First post, by hpxca
Dear Vogons Folks,
I was building a 486 DX2-66 and I ran into the common 504MB BIOS limitation with respect drive space. I tried EZRAID (DDO) to get around it and while it works just fine I wanted to mess around with XT-IDE as well. I purchased an ISA ROM card..this one => https://www.ebay.ca/itm/333274274119 as opposed to flashing it onto a NIC.
My video ROM seems to be <= 32k in size so C800 and up seems to be free, so initially I put the XT-IDE option ROM there and booted up. The ROM was detected and executed with no issues and the primary IDE controller (which is on a Multibest Industries MBCTL-02) card was detected just fine. This card only has a single IDE controller and floppy controller on board. The hard drive is the primary master - there is no slave on the bus - and the system booted...all was well so far. The IDE controller on this board is configured in the standard primary IDE configuration with the base at 1F0h, IRQ 14.
The CD-ROM is a "vintage" 16X CD-ROM that I did a little refurbishment on, and it is connected as the secondary master to the CT2830 IDE controller with the jumpers configured to 170h, IRQ 15 given that there's only a single controller on the I/O card. Without the XT-IDE ROM installed, the CD-ROM driver always detects the CD-ROM at 170h, IRQ 15 and everything works properly.
With the XT-IDE ROM installed there is long wait (about 15-30 seconds) as XT-IDE tries to detect a secondary master, when it fails and says none detected, the system boots but the CD-ROM driver fails to find a CD-ROM drive at 170h IRQ 15. This happens about 99% of the time. About 1% of the time, there is a much shorter detection period (1-2 seconds), XT-IDE still says there's no secondary master, but the CD-ROM driver loads normally and the CD-ROM works. Note again the "working scenario" is very rare and even rarer to have it actually work on consecutive reboots.
Here is what I have tried with no success (the CD-ROM is either not found at all, or found only very rarely):
-I have reflashed the EEPROM several times with the most recent version of the XT-IDE AT BIOS:
1. I have disabled detection of the primary and secondary slaves (because there are none).
2. I have confirmed that the IRQs match and the base and control register addresses are correct for both channels.
3. I have tried 8-bit mode on the secondary IDE.
4. I have tried polling instead of interrupt mode on the secondary IDE.
5. I have tried using just 1 IDE controller in XT-IDE (if I do this, the CD-ROM on the secondary IDE has never worked).
6. XTIDECFG.COM never detects the secondary IDE controller if you try to auto-configure it.
7. I have moved the base address of XT-IDE from C800 to D000.
8. I have re-jumpered the sound card to move the IDE interface to 1E8h, IRQ11.
Without fail, the CD-ROM always works if the XT-IDE expansion ROM is removed.
I have a pretty low-end ECS Elitegroup 4913 motherboard and one of the limitations of this board is that it can only shadow the system BIOS ("F-Segment"), the "C-Segment" and the "E-Segment", but it does not say exactly how much memory it shadows in each of these segments anywhere (I even read the manual!). I'm wondering with the limitations of this board if this is even worth the effort if I can't shadow the ROM. I was hoping that C800 was covered by C-Segment, but, of course without know if it's just a single 16k segment or more I can't be sure. If it is just one segment then only part of the video ROM is shadowed anyway.
If anyone has any ideas on what else I could try with XT-IDE or how much memory is actually getting shadowed with these BIOS settings, it would be appreciated.
