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Setting Up XT-IDE (dual drive)
Like my IBM PC 5150 setup (here), I used another XT-IDE to emulate “fixed disk” storage on the system. But due to the 5-bay limit of the 5150, I kept to a single CF-emulated fixed disk.
For dual fixed disks, recall there is a jumper on the XT-IDE extension for this purpose. I even borrowed the 40-pin PATA (“Parallel ATA”) HDD ribbon cable that was originally used in this system to connect between the main XT-IDE card and the IDE extension (and then also a Molex to 4-pin “mini”-Molex adapter for power).
NOTE: The reason for the white-paper is because I was concerned about metal pin-contact between the XT-IDE extension and the serial card below it. Just “an abundance of caution” in case those cards get flexed for some reason. The cards are bolted down tight in their expansion slot, so it shouldn’t be an issue, but these are horizontally mounted cards rather than vertical, so I just wanted to be cautious.
NOTE: The “MASTER/SLAVE” jumper is just turned sideways, just to keep it stored in case we ever want to change it back to MASTER instead of SLAVE. The other end of the 40-pin IDE cable goes into the main XT-IDE card (not the system motherboard).
BELOW: Image of the 8-bit ISA slots before inserting the XT-IDE expansion card. This side of the vertical “expansion tree” has two 8-bit ISA slots, while the other (more accessible) side has 3x 16-bit ISA slots. Also, image of the AT-style power connectors, replaced RTC clock, and AT-style keyboard connector.
NOTE: In my experience, the XT-IDE makes it unnecessary to really worry about the CMOS/BIOS configuration of the hard drive (the “Type 47” stuff). The software in the XT-IDE essentially hooks into the system and provides an easier and more robust detection of the hardware, so it “just works.” In addition, you’ll notice that during bootup, if you want to boot from either A: or B: drive you can just press A or B during the bootup of the system (the XT-IDE will detect this and highlight the selected drive, and then proceed to reading a disk in that selected drive). This can be used to temporarily override the default of booting to C: drive. You do need to set the MASTER/SLAVE jumper appropriately, but you won’t have to worry about specifying number of heads, cylinders, sectors, etc.
If you ever do want to work with a physical drive, the HEADS, CYLINDER, SECTOR information is typically on the label of the hard drive itself. In the example below, it is 16383 cylinders, 16 heads, 63 sectors (this particular IBM Travelstar is 18.1GB capacity at a slow-but-reliable 4200RPM). Typically, you would have to go into the BIOS, select “hard drive type 47” (user defined type) and enter in this information (which is then saved to the CMOS, if the battery is working). But not every chipset firmware supported this, and throughout the 1990s it was spotty on how large of a partition your setup would support. There isn’t rock solid advice on this, since it depends on the firmware version and the OS version involved. This is why it is good to keep around 2GB or smaller SD-cards, CF-cards, or physical drives (since in the early 1990s that was the general max capacity at the time).
Most physical drives will have 4-pins on one side, used to set the PRIMARY/SECONDARY setting if using multiple IDE drives along the same ribbon cable. The drives shown here are 2.5″ hard drives generally used in laptops, while desktops had larger 3.5″ hard drives.
There are ways to adapt more modern SD-card, mSATA, and M.2 solid state drives to these old IDE interfaces. Search eBay for something like “mSATA to IDE SSD adapter” or “solid state to IDE adapter.” Available for both 2.5″ and 3.5″ sizes. There is a lot of left over mSATA stock, a technology and interface that became popular around 2012 by generally replaced by M.2 cards.
In the above is a 2.5″ IDE / mSATA adapter. The mSATA size is a great fit for this application. There is also an example of a 2.5″ to 3.5″ adapter, allowing laptop IDE drivers to be used in desktop size cases.
Some related notes:
- The old ATA-IDE interface will be a bottleneck for performance, but the solid state devices will be silent.
- I have seen some of the mSATA and adapter cards get extremely hot. Take care, especially in a laptop that maybe doesn’t have a lot of ventilation (and depended more on the enclosure itself being a heatsink).
- Do not expect modern large-capacity solid state storage to work. Recall MS-DOS gradually increased the size of fixed-disk storage it supported over time. There is no easy/singular answer on what capacity will work, as it depends on the firmware of the system involved. But as time moves on, it is harder to find smaller 2GB solid state solutions. You may still be able to partition the device to have the max capacity, and then maybe create multiple partitions with any remaining space (or just waste it, e.g. a 128GB device maybe can still provide a 2GB boot partition).
While the XT-IDE is not period correct, I’ve had classic-mechanical hard drives crash on me in the past and it is not fun – so I consider it a reasonable compromise. There is something to be said about the original hard-disk mechanical spinning noise, where you could verify activity just based on the spin-up sound of the hard drive platters (or hear it “thrashing” in between game load scenes). Solid-state mass storage was not common in the 1990s. Some early digital cameras did offer a form of solid-state (likely either CompactFlash, or Sony had a Memory Stick). But the know-how to make a processor that bridged these over to IDE wasn’t there yet, so I don’t think any of them were bootable devices. The idea of a “solid state” RAM can be found in the bubble memory from around 1980 (see here on a system that used bootable bubble memory cartridges), so the merits of “silent computing” had been considered.