First post, by megatron-uk
I thought I'd document my experiences so far with trying to get large IDE devices (>500Mb, unsupported by BIOS types 1-46) working on older machines (primarily, what I've found so far for my 286 build).
Hardware I'm using:
8GB 133x Transcend CF card
CF to IDE adapter
286 motherboard, BIOS supported drives type 1-47
Basic 16bit ISA multi-io controller, no onboard BIOS
Possible solutions that may work:
Option 1. Replace multi-io card with an IDE controller with onboard BIOS. Eg Promise EIDEMax.
The ISA controllers with onboard BIOS should support drives up to 8GB - I've not seen any yet with LBA support, but that's not to say there aren't any. They're still around on Ebay every now and then. Downsides are that you lose another 16bit ISA slot and you have to be careful with plug-and-play designs that you cannot easily change their resources.
Option 2. Replace your existing BIOS with another one that supports drives up to 8GB. Eg the XTIDE project has BIOS releases for AT class machines that do just this.
The BIOS can be added to a number of ISA cards (that don't even need to be IDE controllers) as long as the BIOS is socketable or flashable. The software is actively developed and has a number of nice functions and a nice configuration tool. Downside is that unless your existing multi-io card has a BIOS (unlikely) you still lose a 8 or 16bit ISA slot to whatever controller you add to host the XTIDE BIOS.
I will try this option with my SCSI controller as the BIOS is socketed - I just need to pad the 8kb rom out to fit a 27c128.
Option 3. Use a modern(ish) ISA SCSI controller and SCSI to IDE bridge solution.
This should enable you to use big(ger) IDE disks, up to the size supported by the SCSI controller (at least 8GB on most Adaptec chipsets) and also gets the benefit of DMA transfers on supported cards. Downside is (as I've found with my particular SCSI-IDE bridge) that not all combinations work. The main SCSI-IDE bridges are the IO-Data R-IDSC (which is the one I'm using), the Acard AEC-7720 and one from Yamaha that was bundled with a CD/DVD writer. The AEC-7720 is the best, but also very expensive (like entirely new computer expensive).
I have tried this but my motherboard seems to have issues with a) the DMA transfer of the AHA-1542, and b) detecting anything hanging from the SCS-IDE bridge. To be fair, I had the latter problem when I tried to use the bridge in a towered Amiga 1200.
Option 4. Drive Overlay Software / Disk Translation Software.
In theory the drive overlay software can be used to access the full capacity of a disk even if the BIOS doesn't.
I have tried the following drive overlay software so far:
Maxtor Maxblast 3 (Ontrack 9.56a)
Boots into a custom Caldera DR-Dos system - config.sys needs editing on my 286 class machine as it has a call to DOS=HIGH,UMB that fails - it then boots to either a graphical or text mode (selectable). Detects the full capacity of the Transcend 8GB CF drive and allows partitioning in either WIn98SE/FAT32 compatible single partition, or as earlier Dos/FAT16 multiple 2GB partitions.
Upon reboot the overlay software activates when the CF drive boots and prompts to insert a floppy to boot from (the CF drive is formatted when the software is installed/partitioned). At this point (with the Ontrack software loaded, the blue banner showing and prompting for a bootable drive) I cannot get any bootable floppies to work; they spin for a second or two but do not load. Leaving a floppy in to boot from instead of the CF drive boots from the floppy ok, but the CF drive is then an unsupported scheme/size, as one would expect.
Maxtor Maxblast 2
Boots into a custom Caldera DR-Dos system - config.sys needs editing on my 286 class machine as it has a call to DOS=HIGH,UMB that fails - it then boots to either a graphical or text mode (selectable). Hangs at the 'inspecting hardware' stage and goes no further.
Samsung Drive Manager
Requires a ramdrive bigger than the 3MB of XMS that my 4MB 286 provides in order to decompress working files into - the installation and setup do not complete. In addition the config.sys tries to load an XMS driver that is not compatible with my 286 (not himem.sys or himemx).
So what options do I have left? Well, I'm going to try the XTIDE BIOS route, by writing an eprom to go in the SCSI card (I'd already budgeted for one 16bit ISA slot to be used by the SCSI card, so I'm not losing anything there). That's the first option, as I can try this without any additional hardware or cost.
Secondly I'll see if there are any older versions of Ontrack that I can find, to see if they work any better (ie don't have the floppy boot problem).
Lastly, I can try tracking down a later ISA controller with onboard BIOS, to take over from the rudimentary IDE support in the 286 motherboard. This is the last option, as the cards are fairly expensive compared to what I've spent on the rest of the entire machine.
Anyone else had much fun getting larger drives working on XT/AT/286 type hardware?
My collection database and technical wiki: