smbaker wrote:

Also be sure to check the seating of all cards in the backplane. I'm not entirely sure why, but sometimes I'll have POST errors until I fidget with the Xi 8088 card a few times and then it'll work fine for several days or even weeks. I used some eBay card connectors on my backplane -- maybe they weren't the best quality.

For checking solder bridges, I'm a fan of using a stereo microscope. AmScope has some pretty affordable ones. That big SMD chip on the VGA card in particular took me multiple passes of retouching it, picking at the pins to make sure they were soldered down good, cleaning up bridges, etc.

I've found I had to reseat the cards a few times. I assumed it was because I don't have them properly mounted in a case. I'll have to look in to that further.

I too use an AmScope stereo microscope, I went to the extreme of getting a proper usb 3.0 camera for it. I find it absolutely invaluable for smd work like this.

Hello,

I decided to buy a working VGA card on eBay and check my board with it. Anyway can I do something else without monitor? For example, I have already soldered floppy card ( http://www.malinov.com/Home/sergeys-projects/ … sa-fdc-and-uart but without serial port components) and floppy drive itself. Will it make any attempts to boot from FDD without connected monitor and with defaults BIOS settings)?

I built the Lo-Tech 1MB board today. I haven't done a SMD project in a while, and I sure was rusty... Hilights included soldering the SRAM crooked and having to redo it, soldering 74HCT139 in place of 74HCT138 and having to redo it, and somehow bending a pin on the 74HCT30 leading to a cold solder joint. The first two problems I caught before powering up. The third took some debugging.

Anyhow, I pulled the two SRAM chips from the Xi 8088, plugged the Lo Tech board into the ISA bus, and set SW1 to all on and SW2.1 and SW2.2 to on. The Xi 8088 booted with 640 KB and passed 10 passes of checkit. This worked both with and without my bus terminator board installed.

Just another data point...

ETA: Ran check-it all night with no problems, but the system failed about 2 hours into the "Champions of Krynn" test this morning.

Scott

Is Lo-Tech still making boards? They had a Tandy audio expansion board which would be fantastic for early PCs.

gdjacobs wrote:

Is Lo-Tech still making boards? They had a Tandy audio expansion board which would be fantastic for early PCs.

Lo-tech licensed the design to texelec.com and you can buy them there now. Both bare PCBs and completed boards. I don't see the Tandy board listed on the site though.

Scott

hmm thats interesting.

smbaker wrote:

I built the Lo-Tech 1MB board today. I haven't done a SMD project in a while, and I sure was rusty... Hilights included solderin […]
Show full quote

I built the Lo-Tech 1MB board today. I haven't done a SMD project in a while, and I sure was rusty... Hilights included soldering the SRAM crooked and having to redo it, soldering 74HCT139 in place of 74HCT138 and having to redo it, and somehow bending a pin on the 74HCT30 leading to a cold solder joint. The first two problems I caught before powering up. The third took some debugging.

Anyhow, I pulled the two SRAM chips from the Xi 8088, plugged the Lo Tech board into the ISA bus, and set SW1 to all on and SW2.1 and SW2.2 to on. The Xi 8088 booted with 640 KB and passed 10 passes of checkit. This worked both with and without my bus terminator board installed.

Just another data point...

Scott

Awesome,
Can this be used to extend the memory of the XI8088 using it as ems or xms?

Sir Isaac wrote:

Awesome,
Can this be used to extend the memory of the XI8088 using it as ems or xms?

The 1MB board is strictly for the 0-1MB range, so it's completely redundant with the Xi 8088's onboard SRAM. This is indended for systems like the IBM 5150 that might have very little onboard RAM, as little as 16 or 64 KB.

However, what Lo-Tech does have is a 2MB EMS board, which is to be the next thing I'm going to build. Slightly more involved, with 4 RAM chips and around a dozen other chips. All surface mount. I'm hoping to get mine completed this weekend, the 1MB board was my "practice run" to make mistakes on.

Scott

smbaker wrote:

The 1MB board is strictly for the 0-1MB range, so it's completely redundant with the Xi 8088's onboard SRAM. This is indended fo […]
Show full quote

Sir Isaac wrote:

Awesome,
Can this be used to extend the memory of the XI8088 using it as ems or xms?

The 1MB board is strictly for the 0-1MB range, so it's completely redundant with the Xi 8088's onboard SRAM. This is indended for systems like the IBM 5150 that might have very little onboard RAM, as little as 16 or 64 KB.

