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In this follow-up to my IBM PC AT restoration, I dive into the legendary hard drive issues that plagued early models—including the infamous CMI drive failures. My AT came with a Seagate ST-4026, but getting it to work wasn’t as simple as plugging it in. After replacing capacitors on the disk controller, battling BIOS errors, and running a painstaking low-level format, I thought the drive was dead—until I discovered my own wiring mistake! Join me as I troubleshoot, learn from my mistakes, and finally bring this classic machine back to life with IBM PC DOS 3.3.
00:00 Intro
00:52 The IBM PC AT Troubled Hard Drive History
04:18 Repairing the IBM PC AT Disk Controller
05:28 IBM PC BIOS: Configuring the Hard Drive
07:04 Drive Inspection & Diagnostics
07:38 Will a Low-level Format Fix It?
09:44 Root Cause: Wrong Cabling
12:10 Installing IBM PC DOS 3.30
14:16 Performance Gain with Sector Interleaving
16:49 Conclusion / Next on TPC
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This video was made possible with support by:
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Alisha Manuale Stutz @alishamanuelastutz
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Copyright @ 2025 THE PHINTAGE COLLECTOR, Gianpaolo Del Matto. All rights reserved.
Individual Copyrights apply for referenced material (see links).
Theme Music composed by Abdallah El-Ghannam.
https://www.fiverr.com/abdallahghannam
Additional music featured by
rootkitty: https://soundcloud.com/rootkitty
Links:
Original PC references:
https://en.wikipedia.org/wiki/IBM_Personal_Computer_XT
https://en.wikipedia.org/wiki/IBM_Personal_Computer_AT
PC AT Add-in Cards, Mainboard and Diagnostics Information:
https://minuszerodegrees.net/5170/cards/5170_cards.htm
About Computer Memories (CMI):
https://en.wikipedia.org/wiki/Computer_Memories,_Inc.
https://minuszerodegrees.net/5170/cmi_6426_problems/IBM%205170%20-%206426%20problems.htm
About ST-412/506 and ESDI:
https://en.wikipedia.org/wiki/ST-506/ST-412
https://en.wikipedia.org/wiki/Enhanced_Small_Disk_Interface
https://minuszerodegrees.net/5170/hdd/5170_hard_drive_cabling_single_twisted.jpg
IBM Disk Adapter:
https://minuszerodegrees.net/5170/cards/5170_cards.htm#fddda_
About MFM, Sector Interleaving:
https://en.wikipedia.org/wiki/Modified_frequency_modulation
https://en.wikipedia.org/wiki/Interleaving_(disk_storage)
PC Error Codes, PC Hardware Reference:
http://ps-2.kev009.com/pcpartnerinfo/ctstips/49fe.htm
https://retrocomputerverzamelaar.nl/wp-content/uploads/2016/12/IBM-PC-Hardware-Reference.pdf