Nice find! V30 stuff is rare - at least where I live...
And you are correct, xt-class machines work only with low density drives and judging from your tests this is also the case for your setup... Maybe you'll be able to write a bios rom with HD-FDD support added or use an xt-ide controller ?
These are the kind of inconvenient things that xt ownership comes with 🤣

Nice, I'll be looking forward to seeing a scan of the manual and a copy of the disk. I've had one of these boards for a while, and always wondered if there was anything interesting hidden in the manual.

As far as I can tell the BIOS does not support HD floppies. You're going to have to boot with a 360k or 720 diskette. I suggest XT-IDE as soon as possible.

Did you say this board supports AT keyboards?

^^^^ I tried low density diskettes in high density drives, but it looks likeit knows they're high density drives. I *seem* to remember this issue when working on XT computers and drives in the middle of the 90s (but I was a kid then, literally) but because that was so long ago, I can't clearly recall the workaround, or even if there was one.

I'm tempted to pull apart my Hyperion machine and pull a 360k out of there (hopefully the interface is standard?) but I'm swamped with other projects of the car nature now as it is warming up and can scarcely spend the time on it. Unless I come across a low density drive soon, this will get re-sold as it has theoretically served its purpose.

It does not give me a keyboard error when I plug in an AT 101 key and boot up (even the three LED lights light up as they would in an AT POST on say, my 286 and 386) and it does respond to commands (at least, when I press the button down when it asks for another diskette) but what scan code it sends to the computer and if it maps properly, I can't be certain of until I find a low density drive.

I'll upload the utilities today if I can. I really want to try them out, as it looks like you can change the speed on the fly with a TSR program! 4.7, 7, and 10 MHz options. I wonder what that does to the Turbo LED. The manual will have to wait, but don't hold your breath, it's not terribly exciting (and has a decent amount of Engrish in it) and overall not too badly written.

Is there any way to boot this up otherwise?

Congrats on finding this board. I did look for one for quite a while but these are very rare and hard to find. I mitigated this by now owning a Tandy 1000 SL which i very succesfully overclocked by over 100%. Tandy were conservative with the SL as making it too fast would remove market for the TL.

You can always try and use an ISA NIC for its boot ROM, there are plenty of HD floppy BIOSes out there.

That tandy with the decoupled ISA bus is super cool. I didn't even know that was possible with an XT. I wish they were all like that...and I wish there were faster 8087s too.

Would it be possible to use an 80287 on an 8086 based board, or are they not pin-compatible? IIRC there's some 25 MHz 286s, so there may even be co-pros that high.

I have several ISA NICs, how would/what do I look for? Only one is 3COM with RJ45, the other two are BNC/Vampire tap. Any way to use those, especially the latter, as they're somewhat useless to me.

Attached is the JUKO NEST utility diskette contents. Please upload it to your driver site.

I already looked into the 80187 and the 80287. I don't believe it's possible to interface either to an 8086. The 80187 is actually very similar the 80287XL in many ways, but I don't believe they're pin compatible either.

I also had a crazy idea to interface an 8087 to an 8086 running at half the speed of the CPU, but I don't believe that's possible either. Those chips interface in a very unique way and I don't think it's possible to decouple them.

BTW, I think you're right about IIT FPUs going up to 25MHz. I know for a fact they made a -20. I think there is a -25 as well, but it must be very rare.

I recall seeing a Harris 25MHz up for grabs on a Polish auction site.

indeed, it exists!

http://www.cpu-world.com/CPUs/80286/Harris-CS80C286-25.html

Oh well actually that's for the CPU.

Jed118 wrote:

I recall seeing a Harris 25MHz up for grabs on a Polish auction site. […]
Show full quote

I recall seeing a Harris 25MHz up for grabs on a Polish auction site.

indeed, it exists!

http://www.cpu-world.com/CPUs/80286/Harris-CS80C286-25.html

Oh well actually that's for the CPU.

this is my Harris 25MHZ 😀

ReL wrote:

this is my Harris 25MHZ 😀

what do You do with it? do You have an ems board? show us the innards please?

mrau wrote:

what do You do with it? do You have an ems board? show us the innards please?

Conf:
Motherboard : PC 286 Advanced Computer Technology
Cpu: HARRIS CS80286-25
Memory: 4 Mb SIMM 1Mb x 4
Hdd: Western Digital Caviar 170 Mb 3,5" Ide
Fdd: 1.2 Mb 5.25", 1,44Mb 3,5", Streamer COLORADO Jumbo Tape 60 Mb
Vga: Super Vga UMC UM85C408 kartica 1Mb

I have ems memory, the computer was made when I was born, it was intended for games of course it is stronger than 386sx-25, they can not see the processor because it would be easy to remove the power since it is below it ..

Jed118 wrote:

So I got a JUKO NEST board, practically NIB with an NEC V30 fitted

I have this board that is a bit like yours to the same thing about JUKU only a different model, so here I share with you..

CPU is NEC V20

Where's your RAM? 😁

Jed118 wrote:

Where's your RAM? 😁

256kb for the test is quite enough 😀,The smallest problem is to add more memory

Hmmm without parity (shakes finger) - I guess for a test it's OK. Do you have a manual for it?

Jed118 wrote:

Hmmm without parity (shakes finger) - I guess for a test it's OK. Do you have a manual for it?

This is one of my old motherboards, I have the parity and memory to put in it, I just removed it since I have a lot of boards that use this memory this one can work from now with a 256k boot system which is quite enough

yea i have manual
https://imgur.com/gY1ccBW

Looks like yours supports the Parity Off option too. I've got EGA selection on mine. Curiously, mine supports min 512K of RAM.

Attached is the manual. Someone please upload it to the manuals site.

(Edit - it's a scan of a photocopy, it was hard to keep straight, however it is legible)