View Full Version : Tandy project

March 18th, 2012, 03:01 PM
With my other 2 projects on hold waiting for parts, i am attempting to figure out something with my tandy 1000Rlx-HD
It's maxed out 1mb on main board and all, if i were to add an ems card to it, i have a ems board that may fit in, would i be able to allocate the EMS while it has the extended memory in it? I have PC-DOS 2000 Rev 1 setup so it sees the remaining 384kb left over as extended, but if the tandy can only address 1mb, how can it see the 384kb as extended?, can i keep that setup as extended, AND have the ems board? Would i be able to use the ems board for things like qram without hindering the extended memory? My goal here is to get it to have more than 1mb ram, which i think it can do, but some trickery is needed to do so. So before i waste my time, is that even possible? Or would i be asking too much out of the old hardware.

Great Hierophant
March 18th, 2012, 08:11 PM
That 384K is mapped as extended memory, above the 1MB addressing space. A 286 can address 16MB, but because there are no address lines 21-24 on an 8-bit slot, you are stuck with the amount Tandy sought fit to put on the motherboard. So, there is no barrier to you using an EMS board with a D000 page frame. With an RSX, the max was 9MB on the motherboard, even though the 386SX can address 16MB. Although the system has 16-bit slots, the RAM access would incur a tremendous speed hit.