XT-IDE  Rev 2

This is the second revision of the XT-IDE card produced by the Vintage Computer Forums (VCF),  not the first nor third revisions.

Main article

See the wiki styled information here at the VCF.

Changes from Rev 1

• 'Hi-speed' mode (A.K.A. 'Chuck mod') added.
• Optional provision of +5V to pin 20 on the IDE connector.  A jumper (P9) controls this.  For those CF-to-IDE adapters and DOMs that support this.
• If desired, a 28C256 type boot ROM can be used instead of a 28C64 type.  Jumpers control this.
• OPTIONAL FITMENT: Serial port for remote booting.
• OPTIONAL FITMENT: Molex power connector.  This is a power outlet.  If desired, run a lead from here to power your IDE device.

Optional serial port  (optional UART)

Intended for remote booting.  With two exceptions, the serial port is a 'normal' serial port.

1. The first exception is that the port operates 4 times faster than normal.  For example, if you ran some terminal emulation software, then within that software, set the port speed to 1200 baud, the port would actually operate at 4800 baud.
BTW: The 4 x speed comes about because the XT-IDE rev 2 card uses a 7.3728 Mhz crystal, rather than a standard 1.8432 one.

2. The second exception is that only two hardware handshaking (flow control) lines are implemented: RTS and CTS.  The DTR, DSR, RI and DCD lines are not implemented.


It is not normal to have an XT-IDE Rev 1 card in a 16-bit computer such as the IBM 5170.  Normally, for performance, a 16-bit IDE controller would be used (see bottom row of here).  But, if you are planning to add an XT-IDE Rev 2 card to an IBM 5170, be aware of an incompatibility between the XTIDE Universal BIOS and the 5170 motherboard's IBM BIOS ROMs:

* The result is corrupted reads of files (as evidenced by CRC comparisons).
* The degree/frequency of corruption is related the revision of the motherboard BIOS. There were three revisions. The more modern the revision, the less corruption.
* The symptom disappears entirely if the IBM motherboard BIOS is swapped out for a non-IBM one.


Circuit diagram

Kicad images   (8 pages)

Power connector - Jameco part 117568   (2 pages)