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Need help identifing a memory board (ISA 16bit) from Tandy

freakedenough

freakedenough

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Hi, does any of you know how much memory is actually installed on this board (I assume 1MB) and how to configure the Switches?
It was/is installed in a Compaq Portable 386 ISA Expansion and the Portable counted its 2mb of 32bit RAM fast and then the 16bit ISA RAM way slower and showed me 3MB of total RAM.
Unfortunately I accidentally touched the Switches while removing the card for cleaning the Portable, now it is no longer recognized. Compaq counts only its own 2MB of RAM.
However, I found this entry in TH99 which looks much like my card but if I configure it for 1MB and "Memory in Bank 1 enabled" it's still not recognized. Switch 1 to ON causes my Portable to not POST at all.



Thank you in advance for your help.
 
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It's 2MB. You need 9 chips to provide the 9th parity bit.

As for getting the card to work without documentation, if you are very patient, you can just try all 256 combinations of DIP switches, rebooting between each change. You can narrow this down if you know/remember which DIP switches were not accidentally changed.

The fact that the card says "Tandy 1985" leads me to believe that it was a memory expansion intended for the Tandy 2000 computer, so the fact that it was installed and working in a contemporary system is very surprising. I could be wrong though.
 
Trixter said:
The fact that the card says "Tandy 1985" leads me to believe that it was a memory expansion intended for the Tandy 2000 computer, so the fact that it was installed and working in a contemporary system is very surprising. I could be wrong though.
Click to expand...

The 2000 had a completely different slot form-factor, so it couldn't be for that. It looks like it's "full AT height", when did the Tandy 3000 AT compatible come out? (Google suggests early 1986, but maybe Tandy had an AT-compatible memory card in the works as a parallel development.)

If it is the Tandy 250-4030 there's faxback documentation here. Interestingly the manuals don't even seem to mention the Tandy 3000, I wonder if it actually ended up in the catalog before they had an AT to sell with it.
 
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freakedenough said:
Hi, does any of you know how much memory is actually installed on this board (I assume 1MB) and how to configure the Switches?
It was/is installed in a Compaq Portable 386 ISA Expansion and the Portable counted its 2mb of 32bit RAM fast and then the 16bit ISA RAM way slower and showed me 3MB of total RAM.
Unfortunately I accidentally touched the Switches while removing the card for cleaning the Portable, now it is no longer recognized. Compaq counts only its own 2MB of RAM.
Click to expand...

It's interesting that it only counted to 3MB if your Compaq has 2MB built in. If the manual is to be believed this board has kind of stupid memory decoding, only decodable starting at the 1MB line. (IE, if you have two MB on the card it reads like you're stuck having to have it span from 1MB-3MB or 3MB-5MB, etc, you can't have it go from 2MB-4MB.) My suggestion would be to try:

S1/1=off
S1/2-4 = on, on, on
S1/5-6 = off, off
S1/7=???
S1/8=off

Configured like this it'll try to fill 1MB-3MB, it could simply be that the Portable gives its own memory priority over any RAM in an expansion slot that overlaps with it. It'd be preferable if the card could map from 2MB-4MB, but that doesn't seem to be an option.
 
Eudimorphodon said:
It's interesting that it only counted to 3MB if your Compaq has 2MB built in. If the manual is to be believed this board has kind of stupid memory decoding, only decodable starting at the 1MB line. (IE, if you have two MB on the card it reads like you're stuck having to have it span from 1MB-3MB or 3MB-5MB, etc, you can't have it go from 2MB-4MB.) My suggestion would be to try:

S1/1=off
S1/2-4 = on, on, on
S1/5-6 = off, off
S1/7=???
S1/8=off

Configured like this it'll try to fill 1MB-3MB, it could simply be that the Portable gives its own memory priority over any RAM in an expansion slot that overlaps with it. It'd be preferable if the card could map from 2MB-4MB, but that doesn't seem to be an option.
Click to expand...

You can use this procedure to figure out the setting:
https://www.vogons.org/viewtopic.php?f=46&t=62298
 
With Mem extension cards you have at least to set 2 things.
1 starting address, that is in fact the already installed MEM on the MBoard
2 Amount of MEM on the ext card it self.

And as you did, find a similar card of same maker, than you have a clou how switches are ment to be.
They have app. same configuration.

Rest is fiddeling around as mentioned in that great site VOGONS.org, Thanks for that link.
 
OK, you guy were probably right. The TH99 page seems to fit when it comes to the switches. However, this makes it clear for me that I cannot use this card any longer with the Portable 386 because it has no option to be jumpered at address 200000h, directly after the 2MB internal RAM. At address 300000h it is no longer recognized and at 100000h it steals (overlaps) 1MB of the 32bit RAM resulting in 3MB total.. Thanks for you help and tips! As always much appreciated.

My config is now:
SW1 OFF (ON => no POST)
SW2 ON (100000h)
SW3 ON (100000h)
SW4 ON (100000h)
SW5 OFF (=2MB)
SW6 OFF (=2MB)
SW7 ON (ON/OFF makes no visible difference)
SW8 OFF (BANK1 enabled)

Would be interesting if this card can work in a 8bit bus or iof it requires 16bit.
 
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It might be fairly trivial to hack the card to map at even addresses instead of odd (IE, go from 2mb-4mb), but without the schematics, or at least good look at the board, I can't tell you how specifically to go about it.
 
freakedenough said:
at 100000h it steals (overlaps) 1MB of the 32bit RAM resulting in 3MB total.
Click to expand...

This is just a guess, but I would *hazard* that the memory controller/bus circuitry in the Portable has a mechanism to disable the R/W lines to the ISA bus for any address regions that are occupied by the 32 bit RAM. (IE, yes, it's overlapping, but when it's in the overlapping area it's not actually getting enabled, read/writes are only going to the onboard memory.) The reason I suspect this is because of the significant speed differences you'd *probably* get errors during the memory test if they were actually overlapped *and conflicting*.

I suppose it's possible that it has a mechanism that works the other way, IE, if something's stuck on the bus overlapping with built-in memory the external device wins, but that would be moderately harder to implement. I guess to know for sure you'd need to work out some way of benchmarking specific regions of Extended memory. But, well, the point is that it's *probably* okay to use the card to give you your *one* megabyte extra memory if you don't have other options and that extra meg actually makes a difference.
 
vwestlife said:
The 1987 Tandy computer catalog (published in late 1986) lists the 25-4030 Memory Expansion Board as being for the Tandy 3000:

http://www.radioshackcatalogs.com/html/catalogs_extra/1987_rsc-17/h011.html
Click to expand...

Yeah, I'm sure that's what it was intended for, it's just a little odd the faxback doesn't specifically mention it. I mean, it is *technically* compatible with any AT so there's no reason they had to, just a strange omission. The 1986 date on the PCB does predate the 3000 showing up in the 1987 catalog so I did look at the '86 catalog to see if it might have snuck in as a generic "PC expansion" but, no, 1987 was its debut as well. I'm sure there's a good chance the early 3000s have 1986 dates stamped in them somewhere.
 
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