Compaq Portable 286 and Portable III - IDE drives?

Jules Richardson jules.richardson99 at
Fri Mar 3 16:33:52 CST 2017

On 03/03/2017 03:08 PM, Fred Cisin via cctalk wrote:
> On Fri, 3 Mar 2017, Jules Richardson via cctalk wrote:
>> Just checking here, as someone told me that this is the case, but do the
>> Compaq Portable 286 and Portable III take stock 40-pin IDE hard drives? I
>> just wanted to make sure that they weren't expecting something that might
>> be a bit non-standard before I go trying to find modern replacements for
>> a pair of failing disks.
> I think so, but I also think that Compaq's IDE was before it was completely
> standardized, so there might be some glitches.

Yes, that's my concern. I thought it may even be expecting something like 
XTA, but I suppose that doesn't really make sense given the '286 or '386 
CPU (I only picked up the Portable III last weekend and I'm not sure which 
CPU it has - I believe that the later ones had the '386)

> 1) If you are going period OS, get Compaq MS-DOS V3.31.  Anything prior to
> that is limited to 32MB per partition.

Well, I suspect 32MB will be plenty :-)

I don't think I've ever actually tried putting a large-capacity IDE disk 
into a machine which was designed for something much smaller (I've always 
had a stash of period drives kicking around in case of failure). I'm not 
sure if it all gets translated into a linear address somewhere between 
system and drive anyway[1], so I can pretty much pick any BIOS drive type 
and expect it to just work (obviously at massively-reduced capacity!), or 
if the drive really is addressed via CHS and so I need to pick type[2] 
carefully (or look into LLF).

[1] And I know that I used to know the answer to things like that, but it 
all fell out of my head years ago :-(

[2] Maybe picking something that's "smaller in all dimensions" works, 
though? It would waste some enormous number of sectors on each track, but 
that's not really an issue if it works!

> 2) You may want to use a "disk manager overlay" to be able to use specs
> other than the BIOS ones:

Aha, some useful info there - thanks!




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