Blue Chip BCD/5.25 Disk Drive

After previously dissecting the firmware of alternate C64 disk drives, let’s now look at the hardware of one: This is the Blue Chip BCD/5.25.

The BCD/5.25 is a clone of the 1541. Its hardware is equivalent to the Commodore 1541, and it even uses an obfuscated version of that drive’s firmware.

My device came in the original box. It was bought at Sears for $179.99 (in 1986).

  • Works with Commodore 64 and 128, SX64, C15, Plus 4, and VIC 20.
  • 100% Compatible with Commodore Computers
  • Runs 1000’s of programs written for Commodore
  • Faster, More Accurare, and Less Expensive than Commodore.
  • BLUE CHIP ELECTRONICS, INC. • 7305 W. BOSTON AVE • CHANDLER, AZ 85226 • (602) 961-1485

  • Commodore Interface. 100% Compatible with the Commodore 64, Commodore 128, SX16, C16, Plus 4, and VIC 20. The cable’s included free.
  • Rugged construction. Virtually bulletproof. Fully shielded, high impact case. Comes with a Full Year Warranty.
  • Mass Data Storage. Stores over 174,000 bytes and 144 separate directory entries per diskette.
  • Key Latch. A lightly engineered precision disk centering system guarantees exact disk positioning everytime. State-of-the-art Ceramic heads, and a steel band positioner eliminate almost all read/write errors.
  • External Power Supply. Because the power supply is outside the drive, the BCD/5.25 runs 24 hours a day without overheating. (No more lost programs because your disk drive got too hott!)
  • Compact Size. The BCD/5.25 takes up a lot less space than the Commodore drive. (And because it’s more efficient…it’s also less expensive.)
  • Software Compatible. Runs 1,000’s of programs written for Commodore. Works with almost everything. You name it. Games, Wordprocessors, Spread Sheets, Education packages.
  • Easy to read panel indicators tell status of the drive at a glance. Built-in “Power On Diagnostics” included!
  • State-of-the-art ceramic read0write heads for long life and trouble free operation.

Interface: Commodore compatible, dual serial port with daisy chain option
Number of Tracks: 35
Number of Heads: One
Data Encoding Method: Group Coded Recording (GCR)
Net Weight: 3 lbs. 12 oz.
Capacity: 174,848 bytes per diskette. Total.
168,656 per diskette with Sequeltial Files.
167,132 bytes per diskette with Relative Files.
Buffer Memory: 2048 bytes
Track Density: 48 Tracks per inch.
Directory Entries: 144
Sectors per Side: 17 to 21
Bytes per Sector: 256
Blocks per Side: 683
Internal Write Protection: Yes
Power On Diagnostics: Yes
Power Consumption: 15 Watts (Typical)
Power Supply: External – 16 VAC 0.8 Amps
9 VAC 1.5 Amps
Power Requirements: 120 VAC, 60Hz.
Dimensions: 3.0″ x 6.75″ x 10.6″
Reliability: Mean Time Between Failure (MTBF) 10,000 Power-on hours
Media Requirements Industry Standard (ANSI) 5 1/4″ diskettes; soft sectored
Warranty: One year. Parts and Labor
Compatible Computers: Commodore 64, Commodore 128, SX64, Plus 4, C16, and VIC 20

The label on the front panel says “BLUE CHIP 5.25 DISK DRIVE”. Surprisingly, the lever opens to the left.

On the back, there is a power switch, a proprietary power connector and two Serial connectors.

The power supply (Model No. 108-138) outputs 16V and 9V. It is possible mod the drive to work with a 1541-II power supply (12V and 5V), though.

The board contains
* UC7: 2 KB SRAM (SRM2016C)
* UD1/UD2: Two 6522 VIAs by UMC
* UD3: A 6502 CPU marked “N 3065”, with a date code of 8622.

It is unknown who made this 6502, I’ve never seen one with these markings.

These are the mechanics, from the top…

…and from the bottom.


6 thoughts on “Blue Chip BCD/5.25 Disk Drive”

  1. Fun fact: The power supply spec, including the connector and it’s pinouts is identical to the power supply for Spectravideo 318 and 328.

    Recently (last couple of weeks) there has been successfully 3D printed replicas of the cable connector, so the shortage of suitable power supply connectors should finally be solved.

  2. Because Blue Chip and other third-party drives use real (if obfuscated) ROMs, does that mean that they are 100% compatible with the 1541 (or at least as compatible as the 1571 is)?

  3. You articles on Commodore peripherals prompted me to retrieve my old VIC-1520 colour plotter from the attic at my mother’s house. I used it in the 80s to do plots for my physics practicals. It was working when it went into the attic but I no longer have a C64 to test it with. I really need to take some nice pictures of it and scan the manual.

  4. I have also seen N3065 used in the Chinese Education Computer, a Chinese clone of Apple IIe.

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