Tandy 1000EX memory expansion

[Hatta]

I have a tandy 1000EX memory expansion board (25-1062) that is causing memory errors. I've swapped the drams and I get the same behavior. I've even taken the RAM out and it still fails. The tandy works just fine without the card inserted. This card has worked in the past, but I've had it out of the machine for a while.

I'm guessing static fried something? If it's not the drams, what is it likely to be?

When I boot it up, I see something like this:

Memory Size = 384K

Written Read Base Offset
85A4 A5A4 2000 FFFE
...
0A5A 5A5A 5000 0000

 

[Agent Orange]

I have a tandy 1000EX memory expansion board (25-1062) that is causing memory errors. I've swapped the drams and I get the same behavior. I've even taken the RAM out and it still fails. The tandy works just fine without the card inserted. This card has worked in the past, but I've had it out of the machine for a while.

I'm guessing static fried something? If it's not the drams, what is it likely to be?

When I boot it up, I see something like this:

Memory Size = 384K

Written Read Base Offset
85A4 A5A4 2000 FFFE
...
0A5A 5A5A 5000 0000

You might try swapping the chips one by one (keep count of their location) and see if the address of the error(s) change. If so, you probably have a bad chip (or two).

 

[Hatta]

I've already replaced all the drams on the memory expansion and it still gives me errors. Should I open up the tandy and swap the drams on the motherboard? Are they socketed? If the ram on the motherboard is bad, why would it boot normally without the memory expansion inserted?

This is very strange.

 

[geoffm3]

You said it doesn't give you this error if you run without the memory expander card installed? Also, how much RAM do you have installed? You have to set some jumpers for different memory configs on the card.

I'm a bit foggy on this, but ISTR there was a BIOS setup option that you could use to set the EX/HX to skip a memory test at startup. I wonder if you can turn that off with your card removed and get it running enough to run a RAM test program. It looks like there's a utility available on oldskool for testing the expansion card.

 

[Hatta]

Ah jeeze, I bet it's the jumper. I had looked in extech.pdf but didn't see the jumper mentioned. Looking closer at oldskool.org, I see notejump.pdf. I don't have the card right now, but I think the jumper was in position 2 which would enable the 8 empty ram sockets on the card.

Although, it looks from the RAM errors that the problem starts in the first 256k of RAM. Am I understanding correctly that RAM is addressed by bytes, so 2FFFF would be just shy of 192K? Is that where the expansion card puts its RAM? Am I just misunderstanding the notation?

I'll try the jumper either way, just curious about that.

 

[geoffm3]

Ah jeeze, I bet it's the jumper. I had looked in extech.pdf but didn't see the jumper mentioned. Looking closer at oldskool.org, I see notejump.pdf. I don't have the card right now, but I think the jumper was in position 2 which would enable the 8 empty ram sockets on the card.

Although, it looks from the RAM errors that the problem starts in the first 256k of RAM. Am I understanding correctly that RAM is addressed by bytes, so 2FFFF would be just shy of 192K? Is that where the expansion card puts its RAM? Am I just misunderstanding the notation?

I'll try the jumper either way, just curious about that.

I believe you're correct, that should be the very end of the first 192k. It is interesting that the most significant 4-bits of the data transfer is showing incorrect in the two examples you show. Best to try the jumper first thing though I guess.

 

[Maverick1978]

Interesting... I have an EX with a ram card in it that works fine. Got an HX for $40 shipped off of ebay with a ram card and a surprise Plus->ISA cable (YAY!!) and it gives me similar errors (detects 640kb, then spits out hex codes similar to the OP's problem). I never got around to diagnosing further, or even looking for jumpers - have been way too busy since it arrived two weeks ago! Maybe I'll have to pull the HX out tonight and play with jumpers... I eventually plan to add an XT-IDE and an internal CF HD, however. I like all-in-one formfactors (it's the Commodore 8-bit guy in me!)

 

[Hatta]

Yes, I can confirm it was the jumper. Setting E2-E3 back to E1-E2 fixed my problem. Doh.

Maverick1978, if your computer is recognizing 640K it's probably not the same problem I had. Mine was set to 640K and threw errors because I only had 384K in it. If your screen reads 640K there probably is 640K in it, and you've just got some bad drams. That should be an easy fix.

I'm also doing the xtide/cf card thing. I've gotten as far as building the card and adaptor and seeing it boot up and load the bios. But the tandy doesn't seem to like powering the CF-IDE converter I bought. I adapted a 5v molex fan adaptor and hooked that up to the floppy drive's power supply. With just the adaptor plugged in it booted fine so there's no short or anything in the adaptor. But when I plug it into my CF-IDE converter, the LEDs on the converter light up, and the tandy tries to start, but I get garbage on the screen.

