So in case anybody comes along later and sees my prior cry for help, I am happy to say my problem is solved. My conjecture that the 82c59 PICs were bad was false, as the ISA bus sourced interrupts issue was a red herring. After reading the 82c59 documentation, I learned that these chips have internal pull up resistors on the IRx lines. Hence, the ISA bus interrupts being held HI. Turns out my 80c88 chip wasn't working. I replaced it with a NEC V20 and I get a normal boot. Yay!

I'm not really sure how to determine whether I had a bad 80c88, or the wrong 80c88. The exact model I had was the Intel P80C88A-2. If anybody has some insights on this question, I'd love to learn.

Michael

I just finished building one of these. Getting nothing at boot. No beeps from either the internal speaker or external, nor any video. nothing. I am reasonably sure my backplane is not the problem.

The only signs of life I get are the keyboard lights flashing on power on. The power LEDs work at both ends. Turbo leds work at both ends, and switching it on and off does cause the lights to switch on and off. The CPU does get a slightly warm.

Two things stick out that I am investigating.
I do not know for 100% if my 8284C is CMOS, and I installed the capacitors for the CMOS, and I don't feel like undoing them. I have another one, a Harris 82c84 from ebay coming
I fully admit I did not really understand the instruction for Xiflash, and ended up flashing the 128K BIOS V2 (without XTIDE) using Uniflash on another motherboard, so I do not truly know if I have a good, working BIOS. That said, I have stuck that BIOS into two other motherboards, they both will give a beep that cycles on and off, and I am certain the instruction for that is coming from the BIOS, as they do nothing with empty sockets.

Anyone have any suggestions in the meantime, before I dig through this 28 page thread?

EDIT: I have discovered the 8284C is getting hot, and I get no reading off of pin 12 with my counter.

I have no help to offer with your problem, but was thinking to solder oneof these things myself. Does it have testpoints on the PCB? Are you sure all voltages are correct at those?

I havealready acquired the chipset and the V20 plus a 8087. Does anyone have a spare backplane and mainboard PCB? The est of the stuff I can order myself. But ordering 10 PCBs would be overkill...

^ you can order PCBs from Todd here: https://www.retrobrewcomputers.org/doku.php?i … =boardinventory
last month I got my "ISA Backplane PCB" and "ISA Floppy Disk and Serial Controller PCB" from him, boards were great and arrived fine, Todd is a trustworthy guy

'beeps' come from the bios, have you done visual inspection to see if something is shorted anywhere? everything in correct direction/orientation?

the bios is a simple thing, do you have a rom burner?

I wrote the 128K image in another motherboard.

Right now I have set it to the side until the replacement 82c84 is here, and I made sure it was a proper CMOS version.

So I had two of those flash rom chips, because I accidentally ordered two. I decided, since I had nothing else to lose, decided to get a fresh copy of the BIOS and a feshj copy of uniflash. I hotflashed the chip, using the 128K image, just like last time, and the Xi8088 actually posted this time.

The PC speaker will not beep. It will lock up after a few seconds if the 8087 is installed. I removed it, and checkit says channel 0 on the DMA controller is bad. I am currently doing a memory test.

Hi again Vogons. I have long since gotten this going, but now I hit a new snag. I cannot get this thing to post with anything other than my VGA cards. For EGA, I have an American Microland HEGA480, and an Emulex Persyst EG-8. The XI8088 turns on and does its chime, but nothing appears on screen when using the HEGA480, and garbled text appears when using the Persyst. I know these cards will work with an IBM XT, and have tested them. Has anyone else had problems getting non-VGA cards to work with the XI-8088?

EDIT: Apparently, it won't work at 10.66Mhz turbo speed, but it will work at 9.55Mhz.

EDIT: Sometimes it works. It's really flaky, and I suspect it has something to do with the video memory, which is only rated for 8 Mhz (120ns).

Greetings,

I registered so I could join in on this topic since I am about to dive into the Xi 8088 build with Micro-ATX Backplane.

PCB's included:

• Xi 8088 PCB
• Micro ATX backplane
• ISA SVGA v1.1
• XT-CF-Lite
• ISA OPL2
• ISA Floppy Disk and Serial Controller
• Micro 8088 PCB

Most of my inventory has arrived and will be starting with the backplane this weekend and documenting as I progress with the build.
I have read through all of this thread and kept up with Scott Baker's build when he was doing this last year. Lots of very good input. I've sourced
most of my parts from Mouser, and what I could from US sources.

