XTs and large hard disks

[Tony Duell]

> 
> 
> > Hi everyone!
> > 
> > I have an old Portable PC that I put a 2MB memory card in, along with an EGA
> > card, sound card, and some other stuff.  I'm doing my best to max it out.
> > Anyway, I'm having some trouble with hard disks.  I have two hard disk
> > controllers: a Seagate ST02 SCSI/Floppy controller, and a Juko Labs D16-X
> > IDE controller.  Now both of these cards work okay, except they recognize
> > some strange sizes for the disks.  The only disk that seems to show up
> > correctly is a Quantum LP105S...the others I tried, all bigger than a gig,
> > are either not recognized, or recognized with the wrong size.  This is also
> > the case with the IDE controller - everything is recognized at 10MB.  I
> > purchased an LBA PRO card for my machine hoping to overcome the large disk
> > size problem, but all it does is freeze the machine...however, if I remove
> > the 8088 and replace it with a NEC V20, I get the banner for the hard disk
> > drive card, and THEN the machine freezes.
> > 
> > So my questions are: 
> > 1. Does anyone know a good solution for putting a large drive in an XT,
> > while still leaving it an XT?
> > 2. Should I leave the V20 in?  I've heard it has compatibility issues with
> > some programs, but I'm not solid on my information.
> > 
> > Regards,
> > 
> > Julian
> 
> This particlar can't handle this large due to decoding issues or 
> capacity issues (1GB is too large for 8088 than needed), either the 
> XT is a shoddy clone the TTL timings is not right if using a firmware 
> add on to handle large IDE capacities.

Hang on a second, this is an XT. In fact I assume 'Portable PC' means the 
IBM 5155, which has a real IBM XT motherboard in there.

The motherboard BIOS on an XT does not support hard disks at all. The 
hard disk drivers are in an extension ROM, conventionally placed on the 
hard disk controller card. So if a particualr card won't support large 
drives, it's an issue with the firmware on that card, not with the 
motherboard BIOS.

> The SCSI is best for this if stuck with 8088.  Otherwise keep under 
> 500MB with IDE, not even 540, have to be under 500.  Is the portable 
> standard XT or baby AT layout?  Go with 286 or 386DX then everything 
> else will work as described.  There are many 286 and 386 boards that 
> has XT mounting holes layouts.  Choose carefully, there are so many 
> junk out there.

The problem with this is that the keyboard interface changed between the 
XT and AT. And you pretty much have to stick with the original XT 
keyboard on a 5155...

-tony