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running 486 on Inboard 386

Cimonvg

Experienced Member
Joined
Apr 4, 2009
Messages
287
Location
scandinavia
Hello
The xt-386 class hobby still ongoing, and today I did get my Inboard 386/pc to run an Intel 486 cpu. ;)
I used a "Transcomputer" converter and a few socket extensions. Did buy two used converters, made for IBM microchannel and for Compaq, and they both seems to work. I did not buy the NIB version , so a lack the floppy disc and the manual's.

-2015_03_31_IMG_06299.jpg
(photo from above - Transcomputer module,socket extension and Inboard )

-2015_03_31_IMG_06297.jpg

The speed is relativ to the clock speed of 16 Mhz - reasonable, and the two modules seems to have the same speed results. Have to test with other CPU's but a quick test with Evergreen 586 did not start at all. Cyrix 486 and Intel 486dx did start like expected.

BUT this cpu modification draws alot of heat - and a do not dare to mount the chassicscover, it is like heavy heat exhaust.

My windows 3 did not start - have to look into it, or try with a new windows installation. DOS, drivers,NC commmander and Checkit did run like expected.

-2015_03_31_IMG_06296.jpg -2015_03_31_IMG_06298.jpg

And yes, did only get it working hours ago, and perhaps some "funny" obstacles lay ahead :confused:.
/cimonvg
 
Hello
The xt-386 class hobby still ongoing, and today I did get my Inboard 386/pc to run an Intel 486 cpu. ;)
I used a "Transcomputer" converter and a few socket extensions. Did buy two used converters, made for IBM microchannel and for Compaq, and they both seems to work. I did not buy the NIB version , so a lack the floppy disc and the manual's.

View attachment 23492
(photo from above - Transcomputer module,socket extension and Inboard )

View attachment 23493

The speed is relativ to the clock speed of 16 Mhz - reasonable, and the two modules seems to have the same speed results. Have to test with other CPU's but a quick test with Evergreen 586 did not start at all. Cyrix 486 and Intel 486dx did start like expected.

BUT this cpu modification draws alot of heat - and a do not dare to mount the chassicscover, it is like heavy heat exhaust.

My windows 3 did not start - have to look into it, or try with a new windows installation. DOS, drivers,NC commmander and Checkit did run like expected.

View attachment 23494 View attachment 23495

And yes, did only get it working hours ago, and perhaps some "funny" obstacles lay ahead :confused:.
/cimonvg

I'd be real interested in how much of a performance gain you achieved with you mod. Also, do plan on trying WIN98 on your convert. WIN95 runs real well on my stock 386.

Tom
 
I have to test this new setup some more. And get back with the results. I think my Evergreen (486 with 132PGA) is a bid faster then these intel486 - perhaps a Cyrix486x2 (168PGA) would be even better ??
Did try windows 95 (with original Intel 80386 in the Inboard) , and it took like hours to install. But at first boot it stopped. Inboard 386/pc needs a new keyboard driver and irq driver , before it will work - I think.
/cimonvg
 
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I have to test this new setup some more. And get back with the results. I think my Evergreen (486 with 132PGA) is a bid faster then these intel486 - perhaps a Cyrix486x2 (168PGA) would be even better ??
Did try windows 95 (with original Intel 80386 in the Inboard) , and it took like hours to install. But at first boot it stopped. Inboard 386/pc needs a new keyboard driver and irq driver , before it will work - I think.
/cimonvg

Great to see somebody else who bought these adapters. I got the compaq version, but I wasn't sure how likely it was to work on my generic 386 motherboards.

Did your compaq dingus come with the thing that plugs into the 385 cache controller socket too?

It seems strange to me that your evergreen adapter would be faster. Isn't that based on a TI chip? Are you sure the 8k cache works on your i486? The Cyrix version of a real 168pin 486 should be 10% slower than the intel part.

You should try fitting this adapter with a VRM and running an AMD5x86 in 4X mode.
 
Hello
The xt-386 class hobby still ongoing, and today I did get my Inboard 386/pc to run an Intel 486 cpu. ;)
I used a "Transcomputer" converter and a few socket extensions. Did buy two used converters, made for IBM microchannel and for Compaq, and they both seems to work. I did not buy the NIB version , so a lack the floppy disc and the manual's.

I bought them :p
When i have the stuff here, i will post the disk-images and manual (if anything like that is in the boxes).
 
hello again
-thank you for the comments-
Today i did few tests. The Evergreen "Rev to 486" runs like a charm, and performs quite well. The CPU runs right away my windows installed with a ordinary 386.
Perhaps i use a wrong version of driver - changing switch from /1 to /2 should give a boost in performance, today it gave the same result (?). Conclusion, the speed test represent properly x1 speed. (Rev to 486 , capable of x3 !).

