What does the silk screen in the middle of the socket mean?
Posted by king_john651@reddit | vintagecomputing | View on Reddit | 55 comments
Just been cleaning and debattery-ing this new to me board and saw that this has provisions for a 386. Does this mean it treats a 386 as a co-processor or is this a weird one or other thing?
thespirit3@reddit
Given the jumper settings, it looks like the board can take either a 486 or a 386. Interesting!
StuE2@reddit
Being old, as I am, I can confirm this was a board that could take either 386 or 486. I expect you could install both and use the jumper to switch, but why would you? I don't know if it would try and power both at once and it has been 35ish years since I saw one. The purpose was to allow you to have a 386 for now and upgrade your chip later. Remember that upto a 486SX33 (or maybe the D?) you didn't need a heatsink.
Theres no benefit to using the 386, as there isn't even anything that it can do that the 486 won't.
BobChica@reddit
The 386, specifically AMD's am386, did have one important advantage over early Intel i80486 processors: clock speed. The first variants of the i486 were released at 16 and 20 MHz while AMD had pushed the 80386 to 40 MHz. With VESA local bus video cards and disk controllers, this could provide a pretty substantial performance boost.
Scoobysnax1976@reddit
The 486 did the same thing when the pentium came out. I remember ads for 486dx4s running at 100Mhz when the pentiums were running at 75.
BobChica@reddit
The first Pentiums (P5) were only offered at 60 and 66 MHz. The 75 MHz (P54C) part was released alongside 90 and 100 MHz versions. The original P5 was also a 5 volt chip and ran very hot. Additionally, the P5 was the one with the infamous FDIV bug.
AMD had versions of the 486 running at 120 and 133 MHz. I had a Am486DX-4/120 with a Tseng Labs ET4000 VLB graphics card that was a phenomenal gaming rig for its day. Managing a computer store had its perks.
2748seiceps@reddit
It would require a bit more research to see if you can actually have both. The FLT# pin would have to be one of the jumpers and I'm guessing that they didn't include that because 1) like you pointed out who would want both and 2) they would not only have to include the FLT jumper but make sure the CPU supply is robust enough to handle two processors running at once. FLT doesn't disable the processor just makes it exert hi-Z on all the IO so it still, technically, runs.
FinalJenemba@reddit
The only practical use case I could see for this these days is for original Wing Commander diehards. Sometimes a 486 is a little too fast and a throttled 486 is a little too slow lol.
geko29@reddit
I was able to get the original Wing Commander (or maybe it was WC2) running very well on even an overclocked Pentium Pro.
The trick, as I recall, was to replace WC.EXE from the original game, with the launcher from Secret Missions 2. It was totally compatible with the assets from the original game, and had a function where you could artificially slow the game's processing rate to match your system.
2raysdiver@reddit
This exactly. Wing Commander seemed tied to the 386's clock. I could never get it to run right on a 486.
LousyMeatStew@reddit
I had a couple of friends back in middle school - one had a 33Mhz 386DX while the other had a 25Mhz 486DX - and both complained that Wing Commander 2 ran too fast.
I offered to let them play on my family's computer but as it was a 10Mhz 286, they declined!
StuE2@reddit
Oh OK. It's been a quite a while since I've thought about Wing Commander!
TheMage18@reddit
This is the answer. When the 486 was announced and released, it was very expensive. So some third party board makes kept using the 386 designs but would offer the ability to upgrade to a 486 later. OP's board is one such where you could install/use a 386 (and 387 Mathco), then remove and upgrade to a 486 later.
I would not, however, install a 386/387 mathco while the 486 socket is populated. The VRMs may not be able to handle powering both and some of the I/O lines are likely routed to both. Older boards with jumpers like this only used the jumpers to route which socket had the clock/reset lines connected, leaving the rest just wired as is. When in doubt, read the manual (if you can find it) to confirm if you can populate both types of sockets.
king_john651@reddit (OP)
Yeah I was thinking it was the latter, but hoping for the former. Just checked my collection of CPUs and I do have a 386 I could try with
jaybird_772@reddit
It's definitely an either-or. I don't know if it would be safe to put both in the board.