I hope to contribute to the community with my experience.

There are some boards I'm going to attempt to use before I get all the add-on PCB's built:

• WD1002A-WX1 for an ST506 MFM drive
• Aztech Sound Galaxy BXII sound card
• IBM 1501987 XM Parallel interface
• Trident TVGA8900D (which I've researched to work with 8-bit and found the configuration document)

I'm planning to get the XT-IDE v4 when possible along with the HardMPU from ab0tj

Interesting, I can't believe I didn't know about the MTM Scientific kit.. and the guy who sells them lives very close to me. hah, small world. Maybe I'll order one this Christmas.

My parts, I mostly got from Mouser. I will start assembly of the Micro ATX backplane soon. I have my parts placed on the board and ready to solder. Let the bees rip my flesh off.

Any of you use an SST39SF010A and always get a 76 code when programming with a TL866II plus and the bios128k-2.0 binary?

Berzerkula wrote:

Any of you use an SST39SF010A and always get a 76 code when programming with a TL866II plus and the bios128k-2.0 binary?

Installed the variable picofarad capacitor and now I get a bit more info. 00 is displayed while the decimal dots are fluctuating. Continuing the debugging. I get a code 30 for a few seconds before 00 and no vga output, yet. I’m going to test with another VGA card. There may be something wrong with the TVGA8900D I have. I’ve double checked all the jumpers for 8 bit.

I may measure the OSC pin 12 and read the clock like bloodycactus did when trimming to get the exact frequency. Maybe my VGA card is picky about the clock.

New info found. The TVGA9000 series needs a mod to cut ALE from the bus and solder a jumper wire to that signal to 5V on the video card. I found this info at both Sergey’s site and at Darren’s retro computer site.

http://www.malinov.com/Home/sergeys-projects/isa-supervga
http://darrensretro.blogspot.com/2018/04/for- … as-run-his.html

Wahooo! Received a different VGA card. This one is an XP6676P with a WD90C11A-LR. I've ordered some 256KBx4 70ns DRAM for upgrading to 512KB. The TVGA8900D VGA output was dead. I may troubleshoot that later and have a few different VGA cards on the way to test with this unit.

I don't have precision equipment to measure the OSC at pin 12 of U1, and my primitive oscilloscope with DSVIEW shows it at 14.32MHz. Can't see anymore significant digits. It's probably okay. I've attached some pictures of the video output, backplane, Xi8088 board and the XP6676P with 256KB cache.

My next adventure is the floppy controller and solder some more ISA edge connectors to the backplane. I should have that done very soon.

Looks like I have some building to do.. Nano 8088, XT-IDE, Super VGA, and Adlib.

Have the Floppy/Serial controller built. No need for the ROM at the moment.

I have MS-DOS 6.22 booting from some brand new disks and created a startup disk with some good ole Dysan media.

If anyone looks closely they'll see a mistake. Easily fixed with some tender care.

Hello Wiretap. Glad to see someone else building the Xi8088. I hope your build goes as well as mine. It has been much smoother than most. Creating an ms-dos boot disk brought back memories. I forgot about that. Next up is the WD MFM controller for my 20MB drives.

Berzerkula wrote:

Hello Wiretap. Glad to see someone else building the Xi8088. I hope your build goes as well as mine. It has been much smoother than most. Creating an ms-dos boot disk brought back memories. I forgot about that. Next up is the WD MFM controller for my 20MB drives.

I'm doing the Nano 8088, it was modified from the Sergey Kiselev Micro 8088, but of course is similar in nature. Hopefully it goes well. 😎
Link here: https://github.com/monotech/Nano-8088

Oh, didn't know the Nano yet. I think I will do that as well. Nice, it has the CF onboard.

Greetings everyone!

After a bit of remembering how the MFM cables worked and the WD1002A-WX1, I also realized, someone had put a WX2 bios in the WX1 controller. So I erased it with the UV lamp and burned the Bios Super Formatter v 2.4 F300 and setup the Miniscribe 3425 drives and all went well. With these twisted MFM cables, the middle connector ends up being drive 0 and the end connector drive 1, so that tripped me up for a bit, but I got it sorted. I'm sharing some screenshots. Some with turbo on, too. I have an 8087-1 with the Xi8088 now.

I did low level format the first drive with an interleave of 6 without turbo. I've formatted the others with 5 and with turbo enabled. I've noticed a significant increase in performance with turbo and the interleave of 5. Not sure if I can go to 4 or 3 with this.