-2015_04_01_IMG_06302.jpg -2015_04_01_IMG_06303.jpg

(look this 486 in PGA132 runs faster then the Intel 486 PGA168 :nervous: .. I did mount a fan on top of the "Rev to 486")

-2015_04_01_IMG_06304.jpg -2015_04_01_IMG_06305.jpg

Did a test with the Cyrix 486, on the IBM version Transcomputer board.
The Windows 3 installed with 386 and did run with Rev to486 ,did not run... but i did find an old backup of windows 3.1 - and it did start as expected in standard mode. The Cyrix do not develop that much heat, and about 1 hour later the cpu is still only hand temperature.
/cimonvg
 
That's pretty cool. And now a 3,3V adapter on the adapter and run a 486DX4 @ 100 MHz ... Or even the AMD 5x86-133 ...

Unfortunately there is not enough space for such adapters in my Walkstation and M380XP1.
 
That's pretty cool. And now a 3,3V adapter on the adapter and run a 486DX4 @ 100 MHz ... Or even the AMD 5x86-133 ...

Unfortunately there is not enough space for such adapters in my Walkstation and M380XP1.

Could you explain in more detail how one would go about finding and adding a 3.3V adapter on the adapter and run a 486DX4 - not grasping the practical how to of that.

Sounds wonderful, but I've found Win 3.1 runs pretty well in standard mode with the Cyrix 386>486 20/40, and as mentioned, the heat is manageable even without a heat sync. Going to a 50MHz or 100MHz will make Win 3.1 fly in standard mode, but nothing I've tried so far will let Win3.1 run in enhanced mode with out the keyboard getting disabled after sending the first character. Ironically, everything else works perfectly in 3.1.x enhanced mode - Grrrrr. I think it is something to do with the BIOS on the InBoard/PC. I don't know what would happen if we tried Win 95 - the same limitation might or might not remain - would be really interesting to find out.

Regards,
Mike
 
I don't know what I'm talking about, but in the back of my head I'm thinking "protected mode" "A20 line" "XT keyboard controller". Just mentioning it in-case it inspires someone with more knowledge to ponder. I'm wondering if it's related to your keyboard difficulties.
 
Oh I think you are onto it! The A20 gate (bit 1) needs to be disabled (I think) when going into enhanced mode and enabled back when going into standard mode. There are some keyboard commands (DDh and DFh that will do that given the keyboard has the right controller, but it doesn't appear to be something that can be entered from the keyboard, but from software. In interesting thing I found is that SMC made a super I/O controller chip, the FDC37C93x Plug-and-Play Compatible Ultra I/O Controller for AT bus I/O cards that had pins to set to control the A20 bit 1 state. What I don't know is on which I/O card implemented the FDC37C93x controller chip if I am right that the FDC37C93x is a chip and not a board.

Regards,
Mike
 
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Ah, your Rev to 486 is based on IBM Blue Lightning. That would explain why it's faster. It has 16kb internal cache.

Some Rev to 486s use the TI chips, which are slightly modified Cyrix DLCs.

I wonder why the Evergreen 586 didn't work out. Sometimes the L1 cache or CPU ID confuses the BIOS. Maybe an AMD DX4 or Cyrix 5x86 would work better.

Please send me the software and manual for the Transcomputer compaq version when it is made available.
 
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Ah, your Rev to 486 is based on IBM Blue Lightning. That would explain why it's faster. It has 16kb internal cache.

Some Rev to 486s use the TI chips, which are slightly modified Cyrix DLCs.

I wonder why the Evergreen 586 didn't work out. Sometimes the L1 cache or CPU ID confuses the BIOS. Maybe an AMD DX4 or Cyrix 5x86 would work better.

Please send me the software and manual for the Transcomputer compaq version when it is made available.

I have used a Kingston 133mhz upgrade and it works. I get about 93mhz on the CPU with a 46mhz oscillator on the inboard.
Without the right tool you won't get more speed out of any 486 than the 386 compatible 486 from cyrix and TI.
With the cache enable tool i got the 20-fold integer speed that i got on the AMD5x86 at first and the FPU got 5-6 times faster.

Here are the contents of the needed Floppy:
View attachment transcomputer.zip

;-)

-Jonas
 
hello
thank you jonas for the tip and files.
You got the Rev.C model my model is Rev.D. My Evergreen 5x86 (with AMD 5x86) did not Boot/start at all ..?
I just bought a used Rev.C. and have to try again. keep you posted.
/cimonvg
 
I just snagged one of these myself, for $20 its worth the risk. Thanks also for the software Jonas. OK, if I want to go all out with something like a Kingston 133mhz upgrade. Can you share exactly what CPU part number that is are we talking a Kingston TC5x86/133 DE or something like this: http://www.amazon.com/Kingston-Turbochip-133-Processor-486-Based/dp/B00004Z7OD?). I understand have to replace the oscillator with a 46mhz oscillator. I have no idea how to do that or where to get the oscillator or even identify the existing one on my InBoard (OK, I admit it, I am more of a SW guy but willing :)