LousyMeatStew@reddit
You can have both. The jumper determines which socket's reset line is held low. The 487SX operated this way - it used a socket with an extra pin that it could use to hold main CPU's reset line low, which it needed to do since the 487SX was basically a slightly-modified 486DX.
phire@reddit
I wound't be surprised if you could install both and switch by just changing the jumpers while the computer was off. You could wire up a multi-pole switch to easily switch all the jumpers at once.
But there is no way of knowing if such a setup was safe. Do not try it unless you can reverse engineer and understand enough of the motherboard to know it's safe.
jaybird_772@reddit
You might be able to, that'd be pretty cool. But I wouldn't trust that something that needs to be tri-stated isn't and you'd cook one chip, the other, both, or the board. Not worth it without a lot of board info to be sure.
starcrescent@reddit
Interesting, what is the brand model and year of this board?
WingedGundark@reddit
Hybrid 386 and 486 boards aren’t uncommon. They were sold around 92-93 for the budget market. Many had soldered AMD 386-40 CPUs and you had a free socket for 486 if you wanted to upgrade later. Some were like this, which had a sockets for both.
These boards use your typical 486 chipsets and most have VLB slots. Using 486 chipsets with 386 CPUs is relatively straightforward as both are 32-bit platforms and you don’t need to make drastic changes to MB layout or logic to make both CPUs work.
meltman@reddit
My old compaq started as a 386dx but had a 486 socket - which I eventually used.
Consistent_Bee3478@reddit
Just read the text above the socket. It tells you which jumpers to set for either 386 or 486. So definetely not both at on d
deelowe@reddit
Correct. I used to have this exact board. Very popular at the time.
Hoovomoondoe@reddit
I suppose the smaller empty slot is where you would put your co-processor.
Baselet@reddit
It has a text 80387 because it takes a 387 math co-processor.
Booty_Bumping@reddit
So does it explode if it's set wrong?
wysiwywg@reddit
Only one way to find out
zorinlynx@reddit
Back at this time the industry was moving FAST. A brand new PC would start feeling slow only a few years later. So manufacturers found ways to provide more value through upgradeability.
This was one example; buy a 386 now and pop in a 486 later. There were also systems with a slower 486 soldered to the board (an SX/25 for example) and an "OverDrive" socket where you could put a much faster 486 later on, like a DX2/66.
These systems were popular for people who had been burned buying, say, an 8088-based PC and finding it quickly obsolete, upgrading to a 286, it being obsolete only a couple years later, etc...
Things were moving so fast in the late 80s and early 90s. It's not like today where a five year old PC is still fast enough for most things.
NevynPA@reddit
This. Can't say it any better, so I won't! 😎👍
anonThinker774@reddit
There is no way you could use a 486 and a 386 processors on a normal board simultaneously. The chip on the left is definitely the 486DX processor. AFAIK, at least for some early version of 486, shipped without a co-processor, you could add a dedicated co-processor in the empty socket, that is 80386. Might be wrong, I dont have the time to check wikipedia or anything.
Kopfschmerzen@reddit
Not a DX2? Weak sauce.
ReceptionFriendly663@reddit
There is a 386 socket and a 386 math coprocessor socket as well.
BobChica@reddit
The math coprocessor is the i80387.
magnificentfoxes@reddit
Socket on the right is for that.
QuantumParaflux@reddit
I think you have a very rare motherboard. I hope you can clean it up and get it working. Please don't give up on it and replace the caps. And please send us pictures when you have it working and built!
king_john651@reddit (OP)
It works fine, probably needs a bit of work to get the replacement battery backup working judging by how oxidized the traces are in that area. Not too much damage otherwise. I'm against unnecessary recapping because if it works it works, but this one doesn't have electrolytics installed so no worries there
VastFaithlessness809@reddit
This is for an 80386 coprocessor
Denisoiu1242@reddit
This is cool af
Sushi-And-The-Beast@reddit
I have a few of these boards.
