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Lo-tech 2MB EMS Board and Tandy TL/2

M

mojorific

Experienced Member
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Nov 1, 2013
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Ontario, Canada
Well, I finally got all the parts needed to make a couple of the 2MB EMS boards that James so excellently designed and built. (http://www.lo-tech.co.uk/wiki/2MB-EMS-Board)

Overall, the soldering of components was relatively easy, and as my first at surface mount soldering it took me a few hours to complete one board. A proper soldering setup with a heat gun and liquid solder paste syringe is crucial, as otherwise it would be nearly impossible with the small components. Getting the correct fan speed and nozzle head was critical as well, as otherwise components would literally blow off the board while I was trying to apply heat.

Tested with a Tandy TL/2, and was unable to use the default E000h address (not recognized). Checked all components again to ensure I placed every chip correctly, and then switched to C000h. It was detected by the LTEMM.EXE software properly after that. Memory testing passed.

However, it is only allowing me to use 1.5MB of the boards 2MB. This could be due to the fact that the Tandy TL/2 is expandable to 768k onboard, and there may be some conflict there. Not exactly sure, but i'm not complaining at this point. 1.5MB is plenty of extra ram for this 286 system.

I plan on building a second tonight, and will update on whether the second one behaves in the same way.

Thanks James!!!
 
E000h conflicts with the ROM paging space in applicable Tandy 1000 systems (TL/SL and later), and the C000h range might conflict with installed expansion boards. A better base address is D000h, which is what I'm using with an Acculogic, "RAMpAT! Plus" in my TL/2. You might try that, and see if it doesn't resolve the 1.5MB issue.
 
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Thanks Cloudschatze. I'll try that.

I have maxed out the cards on my TL/2 with this ram card. I also have a Voyetra V4xxxx Midi Card, Mediavision Thunderboard, and an XT-IDE card. I'll give the D000h address a try tonight to see if it resolves the issue.
 
Actually, based on another post of yours, it looks like you have the XT-IDE at D800h, so putting the EMS page frame at D000h is going to cause problems. Can the XT-IDE be set to CC00h? MSD or QEMM's, "Manifest" can help determine what the current system memory map usage looks like.

How is the Thunder Board working out for you? Its DMA usage renders the PSSJ DAC unusable, but I'm guessing that's not really a concern (or that you have the TB DAC disabled)?
 
This is great to hear!

Re the page frame; the board needs a full 64KB segment, so there can't be anything else present in C, D, or E segments depending on how it's configured. In the Tandy apparently E is out, so leaving C or D. As noted, any option ROMs must be elsewhere. The physical segment is used for each of the four 16KB windows at x000h, x400h, x800h, and xC00h.

Re the RAM size; each of the SRAMs on the board provides 512KB. Partial configurations are supported, that is that only one SRAM could be populated for 512KB EMS.

The initialisation code checks the board via the first window (x000h), so that at least wouldn't be affected by conflicts elsewhere in the segment. That 512KB is missing suggests some physical issue with IC15 (dry joint, solder bridge etc) or possibly IC11 or IC6.

Hope that helps!
 
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I'll reseat the IC15, IC11, and IC6 tonight. I'll also finish building my second board to see if there is a difference. Thanks James! Great work!
 
Alright - built the second 2MB card, and it aswell only sees 96 pages (1.5MB). I checked all my solder joints and everything looks clear. Highly unlikely that I incorrectly soldered two boards with the exact same issue. I ensured all chips were properly seated with the correct pin 1 positions.

This may be an incompatibility with the Tandy TL/2. Please let me know if you would like me to try anything else James. Thank you!
 
It's very odd. I'm updating my hardware test utility to give us a clear view of what is going on, and will report back. The IO Port address is free I presume, though actually a conflict shouldn't matter since the driver only ever writes to the ports.
 
Please try this test utility. Run it like so,

EMSTEST 260 C000

Assuming those are the settings, it will report accessible pages by chip, then do a couple of page mapping tests as well. Please post back the output!
 
Alright - I fixed the cards myself - both cards had different issues. One had a contact problem with IC14, and the other with IC15. Thanks James.

Sorry to bother you with this. Tested Successfully with a Tandy TL/2 on C000 260.
 
Thanks for posting back - and good to see it working! I caught a few bugs in the test code thanks for the output - and hopefully this utility will be useful to others as well.
 
I will be trying the EMSTEST.EXE app tomorrow as I try and figure out the settings for a "Compaq Portable 286 1070 10" with a Lo-tech 2MB EMS and an existing XT-IDE card.
 
Well, I didn't run it yet after all. I spent my time on another Compaq, my SLT. I thought it had a bad floppy drive and I had mentioned in another post. Some one who loves the SLT responded saying he hasn't found any bad floppies in his SLT experiences. So I started cleaning and testing the SLT's floppy and I found an original IBM DOS 3.3 3.5 floppy and sure enough it booted up. When then I ran the SETUP for the Compaq BIOS and it saw it's hard disk. I didn't replace the CMOS battery yet but I knew I could do a soft reboot and the CMOS would stick so doing that, I was let into C: where I probed around and cleaned up some old file from a previous owner.
But your EMSTEST.EXE application day is coming :)
 
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