💾 Archived View for uscoffings.net › retro-computing › systems › Tandy › t › t1kems.txt captured on 2023-01-29 at 05:46:08.
⬅️ Previous capture (2022-06-04)
-=-=-=-=-=-=-
Sb: #EMS 4.0 board
Fm: Jack Amrol 73760,2726
To: all
This is to let anyone interested in this subject know how I am progressing so
far. I finally got the Invisible EMS board physically installed in my Tandy
1000sx the other night. I temporarily pulled the hard disk controller so I
could see what I was doing, and it went right in. The screw hole doesn't line
up, so I'll use that as an excuse for my previous problems.
I am pleased with this board. It is a true HARDWARE 4.0 EMS board, at least as
far as I know it.
I think it might work in OTHER 1000's better than in the sx. Actually, I think
it might work better in an sx with another video card (VGA or EGA).
Here is my SWAG as to what's going on in this thing.
1. By means(sp.?) of a jumper you tell it whether it has
384 or 640k. The video adapter then sets up 16k for itself
at the 370 or 624 mark. Therefore, if you wanted to disable
down as low as you could, you can only disable down to 384
(128 goes to video adapter and then to cpu, 256 goes to
the DMA chip otherwise the cpu would have to handle all
I/O calls etc).BUT there's the Tandy gotcha. The backfill
should be CONTINUOUS! The 16k video at 370-384k stops this.
IOW, when jumpered at 384, that is exactly what you and DOS
will get!
When jumpered to 640k, you can backfill, but you can't get
the extra up to 7??k, again because because it must be con-
tinuous. Right now I am backfilling to 384. I have it jumpered
at 640, AND I have 640 installed! I don't think I want to trust
any important data to that particular memory area. When I pulled
the chips that take care of 385-640, and left the jumper OFF,
(telling it to expect 640) and backfilling, I got a lot of
memory errors, as you would expect.
2. My 286 express card (or something) must set up some kind of
space at E400, because the EMS card just didn't like it, or
more likely it checks for a 286 cpu and expects some ROM to
be there.
3. XMS memory isn't possible with the express card, since it
boots up on the 8088 (expected, but hey you know I tried!).
All in all, the card itself performs like a champ. I loaded about 30k worth of
drivers into the A000-FFFF region. It definitely is capable of enhanced EMS.
BTW, don't buy QRAM for this card, because you won't need it. It comes with
it's own version of LOADHI (com. and sys.) and I don't think any of you would
like the performance penalties you get with files and buffers in the upper
memory.
I said upper memory for a reason. Quartedeck and Invisible seem to agree on
some things and not on others. Desqview definitely sees the board. It's been a
lot of fun playing with it, going from one program to another. In playing with
it under the many configurations, I've had some horrendous crashes (why? take
your pick of 3 or 4 reasons). I tend to think maybe my 8k cache (for the 286
card) gets overwritten every once and a while. Anyone out there surprised?
Anyway what one company calls shadow ram, the other calls something different,
but both use for the same thing (filling in A000-FFFF with RAM and then putting
TSR's and drivers there), but neither one will recognize it if made by the
other's program.
My verdict- Good Board-Just what I was looking for. Doesn't work well with MY
system. Might work even for me if I had VGA or a board with it's own memory.
Might work for other 1000's that have the video disabled. Got a good workout
inside the box, pulled a few things out, put them back in-tried not to sweat on
those 256k chips-found out how valuable a set of tweezers can be. BTW, the chip
extactor/installer doesn't work so good on re-installing chips since the pins
have already been bent in once, so it won't hold onto them. Had fun with x= i=
/r etc.
Jack Amrol
P.S. I have no idea if the last few lines are going to make it.
Invisible Software
415-570-5967
If you know what's good for you you won't mention my name. They were extremely
pleasant, helpful, and knowledgeable. Comes with 512k, 2 meg, or 8 meg.
-----------------------------
Fm: Dan Robins 70007,3264
To: Jack Amrol 73760,2726 (X)
Jack,
I didn't see it in your message...but what brand name is that board you
installed?
Dan
-----------------------------
Fm: Jack Amrol 73760,2726
To: Dan Robins 70007,3264 (X)
It is the Invisible EMS Board. It is 8/16 bit and comes with 512k, 2 meg, or 8
meg.
Vance Wu over in IBMHW is a VP of the company.
Phone is 415-570-6017
-----------------------------
Fm: Dan Robins 70007,3264
To: Jack Amrol 73760,2726 (X)
Jack,
Thanks for the info! Dan