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Boca XT RAM Card on AT-286 machine

alejack12001

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Is it possible or not to get a EMS/LIM 4.0, Boca 8-bit (XT) memory expansion card to work in a 286 machine that has an 8-bit slot? I tried this without success on my 286 machine. There are eight possible address combinations. For @D000 or @E000, the possible addresses are 208, 218, 258, and 268 using the BREMM.SYS driver and coordinating with the board switch bank. According to CHECKIT there is a conflict @DC00 so that sort of eliminates the @D000 address range. However, @E000 to @F000 is wide open. When I boot the CONFIG.SYS, the driver will not trigger Frames at the given address using, for example DEVICE=C:\BOCA\BREMM @E000 208 . Of course, I tried the other addresses. I have pulled the board but before I consider a total loss, I wanted the forum’s feedback. OS is MSDOS 6.22.
 

maxtherabbit

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The original 5170 AT had the E segment of UMA hardwired to ROM sockets on the motherboard, as such many clone boards did not make this segment addressable on the ISA bus. That may be your issue. I'd suggest trying to move whatever ROM is currently at DC00 to the C segment after the video ROM.
 

modem7

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One has to careful when interpreting tools like CheckIt, Spotter, etc. For example, per what maxtherabbit wrote, E0000h to EFFFFh is used by the IBM 5170 (IBM AT) motherboard for optional ROM's (irrespective of whether or not such ROM's are fitted). When I run CheckIt 3 on my IBM 5170, CheckIt 3 reports C4000h to F0000h as "<nothing>". Ideally, CheckIt 3 should be detecting (via the motherboard BIOS) that it is running on an IBM 5170, and consequently reporting E0000h to EFFFFh as "Reserved by motherboard".
 

alejack12001

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One has to careful when interpreting tools like CheckIt, Spotter, etc. For example, per what maxtherabbit wrote, E0000h to EFFFFh is used by the IBM 5170 (IBM AT) motherboard for optional ROM's (irrespective of whether or not such ROM's are fitted). When I run CheckIt 3 on my IBM 5170, CheckIt 3 reports C4000h to F0000h as "<nothing>". Ideally, CheckIt 3 should be detecting (via the motherboard BIOS) that it is running on an IBM 5170, and consequently reporting E0000h to EFFFFh as "Reserved by motherboard".
For all of my summer 2022 postings, the motherboard has been a unbranded 286 that houses 5170 ROM's. I guess it's the 5170 ROM that assigns the addressing of the memory space. The 286 in question has an Adaptec SCSI controller card as it's hard drive that is not boot able. The machine boots from a floppy drive. I have always wished for a software that would take a snapshot of the memory stack so the user would know where the conflicts are of ROM'ed hardware. So, the conflict of the @D000 addresses is the SCSI controller ROM, which resides at DC00. Can the DC00 adress be relocated, I don't know. Your probably right about the @E000-F000 addresses being reserved rather than available.
 

maxtherabbit

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The ROM is irrelevant, the 5170 board is physically wired that way.

You can relocate the adaptec boot rom with either jumpers or dip switches depending on the exact card model. I'd suggest moving it to C800
 

alejack12001

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The ROM is irrelevant, the 5170 board is physically wired that way.

You can relocate the adaptec boot rom with either jumpers or dip switches depending on the exact card model. I'd suggest moving it to C800
Okay let me check into it and get back. Thank you for the advice.
 

alejack12001

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Settings for the AHA-1522 SCSI controller does allow the following settings by jumpers:
BIOS Addresses are adjustable with settings: c800, cc00, d800, dc00
AL port address 340-35e no jumper and 140-15e with jumper.
So it's worth a try to change the settings and then see if the Boca will work. I'll let you know.
 

Eudimorphodon

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The original 5170 AT had the E segment of UMA hardwired to ROM sockets on the motherboard, as such many clone boards did not make this segment addressable on the ISA bus.

FWIW, even if you had a clone board that didn’t decode E0000-EFFFF into sockets you’d still probably have issues trying to put an 8-bit card into that space because the standard ISA mechanism for determining whether to use 8 or 16 bit memory operations is qualified on 128k boundaries.

I would note the other proviso that putting the 8-bit EMS card in the system might force you to set a jumper on your VGA card if it supports 16 bit ROM access to make it use 8-bit instead, but I think the BIOS chip on your SCSI card is probably also 8-bit already. (Don’t know for sure but a picture of the card makes it look like it’s a single 8-bit ROM.)
 

alejack12001

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FWIW, even if you had a clone board that didn’t decode E0000-EFFFF into sockets you’d still probably have issues trying to put an 8-bit card into that space because the standard ISA mechanism for determining whether to use 8 or 16 bit memory operations is qualified on 128k boundaries.

I would note the other proviso that putting the 8-bit EMS card in the system might force you to set a jumper on your VGA card if it supports 16 bit ROM access to make it use 8-bit instead, but I think the BIOS chip on your SCSI card is probably also 8-bit already. (Don’t know for sure but a picture of the card makes it look like it’s a single 8-bit ROM.)
I just switched from an 8-bit video card to 16-bit to possibly upscale the video from 640x400 to 800x600. The slot where the 8-bit video card resided is now freed up to take the 8-bit EMS card.

Using the suggested change by maxtherabbit, in the way the SCSI controller is recognized from the motherboard by changing the addresses; may free up space where the EMS card can be triggered from the BREMM.SYS. On the on-other-hand the 128k limit may cause it to hang. I'll have to see and report if the address change is successful or not.
 

alejack12001

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I said I would respond regarding the change to the FD/HD controller address setting from DC00 to C800. I found first that the available memory did increase, however, when I triggered the BREMM.sys the software was rejected again. with the configuration looking like DEVICE=C:\BOCA\BREMM.SYS @D000 208 and with the error stating that the software was not initiated. Basically as maxtherabiit said in an earlier statement that the available memory is actually reserved. I apreciate your help here, I guess were done here.
 
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