However, what Lo-Tech does have is a 2MB EMS board, which is to be the next thing I'm going to build. Slightly more involved, with 4 RAM chips and around a dozen other chips. All surface mount. I'm hoping to get mine completed this weekend, the 1MB board was my "practice run" to make mistakes on.

Scott

I have the 2MB lo-tech board in the mail. (PCB only) Hopefully in a few weeks after my next parts order, I'll be able to build it. It will be interesting to play with on the XI8088.

I built the 2MB EMS board today. It's working fine in my Xi 8088... at least so far.

One thing that's annoying about these Lo-Tech boards is that they seem to be a nonstandard size -- the standard keystone bracket won't fix it, so I have no ISA bracket attached to it. Seems like it would have been insignificant cost to just make the thing a tiny bit longer. I'll have to see if I can custom fab some kind of bracket to go with it.

Scott

Ran an all-night checkit on the EMS board. It failed at passes 123 and 124, and then checkit halted the memory test due to too many errors.Will continue to let it run during the day today to collect more data.

Scott

smbaker wrote:

I built the 2MB EMS board today. It's working fine in my Xi 8088... at least so far.

One thing that's annoying about these Lo-Tech boards is that they seem to be a nonstandard size -- the standard keystone bracket won't fix it, so I have no ISA bracket attached to it. Seems like it would have been insignificant cost to just make the thing a tiny bit longer. I'll have to see if I can custom fab some kind of bracket to go with it.

Scott

On the lo-tech wiki page I found all the brackets they use. https://www.lo-tech.co.uk/wiki/Lo-tech_ISA_Sl … Brackets#Type_3
I can't see them making their own brackets but you never know. Since there is no part numbers for them it makes it a bit harder to track down. They do give all the dimensions though.

smbaker wrote:

Ran an all-night checkit on the EMS board. It failed at passes 123 and 124, and then checkit halted the memory test due to too many errors.Will continue to let it run during the day today to collect more data.

Scott

Interesting it ran so long then halted. Wonder if there is a weak solder joint that's failing after it's warmed up?

Or just hot chips in general returning wrong values when they get too hot.

Heat is a huge contributor to crashes and hangups.

Sir Isaac wrote:

Interesting it ran so long then halted. Wonder if there is a weak solder joint that's failing after it's warmed up?

Even more interesting that it happened again today, on passes 123 and 124. I'm thinking there is a software bug involved, either in the EMS driver or in checkit itself. Hardware failure shouldn't be exactly reproducible. There should be some randomness involved. I'm going to run the test again.

Sir Isaac wrote:

I can't see them making their own brackets but you never know.

I did some googling yesterday and there are blog posts where they 3D printed their own brackets. I just can't see any reason to do this, when making the board a quarter inch longer would permit the use of a $2 standard bracket.

Scott

I wonder if you could make an L shaped standoff from off the shelf material, then cut and drill it to the right length for your card. Printing a bracket seems excessive.

smbaker wrote:

Even more interesting that it happened again today, on passes 123 and 124. I'm thinking there is a software bug involved, either in the EMS driver or in checkit itself. Hardware failure shouldn't be exactly reproducible. There should be some randomness involved. I'm going to run the test again.

Now that's odd. Is there any way to test the patterns in those tests using a simple script in dos? Maybe using qbasic or something?

smbaker wrote:

I did some googling yesterday and there are blog posts where they 3D printed their own brackets. I just can't see any reason to do this, when making the board a quarter inch longer would permit the use of a $2 standard bracket.

Ya it seems like alot of work to me. It would be like making your own potentiometer rather than building your circuit around parts that are available. 🤣
Maybe they screwed up the initial board design and just went with it. 🤣

gdjacobs wrote:

I wonder if you could make an L shaped standoff from off the shelf material, then cut and drill it to the right length for your card. Printing a bracket seems excessive.

If need be, this is probably what I will do. 3D printing it is excessive IMO too.

gdjacobs wrote:

I wonder if you could make an L shaped standoff from off the shelf material, then cut and drill it to the right length for your card. Printing a bracket seems excessive.

I have some of these 4-40 L-brackets from Sparkfun: https://www.sparkfun.com/products/10228. My plan (unless I come up with something easier) is to use those together with a small spacer.

smbaker wrote:

making the board a quarter inch longer would permit the use of a $2 standard bracket.

except PCB cost$ is by dimension. adding another 1/4" by whatever height * number of boards would be a huge expense.