I actually left a few other pots in my shopping cart, since they were cheap enough. One was a 5k, so that'll make it a ilttle easier...

My xi8088 doesn't boot at all with the active terminator installed. No beeps, no video init, nothing.

I verify 2.68v and 5v on the test points.

*edit*

I installed one of the capacitors in the wrong location. C9 is missing.

*edit2*

I moved the cap to C9, still nothing.

keenerb wrote:

My xi8088 doesn't boot at all with the active terminator installed. No beeps, no video init, nothing. […]
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My xi8088 doesn't boot at all with the active terminator installed. No beeps, no video init, nothing.

I verify 2.68v and 5v on the test points.

*edit*

I installed one of the capacitors in the wrong location. C9 is missing.

*edit2*

I moved the cap to C9, still nothing.

You have it adjusted for 2.7 volts? Also, you left RN9 unpopulated? Double check that all resistor networks are installed with the correct polarity?

Scott

I believe so, assuming the polarity markings on the board were correct.

C1, C9 are 1uf caps.

RN1, 3, 5 have polarity pin on right side

RN11, 13 have polarity on left side

RN7 has polarity on right side.

RN9 is unpopulated.

It reads 2.68 volts across VTERM, an 5.06 across 5v.

I haven't tried this with my Malinov backplane; is that what you're using?

Actually it seemed to work in my 4-slot backplane, but not my 10-slot backplane.

The 10-slot has solder pads for resistor packs, presumably to add ISA termination, so possibly that has something to do with it.

Not working in my malinov backplane either.

And now its' not working in my 4-slot backplane either.

I must have done something wrong. I'll look it over.

keenerb wrote:

I haven't tried this with my Malinov backplane; is that what you're using?

Yep, I have the Xi 8088 installed in the second slot from the left, and the terminator board installed in the rightmost slot.

What value resistor did you choose? 220 ohm?

One thing you could try is removing resistor packs and see if one line in particular is causing your board trouble. That's how I realized that RN9 was causing issues. RN13 and RN11 (in that order) are probably ones to be suspicious of.

Scott

Just to see what would happen, I upped my oscillator from 24 Mhz to 30 Mhz. It's been successfully running checkit memory tests for about 24 hours. This is with the bus terminator board installed.

Now, if only I could find a 36 Mhz oscillator...

Scott

Any new developments, keenerb?

Mine has started exhibiting a strange symptom today -- I bought an Avocent SVIP1020 KVM-IP to serve as my console, and the Xi 8088 starts behaving badly when the mouse cable is connected. This morning, about a dozen attempts couldn't get a successful boot out of it. Unplug the mouse cable and it starts to boot fine again. Weird.

Scott

how is your mouse jumpered onthe xi8088 board? using irq12 or isa with J3?

I'm got mouse connected and using a Trendnet TK205 kvm. wonder now if I should pull the mouse 🤣. so many discrepencies

It may not have been what I thought it was... turns out the Xi 8088 wasn't seated well in the backplane. Just fussing with the card was giving intermittent boot failures. I'm not sure if it's something a little tweaked with my case, or if the bracket doesn't line up quite right, but I went ahead and modified the bracket slightly and now it seems to be working fine.

So perhaps nothing to do with the mouse...

I haven't done anything else with the xi8088 and the backplane since my last test.

I was trying it with another SBC isa board, a Viper808, but after tinkering with it for a few days I found a manual online and apparantly it needs ECC ram, which I didn't have!

I'm ordering enough parts to build a second terminator with sockets rather than directly soldering the resistor packs, for easier troubleshooting, but will be a while before they get here...

keenerb wrote:

I'm ordering enough parts to build a second terminator with sockets rather than directly soldering the resistor packs, for easier troubleshooting, but will be a while before they get here...

That's on my short list of things to do also. If nothing else, I'd like to know exactly which ISA bus lines are the ones that are making a difference.

I've given up on my board. sick and tired of it. Ordered an 286 SBC off ebay for cheap 😒

I did too, got distracted with some other stuff, also SBC related. SBCs are my only collection other than my Tandy machines.

I just realized I never actually ordered the parts for the second, socketed board. Still sitting in my Digikey cart, just placed the order.

I'll test out the active terminator well and report back in a week or two.

The last thing I worked on was a speech synthesizer board, which was pretty successful.

I'm still planning on building up a socketed active terminator so I can play with terminating various pins and figure out which lines the termination helps with and which it doesn't. I have all the parts necessary to do this, just haven't had the time. The Xi 8088 has a mind of its own. I swear, if I don't use it for a few weeks, it'll hold a grudge and misbehave for the first half hour after powering it up, terminator board be damned. Maybe the thing needs to warm up.

I do wonder if buying the cheapest China eBay bypass capacitors, IC sockets, and other minor components I could get my hands on wasn't perhaps a mistake. Maybe the variability of these minor components is why we're seeing such a range of different behavior.

Yesterdays reliability issues seem to have been resolved by unplugging the CPU card and plugging it back in.

I wonder if the ISA connectors I used on the backplane are crappy? I seem to have had multiple issues that have been related to card/backplane issues, particularly with the CPU card.

Spent some time playing with the active terminator board over the weekend.

I configured my Xi 8088 using the buffered RAM daughterboards that I mentioned a page or two back. These boards will reliably prevent the Xi 8088 from booting unless the active terminator board is installed, so it was an easy configuration to work with. I built up a second terminator boards with sockets installed, and proceeded to install 220 ohm resistor packs until I found which resistor pack was responsible for transitioning the machine from a non-bootable to bootable state. It was RN5, the resistor pack attached to the data bus. It still seems a little bit wonky and unreliable, but it's interesting that in my case that one resistor pack was sufficient to go from not-bootable to bootable.

Will play with the other resistor packs some, as well as perhaps resistor values and see if I can determine anything more.

Anyone here still working on their Xi 8088 ?

I spent some time building a MIDI card for mine (based on HardMPU, see the thread here at vogons) and developing a midi player. In general, I am capable of accomplishing useful work on the Xi 8088, though it continues to have strangely unpredictable misbehavior. It's frustrating that I can't seem to track down a root cause, or even characterize the misbehavior. It's like 99.9% working, but that 0.1% is a killer.

Not seriously. I couldn't find sockets that worked with the resistor arrays well, so I never went any farther with the active terminator.