherboard equipped machine (a PS/2) that cost a ton when it was new. It was ALOT cheaper for a business with a ton of machines to buy these and install vs. getting something new at the time. Also a slight chuckle about the Windows in 386 Enhanced Mode bit...... the 386 could already do that!

  8. #8

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    "Increases CPU benchmark performance up to 130%"

    Yes, I believe in such increase in benchmarks, but not in real-world applications.
    Most of the difference between 386SX and 486SLC was that the latter had some internal cache, so tiny benchmark code ran completely within the cache, ie. very fast.
    Larger programs had to live in the main memory, accessible via the narrow 16-bit bus, so the speedup wasn't that great.

  9. #9

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    Quote Originally Posted by njroadfan View Post
    Hence why the marketing showed a non-standard motherboard equipped machine (a PS/2) that cost a ton when it was new. It was ALOT cheaper for a business with a ton of machines to buy these and install vs. getting something new at the time. Also a slight chuckle about the Windows in 386 Enhanced Mode bit...... the 386 could already do that!
    I think they were just being lazy. This company also made 286 to 486 upgrade modules that used the same chip. They probably shared advertising material for these two products and forgot to remove that line in the 386 to advert.
    "Will the Highways on the internets become more few?"

    V'Ger XT

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    Quote Originally Posted by Anonymous Coward View Post
    I think they were just being lazy. This company also made 286 to 486 upgrade modules that used the same chip. They probably shared advertising material for these two products and forgot to remove that line in the 386 to advert.
    That had to be painfully slow, a 486 crippled to not only a 16 bit bus but also an 8-10 MHz bus.

    The only advantages I can see are being able to go in and out of protected mode without rebooting and running 32 bit code.

    It'd be so slow though that money would be better spent on a new machine.

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