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Gettin UMB space 640k-1024k on a tandy computer.

So far as I know in an SL the potential space for UMBs is going to be from C000-DFFF, because they have the E-page and up occupied with ROM. Remember, if you have an XTIDE/hard disk controller/whatever that uses an option ROM that's going to subtract from the available space.

An HX normally has the same limitations, with E-and-up filled with DOS and Personal Deskmate resources. Per my recent thread in the Radio Shack section with hacking I was able to override those resources and open the E000 page for RAM/EMS and replace the built-in DOS at F000 with the XTIDE option ROM. That means a contiguous 192k of upper memory space is possible even with a mass storage device available.

I've thought about offering copies of the board I'm doing this with for sale, but my impression was that the itch for HX expansion boards had already been scratched, at least for casual "gamer" applications.
 
soviet9922 said:
How much UMB space where you able to get ?
Click to expand...

Because the Lo-Tech IMB board is only configurable in 64K chunks starting at the beginning of each segment address, I was only able to get 64K on my Tandy 1000 SL. The C000 address block was used for the XT-IDE BIOS. On my SX I was able to get 192K of total upper memory at A000-AFFF, D000-DFFF & E000-EFFF. Again the XT-IDE was configured to use the address space starting at C000.
 
jasa1063 said:
Because the Lo-Tech IMB board is only configurable in 64K chunks starting at the beginning of each segment address, I was only able to get 64K on my Tandy 1000 SL. The C000 address block was used for the XT-IDE BIOS.
Click to expand...

How much memory space does your XTIDE card assign to the BIOS chip, and does it allow you to set the starting address to C000? If you're willing to hack the Lo-Tech card slightly you could probably give yourself the top half of the C-page in addition to D without a lot of work.
 
Eudimorphodon said:
How much memory space does your XTIDE card assign to the BIOS chip, and does it allow you to set the starting address to C000? If you're willing to hack the Lo-Tech card slightly you could probably give yourself the top half of the C-page in addition to D without a lot of work.
Click to expand...

Alas my XT-IDE card is also a Lo-Tech and only 2 addresses are configurable via a jumper C800 & D800. Not a big deal as DOS, TSRs and drivers all load into the 64K block with a little to spare.
 
jasa1063 said:
Alas my XT-IDE card is also a Lo-Tech and only 2 addresses are configurable via a jumper C800 & D800. Not a big deal as DOS, TSRs and drivers all load into the 64K block with a little to spare.
Click to expand...

Out of curiosity, what version of DOS are you running? With PCDOS 7 if I only have 64k of UMB I get a message that there's not enough memory free to load SYSTEM high, so only data and drivers make it into upper memory. (I wonder if it's a consequence of the tweaking to load DOS data high and it effectively "beats" DOS itself to too much of the available UMB, or some other IBM dos peculiarity.)...

Hrm. Thinking about it, I am *pretty* sure I was able to fit DOS 5 into 64k. It's been a while.

96k seems to be about a sweet spot for me, because that fits everything including DOSKey, mouse drivers, etc, and the packet driver for my network card.
 
Eudimorphodon said:
Out of curiosity, what version of DOS are you running? With PCDOS 7 if I only have 64k of UMB I get a message that there's not enough memory free to load SYSTEM high, so only data and drivers make it into upper memory. (I wonder if it's a consequence of the tweaking to load DOS data high and it effectively "beats" DOS itself to too much of the available UMB, or some other IBM dos peculiarity.)...

Hrm. Thinking about it, I am *pretty* sure I was able to fit DOS 5 into 64k. It's been a while.

96k seems to be about a sweet spot for me, because that fits everything including DOSKey, mouse drivers, etc, and the packet driver for my network card.
Click to expand...

I am using DOS 5.0, with USE!UMBS.SYS, DOSMAX.EXE, NANSI.SYS, CTMOUSE.EXE and 4DOS 8.0. I don't have a network card installed, if I did 64K would definitely not be enough.
 
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