A bit about IDE drives

IDE drives, also known as PATA drives are a dying breed.
Being superseded by SATA and M.2 this long-standing standard for hard drive interfaces has been discontinued for years now.

This poses a problem for vintage computer enthusiasts like myself as these drives are no longer being manufactured and the existing ones are starting to show their age.

To solve the problem with dying disks I have been searching for alternatives to using a real IDE harddisk in my vintage systems and, as it turns out, I am not alone in this quest.

After a lot of research on how the IDE interface works and what different variaties of it exist, 2 nagging problems popped up.
One is that IDE basically uses 2 transfer modes: Port I/O (PIO) or direct memory access (DMA). The former can either use interrupts or be polled which you could see as 2 modes as well.

The other one is that for a short period of time there also existed an interface known as XTA or XT-type IDE. This one really threw me off for a good while.

The challenge

If you’ve been reading this blog for a while you know that I have a couple of Toshiba T1000LE machines, both of which are classified as XT-type systems.
The harddrives in these can be used in either XT or AT mode.
I (wrongly) assumed the T1000LE used the drive in XT mode, as it is an XT system.
As it turns out, it uses the drives in AT mode, PIO mode 0 with interrupts.

So after solving that problem the next one arose: How do I replace drives in a machine that is very picky about the type and model of hard drive that is installed.
I still don’t know what exactly it is that the machine checks but it probably has something to do with either make/model or C/H/S parameters as it denies any IDE drive other than the original ones.

Now, for bigger systems, ones that have the possibility of adding an ISA expansion card like my T3200SX, there is a beautiful community-driven project called the XT-IDE Universal BIOS and the XT-IDE card. This basically allows you to use any modern IDE drive, CF card or even an SD card as an emulated XT harddisk.
This, obviously, won’t work in portables like my beloved laptops.

Back to research

After a lot of searching and asking around I found a project by Alan Hightower: The NetPi-IDE.
This awsome project was originally developed for the IBM PC-Jr to work in conjunction with the XT-IDE sidecar and is based on a CPLD and Raspberry Pi Zero.

Of course, this device wouldn’t simply fit in my laptops so I modified the PCB layout slightly, making it a bit more narrow.
I also added a 5V header so I could power it directly from the machine.

That’s it (for now)

I ordered all the parts I needed from DigiKey, some of them are on backorder and will take a month or 2 to arrive.
For other components I had to guess the values as they weren’t in the schematic so I hope those are correct.

I ordered 5 PCBs from JLCPCB, those should arive somewhere next week.

I hope this project can finally provide me with a working harddrive that I can plug in to my laptops. As a bonus, the NetPi-IDE project offers some neat DOS tools and the RasPi is accessible over WiFi so I can upload/modify hard drive images wirelessly.

So for now, that is it. I will make a video about this once I get all the parts and have a change to assemble and test everything.