No different than the boards with the slut and socket processors.
prefim@reddit
386 CPU (if not using a 486 in the already full socket). there's also an FPU socket for 387. When boards could take more than one type of CPU!
D4t4M0nk@reddit
I used these for my clients. Start them with a strong 386 and upgrade them a year or two later to a strong 486. Or start them with a weaker 486 (very low price) and then upgrade to a better 486. Passed the weaker 486 to one of their coworkers that was on a board like this but still 386. We were all sales people working independently and PCs had just started to get used in our specific industry.
Take advantage of price changes.
spektro123@reddit
AFAIK there were some boards that could take 486 or 386DX (32bit bus) like this one. Earlier there were boards for 286 and 386SX (16bit bus). Those processors are not that different, at least electrically, from each other. They were meant for people who wanted to upgrade later and were made in the transitional periods.
phire@reddit
Looks like you can also use J22 to take a 487 and trick it into working without a 486SX installed.
You can also jumper it for a 486SX (labeled as P23)
Deksor@reddit
You can also do the opposite and trick a 487SX socket into accepting a 486DX CPU (the 487SX isn't a coprocessor for the 486SX, it is an entire 486DX with an extra pin to disable the installed 486SX. Not useful if the 48SX is socketed, very useful if the 486SX is soldered.
Competitive-Unit6666@reddit
Looks like a 486 which had some faster memory cache architecture ... also I think these could be overclocked ( with cooling gizmos) for even greater performance
sparrow_42@reddit
Pretty neat, I honestly don't think I've ever seen a motherboard like that.
gwreijman@reddit
You can remove the 486 CPU and use it with a 386DX CPU. The smaller socket is for a 387 coprocessor.
The 486DX already have a coprocessor in it.
ADDicT10N@reddit
This is the answer. I forgot cool stuff like this existed
Js987@reddit
Boards like this existed during transition periods where one processor was gradually replacing another on the market. You can’t use both, it’s an either/or, but it lets you pick a 386 or 486. The idea being the buyer could get the motherboard and a 386, and then when 486 prices dropped or had the money now remove the 386 and pop in a 486 without paying for a whole new motherboard.
Electronic-Wash8737@reddit
Some similar boards put the 387 socket inside the 486 socket: https://redhill.net.au/b/b-94.php (bottom entry; can't link directly to it, as the anchor name is mistakenly copy-pasted from another board).
PigHillJimster@reddit
The socket was for a co-processor. You could purchase this separately and fit it.
stevevdvkpe@reddit
I had a computer with a motherboard like that. It could take either a 386 or a 486, but not both at the same time. With a 386 installed it could also use the secondary socket for a 387 floating-point coprocessor. You had to move about a dozen jumpers to configure it for one or the other (at one point I upgraded mine from an AMD 386DX40 to an Intel 486DX2/66).
S_Rodney@reddit
Nah, this means the board is an "upgradable platform"... you could go from a 386 to a 486 without changing anything else than the CPUs.
The smaller socket (80387) is for an FPU unit (aka Math Co-Processor) that is separate from the 386.
Since you already have a 486, these sockets are to be left as-is: empty
rpocc@reddit
Of course you can use either 486 or 386, not along.
I have a “two-CPU” 486 board which actually just provides an upgrade option “for dummies” by inserting a superior CPU next to installed SX-25 and change couple of jumpers.
Yours
Lectraplayer@reddit
Looks like you can put a 386 there and move some jumpers, but you really wouldn't need it since you have a 486 in frame that looks like it's part of the board. I'm betting this board was released around the time the 486 first come out, and a lot of people would often get it with a 386 populated, and upgrade to the newest hotness later. It probably would also disable the 386 if you had it there when you put the 486 in and set it up, assuming you didn't have to take it out for one reason or another. It should say in the manual if you can track it down.
themaritimegirl@reddit
My guess is the board was designed to take either an 80386 or 80486 CPU, so whatever CPU you want to use for it, you put it in the appropriate socket and leave the other socket unpopulated.