• Please review our updated Terms and Rules here

Load Dos high on a 486 Tandy 1000 TX question

C

CompositeGamer

Experienced Member
Joined
Feb 16, 2008
Messages
53
I have installed a 286 to 486 chip in a Tandy TX and would like to know if i can load dos high with version MS dos 6.22.

Can i do this if i install some sort of memory expansion board?

Does ems memory provide dos high?

DOS 3.3 gives me enough memory left over for my programs and DOS 6.22 loaded low won't.

i have also installed a 2 GB hardrive with large partitions and Dos 3.3 won't access these partitions.

any help on this will be great
 
Last edited:
How much memory do you have in your system currently? If it's over 1MB, you should be able to load it high. If not, you need more memory. Also, "standard" MS-DOS is somewhat finicky on Tandys. Try an IBM PC-DOS version, perhaps 7.1.
 
From what I understand the Tandy 1000TX is an XT like machine with an 80286 chip. So no extended memory. High memory comes from the first 64k after 1MB. I think there is no possible way for you to have high memory on this machine. But, you can use UMBs. UMBs are the spaces in the upper 384k of the 1MB addressable by your system. How much memory you can get from UMBs will depend on how many adapter ROMs you have installed. There are two ways to get UMBs. On a regular 640k XT you can simply replace the 64k RAM chips with 256k RAM chips, or you can install a LIM 4.0 EMS card. Both will require a 3rd party software tool like QRAM to convert the UMBs into usable memory. But, I don't believe you can use EMS and UMBs at the same time.
 
Maybe if you load DOS=HIGH, UMB it won't report any errors, but I bet if you examine the memory available to DOS you will find 0k high memory. It is impossible to have high memory on a system with only 20bit memory addressing.
 
I second that. If the machine can't physically add memory above the 1MB mark, then by definition high memory is not available.

The motherboard and the expansion bus would have to have more than 20 address lines to be able to put extended memory in the system. The high memory area is actually part of extended memory. (It is the first 64K after the 1MB boundary.) If this machine really is an XT clone with a 286 to improve the speed, then it doesn't have the wiring.
 
So i guess my system motherboard probably will not support loading dos above 640k even though theres a 486 chip present.

I was thinking it might be a possability if there is an memory expansion card installed.

Back in the 1990s i had an old memory expansion card installed on a computer and was able to use that memory as high memory (using himem.sys). I can't remember what CPU/motherboard it was but it probably was not an XT class.

My tandy has 768k of memory installed but the extra memory above 640k is for the video controller only. So i have a 640k system.

My tandy's only internal harddrive (scsi) has 500mb partitions that dos 3.3 won't use and it would be a benefit to be able to access the drive, load dos 6.2 and scsi drivers above the 640k.

Thanks for the info
 
Last edited:
Hmm, perhaps you missed what I said about the UMBs, so I will repeat again. You can infact get DOS to recognise system memory above 640k in an XT class system by adding an EMS board and a software driver. I think perhaps you are confusing "upper" memory with "high memory". Upper memory is made up of UMBs and HIGH memory. UMBs are free memory blocks that exist between 640k and 1MB, and HIGH memory is the first ~64k after 1MB. AT systems are capable of using both UMBs and HIGH memory, where XT systems are limited to just the former. I have heard of people doing 736k memory mods to both PCjr and Tandy1000 systems so it is definitely possible.
 
I guess i don't know much about memory things and i should narrow my questions.

Can i load dos or device drivers into the UMB area ?

Does having a 486 chip installed benefit my tandy as far as getting dos to load above 640k ?

I haven't got an EMS card but would like try one soon.

Read somewhere that EMS cards are mainly used for windows,lotus 123 or programs that are EMS specific.

Just haven't seen much info on the net about EMS cards and using them to load dos into the area above 640k.
 
Last edited:
Oh, I definetly agree. It's not easy to find information on the topic, but the newsgroups are probably the best place to try.