Is there a better place to tap 5V?

 

[geoffm3]

Yes, I can confirm it was the jumper. Setting E2-E3 back to E1-E2 fixed my problem. Doh.

Maverick1978, if your computer is recognizing 640K it's probably not the same problem I had. Mine was set to 640K and threw errors because I only had 384K in it. If your screen reads 640K there probably is 640K in it, and you've just got some bad drams. That should be an easy fix.

I'm also doing the xtide/cf card thing. I've gotten as far as building the card and adaptor and seeing it boot up and load the bios. But the tandy doesn't seem to like powering the CF-IDE converter I bought. I adapted a 5v molex fan adaptor and hooked that up to the floppy drive's power supply. With just the adaptor plugged in it booted fine so there's no short or anything in the adaptor. But when I plug it into my CF-IDE converter, the LEDs on the converter light up, and the tandy tries to start, but I get garbage on the screen.

Is there a better place to tap 5V?

I think on mine I tapped straight off of the power supply... I can't see far enough inside the case to tell. Are you sure that the card is configured correctly for the Tandy? Here's what I've been successfully using:

dips:
2,3,5,7,8 on

JP1 and JP2 jumpered
IRQ 2
K1 L

I have 640K RAM on my HX.

 

[Hatta]

I figured it out, it was a problem with the adaptor. Tried another one and it worked fine.

My setup appears to be fully functional now. All I have to do is squeeze it into the tiny EX case. Unfortunately, there's no empty drive bay as in the HX to mount the CF card. I'm debating whether to remove the 5.25" floppy drive and it in that bay, or to dremel out a slot on the left side under the keyboard.

I'd kind of like to keep the floppy drive, but I'd also like to avoid cutting the case. Not an easy decision.

 

[geoffm3]

I figured it out, it was a problem with the adaptor. Tried another one and it worked fine.

My setup appears to be fully functional now. All I have to do is squeeze it into the tiny EX case. Unfortunately, there's no empty drive bay as in the HX to mount the CF card. I'm debating whether to remove the 5.25" floppy drive and it in that bay, or to dremel out a slot on the left side under the keyboard.

I'd kind of like to keep the floppy drive, but I'd also like to avoid cutting the case. Not an easy decision.

In my case, I shoved the CF adapter into the cavity between the expansion bay and the keyboard just under the keyboard. The EX might be different though.

 

[Maverick1978]

Interesting... I have an EX with a ram card in it that works fine. Got an HX for $40 shipped off of ebay with a ram card and a surprise Plus->ISA cable (YAY!!) and it gives me similar errors (detects 640kb, then spits out hex codes similar to the OP's problem). I never got around to diagnosing further, or even looking for jumpers - have been way too busy since it arrived two weeks ago! Maybe I'll have to pull the HX out tonight and play with jumpers... I eventually plan to add an XT-IDE and an internal CF HD, however. I like all-in-one formfactors (it's the Commodore 8-bit guy in me!)

Just following up for future reference. The 640kb mem card in my EX was a Tandy original and works fine. The mem card in my HX is an unmarked 3rd-party card that has DMA (thankfully), and uses 4qty 10-pin DRAMs to provide 640kb. No jumpers on the card. One of the DRAMs was bad - process of elimination with a spare from the parts bin, and it's good to go.

 

[geoffm3]

Just following up for future reference. The 640kb mem card in my EX was a Tandy original and works fine. The mem card in my HX is an unmarked 3rd-party card that has DMA (thankfully), and uses 4qty 10-pin DRAMs to provide 640kb. No jumpers on the card. One of the DRAMs was bad - process of elimination with a spare from the parts bin, and it's good to go.

Interesting... I had o idea that any third parties made plus expansion cards, let alone a memory expansion card. I wonder who made it?

 

[Maverick1978]

Wish that I knew! There's no real identification marks on it. It uses 64-pin IDC connectors for the ISA edge and pin-side connectors. They've got a piece of some kind of non-conductive material jammed into the last two pins on the edge card to ensure that nothing can be inserted there, while the pin connector floats over the pins (unlike my Tandy model, there's no housing to seat the connector in - just 62 bare pins sticking up). I don't believe that the plus cable was home made - its crimps and ribbon lengths are too precise, and anyways why would a home user bother jamming non-conductive material in an edge connector to ensure that a card isn't inserted the right way? - there'd be no need; they crimped it and knew which way to put in the ISA card!

I'll see if I can get a picture up of it tonight.

 

[kb2syd]

Interesting... I had o idea that any third parties made plus expansion cards, let alone a memory expansion card. I wonder who made it?

Hard Drive Specialists was one company that made a few plus expansion cards. There was another here in NJ that did the EX/HX line and a few expansions for the peanut.