JDR MCT 8-bit IDE controller

[modem7]

The card has jumpers for 2 KB and 8 KB, and 2 KB is the factory default. So maybe the ROM is only 2 K in size?

In regard to the jumper you write of, JP4, I see that the manual does not indicate the function of the jumper.
I see that page 1-3 of the manual indicates that the default address range for the ROM BIOS is C8000 to C9FFF, i.e. 8 KB sized.
And if the image of the BIOS ROM that mikey99 posted is examined, it is not a 2 KB block that has been repeated three times (i.e. code size is greater than 2 KB).

EDIT: You're right, the BIOS ends with a cut off string.

Per [here], in the file that mikey99 posted, I do not see a partial string just prior to offset 1800h.

It looks like the area after the BIOS is actually RAM. The BIOS appears to be storing variables in offset 1Cxxh (beyond the 7 KB boundary).

Is the situation perhaps:
* 8 KB ROM fitted, with first 6 KB containing BIOS expansion code.
* Card maps into motherboard memory space only the first 6 KB of the ROM.
* Card contains one or more RAM chips.
* With JP4 set to its default value of 2KB, card maps 2 KB of the card's RAM from address [ROM base + 6KB] onwards. JP4 can increase that to 8KB (perhaps requiring additional RAM to be fitted to the card).

Using DEBUG, can you successfully write/read values to [ROM base + 6KB] ?

 

[erikarn]

hm, what's the RAM being used for? Has anyone figured out?

 

[vwestlife]

Mine has ROM version 3.3. MSD's Memory Browser reports it as 6 KB in size. It has separate messages for 8086/8088 and 286+ systems, although mine still shows the 8086 message even when used with a 286 system. It also suggests there should be a way to manually define the drive parameters, but I don't know how to access that -- the normal DEBUG g=c800:5 command doesn't work. And I don't know if the CI-1010 was a typo or a reference to a previous model.

 

[Krille]

Per [here], in the file that mikey99 posted, I do not see a partial string just prior to offset 1800h.

Yeah, I made a mistake when removing the header. The string is not cut off.

Is the situation perhaps:
* 8 KB ROM fitted, with first 6 KB containing BIOS expansion code.
* Card maps into motherboard memory space only the first 6 KB of the ROM.
* Card contains one or more RAM chips.
* With JP4 set to its default value of 2KB, card maps 2 KB of the card's RAM from address [ROM base + 6KB] onwards. JP4 can increase that to 8KB (perhaps requiring additional RAM to be fitted to the card).

Yes, looking at the image of the card at the beginning of the thread there's a Goldstar GM76C28A-10 chip which is a 2 KB SRAM. You can replace that with an 8 KB chip (and move the JP4 jumper) to get an additional 6 KB RAM in the UMA. I don't know what the BIOS will do when/if it detects the additional RAM - probably nothing. It doesn't seem to use that much of the 2 KB RAM to begin with. My guess is that you can probably use that extra 6 KB as a block of UMB memory with something like USE!UMBS.SYS.