In my opinion having the 486 chip installed in your system should help making UMBs available. At least, that is the behaviour of installing an improve-it technologys make-it 486 into my IBM AT. But in order to do so on your Tandy you will need to have some memory above 640k physically installed on your system. You have indicated that your system has 768k installed, however 1MB would be ideal in order to get more free memory blocks. Since you only have 3 memory banks in your motherboard, you would need to use an EMS card to fill the remaining 256k...and perhaps not all EMS cards can be configured to do this "backfilling", but I think all LIM 4.0 boards should.

But, since you already have 768k installed, I think that you should test it out and see if you can make any of the UMBs available by loading EMM386 and set DOS=UMB in your system configuration files. You might want to consider 3rd party memory managers as well (ie The Last Byte) as they might be able to make better use of the UMBs.
 
I did try to load dos 6.22 above the 640k by adding the DOS=HIGH,UMB a few years back and it didn't work.

The tandy uses the extra memory for the video only and dosn't offer any for the user to use, as far as i know. This extra memory is the extra ram installed on the motherboard.

I will definitly have to get some sort of ems board to brink the memory above 640k.

I am appreciating all this info im getting, thanks
 
Last edited:
See Microsoft article 72926 - "Upper Memory Managers for 8086, 8088, or 80286 Computers"
http://support.microsoft.com/kb/72926

One of the memory managers quoted is QRAM:

Quarterdeck QRAM version 2.0

A memory manager for 8088 through 80286 machines. QRAM will provide UMBs (Upper Memory Blocks, memory greater than 640K but less than 1024K). To do this requires either LIM EMS 4.0, EEMS, a memory management chip or a 286 motherboard with C&T's NEAT, LEAP or SCAT chip set.
The UMBs can be used to load TSRs, device drivers, and DOS data structures into high memory in order to gain conventional memory for large programs.
 
Ah...the SCAT. There couldn't be a worse name for a motherboard/chipset.

Since you already have a 486 chip installed, I am not sure if you need to use QRAM or not. Certainly for the 768k on the motherboard EMM386 will do, but I am not sure if EMM386 will be able to see the RAM on an EMS board or not. QRAM may be necessary if you use a LIM4.0 board.

Tandy graphics can't use all of the extra 128k. I believe there is a utility that allows you to adjust the memory size. Allocating more than 32kb is for most purposes useless. You should try making the graphics memory smaller to see if you can free up some UMB memory.

Also, make sure everything in your system config files is loaded in the correct order. If you do it in the wrong order you won't get the UMBs. The DOS= statement should come AFTER you load EMM386 (or other memory manager). Also, for your DOS= statement, you should remove the "HIGH", it will have no effect since you only have 20 address lines. Save yourself the 5 bytes of memory and just do DOS=UMB.

*UPDATE*

I just found this rather interesting tidbit in the newsgroups:

"On the 1000RLX, there is a real 286 in there. And, like the 1000TX and TLx
series, the bus has been hog-tied to 8 bits to cut costs while allowing
the end-user to expand the machine. Since the HD, memory, and VGA support
are on the motherboard, the designers must have thought the only expansion
items would be low-performance add-ons like modems, hand-scanners, CDROMs,
etc... Lets face it, 150Kb/sec is not a problem on the 8-bit bus... If
you want to add SCSI or ESDI or 16-bit LAN cards to a 1000-series machine,
you are putting a big gas tank and tires on a Hyundai; get an *AT* clone!


Here's where I get fuzzier: I think that the 1000RLX had 1Mb of DRAM on
the motherboard and there was a setup option to remap the 384Kb of extra
high-memory in the 640K-1Mb region to above 1Mb. I believe it had a PS/2
mouse port (interchangable with the kbd) and the keyboard controller had
PS/2-style A20 support. This would allow the PS/2-style HIMEM.SYS A20-
handling to work. Try adding the following line to your config.sys and
see what it says (don't forget to tell SETUP to read CONFIG.SYS off the
boot device!):


device=C:\DOS\HIMEM.SYS /machine:ps2"

I am wondering if the MMU of your 486SLC chip has the ability to remap the memory between 640k and 1MB like in the 1000RLX. If so, this article implies high memory may infact be possible.
 
Last edited:
You must log in or register to reply here.
Back
Top