Regards,
Mike
 
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I just snagged one of these myself, for $20 its worth the risk. Thanks also for the software Jonas. OK, if I want to go all out with something like a Kingston 133mhz upgrade. Can you share exactly what CPU part number that is are we talking a Kingston TC5x86/133 DE or something like this: http://www.amazon.com/Kingston-Turbochip-133-Processor-486-Based/dp/B00004Z7OD?). I understand have to replace the oscillator with a 46mhz oscillator. I have no idea how to do that or where to get the oscillator or even identify the existing one on my InBoard (OK, I admit it, I am more of a SW guy but willing :)

Regards,
Mike

My last Inboard 386 was stable with a 50mhz oscillator. It died after i tried one of my 8mb prototypes. The current Inboard only works up to 46mhz. All inboards are stable with a 40mhz oscillator. You may have to test out several 50mhz oscillators until you find one that works. The PALs on the Inboard will get extremely hot at clock rates of more than 45 Mhz.

The oscillator is the metallic thing with 4 pins and there should be "32 mhz", "32.000" or something like that on it ... look at the right side of the coprocessor. The best method is to unsolder the oscillator and install a socket. This way you can try several different types of oscillators. When you have found you perfect oscillator you can tie a stap around the oscillator to fix it to the socket. You have to be cautious to not damage the Inboard if you try to unsolder the oscillator. The Inboard is a multi layer board and small cuts or little damage can make it nonfunctional. You should ask a professional if you have doubts that you are able to do this yourself (there are some extremely skilled people in this forum). The right oscillator might be hard to find. There are several sweet spots that are dependent on the components. Ech Inboard may have a different behavior when it comes to top speed. I have tried a 45mhz osc. and that did not work. the 46.3xx osc. works but the 2Mb expansion has problems with this. 40mhz is no problem at all. As i have said the other Inboard was going to 50mhz stable with the same 2mb expansion. i have even let it run at 54mhz without the 2mb expansion. The Pals should be actively cooled at more than 40mhz.

I have bought the Kingston TC5x86/133 from the same guy (we made a special deal ;-) ) as well. It works like a charm. The 5x86 may need more than 16Mhz base clock. The oscillator upgrade to at least 20mhz base clock might be needed for them to work. 40mhz osc. = 20mhz base clock = 80mhz internal 5x86 clock.

-Jonas
 
OK, sounds good. I found a new OEM boxed Kingston TC5x86/133 with software for $26 -that seemed like a deal. I'l probably play it safe and go with a 40mhz oscillator since I also have the original 4MB expansion. My hope is that the 386>486 socket adapter doesn't interfere with the 4MB piggyback daughter card and clears it. I see the oscillators come in various shapes and sizes so I'll look for one the same shape/size as the original one on the InBoard. Yah, I might find someone experienced to do the soldering who is less likely to be clumsy like myself. I'm not sure how to find a socket...guess it will also have to match the right size/shape of the original oscillator. One question, after I replace the oscillators with a 40MHz, would the original 386DX CPU and or the Cyrix 386>486 20/40 I have in there now continue to work with the upgraded oscillator if I needed to back off the adapter and the Kingston TC5x86/133, or would have have to also revert back to the original stock oscillator?

Regards,
Mike
 
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My 386DX 16 was capable of 20mhz. It got a bit hot though and i switched to the ti486SXL later on. If you use a socket for the osc you can put the 32 mhz osc back in.
You will need to use a 386 socket between the adapter and the board if you want to use the 486 adapter with the memory expansion.
 
Thanks. One last question. I think what I might do in the order of things is first try using just the 386-486 upgrade adapter with the 386 socket adapter and my current Cyrix 20/40 CPU without changing the oscillator just to very that the adapter works by itself using a known working 486 upgrade chip. Then I'd like to swap out the Cyrix CPU and replace it with the Kingston CPU - again, not replacing the oscillator yet just to make sure everything is functioning properly before changing out the oscillator, then finally, change out the oscillator using a socket and and go from there. I like to work in steps so as not to have to work backwards to find out which component didn't work right in the chain. - does that make sense? When I get to the point of using the Kingston 133 CPU before changing the oscillator, whereabouts shoud I expect the performance to max out, at 33MHz but with the 8M cache enabled?

Regards,
Mike
 
I like to work in steps so as not to have to work backwards to find out which component didn't work right in the chain. - does that make sense?
That makes lots of sense. I figured that out loooong ago when assembling computers. After putting a few together that didn't work as expected (or just didn't work) I figured it was better to fire it (them) up after each stage of assembly and if all was well to move on to the next stage. It just doesn't make sense to build on top of an error of some sort.
 
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