Commodore 1541 disk drives

Commodore had produced a 5.25 inch disk drive for the VIC 20, the VIC 1540. This however did not work with the 64 because of timing problems, so the 1541 was introduced with a revised ROM. Both the 1540 and 1541 were unusual in having their own onboard operating system and memory. The disk drive connects to the serial port making data transmission slow. Up to four can be daisy-chained together and a printer can be added provided it is at the end of the chain. Each drive needs to have its own device number, from 08 to 11, the default being 08. This can be changed by software or, as in the case of my K 0014427, the hardware can be permanently changed. The 1541 is heavy due to having a built-in power supply and becomes very warm in operation.

Rear View

The disk drive connects to the serial port. Up to four can be daisy-chained together and a printer can be added provided it is at the end of the chain.

My 1541s



Serial 501808 (Japan)	Serial 5023962 (Japan)	Serial DA5 087538 (W.Germany)
VIC-1541	Awaiting repair	Awaiting repair



Serial DA5 092088 (West Germany)	Serial DA5 119799 (W.Germany)	Serial K 0001563 (Japan)



	Serial K 0014427 (Japan)		Serial AA5018320 (Japan)
	Converted to drive 09		Cream to match the 64C
	One of my original pair from 1983		and with a lever lock

The 1541's user manual is complicated and confusing and there are errors in the instructions. This is not helped by the fact that both the VIC and the 64 use Basic 2.0 which has no drive commands. The drive itself has problems too. The worst of these is the "save@" option. This should allow a file or program to be altered and then resaved to disk. However, if the new version is longer than the original it is cut short. The solution is to rename the old version, then save the new version and only delete the original once the resave has been checked.

Another, potentially expensive, problem is that the drive head forgets where it is. To rectify this it moves as far to the side as it can, banging against the side to make sure it can go no further. This is the rat-a-tat-tat sound you get when you format a disk. Eventually this can cause the head to go out of alignment making reading and writing disks impossible. Many software houses used this "error" to protect disks from being copied, even the Easyscript disk supplied with the 1541. It was concern about this that caused me to write my own word processor.

Commodore 1541-II Disk Drive serial number HB5 112824 made in Hong Kong.

The 1541 Mark 2 was introduced in 1988. It has an external power supply and a smaller footprint. Disk operation is quieter and smoother than the 1541. The case has a lighter colour to match the 64C.

Rear View

The device number can easily be changed as required (with the drive turned off!) using the two dip switches at the back of the 1541-II. Disk drives can be any number from 08 to 11.

Off

On	On

08

	On
Off
09

On
	Off
10


Off	Off
11

My Mk-II 1541 Drives



Serial BLS 075021 (Hong Kong)	Serial HB5 034265 (China)	Serial HB5 083561 (China)



Serial HB5 112824 (Hong Kong)	Serial HB5 267988 (China)

Commodore 4040 serial WG 2357 made in W.Germany.

Commodore 8050 serial M4002163 made in USA.

While the Datassette tape deck was the first storage device bought by most PET owners, a disk drive was much faster and more suited to business users. Commodore produced a range of dual drives, taking the new 5¼ inch disks. Earlier disks had been a massive eight inches, so the 5¼ inch ones were called diskettes.

While the 4040 and the 1541 can read each others disks, BASIC programs load to different addresses on different computers. In general disks, drives and computers cannot be swapped. Most later drives used the serial interface.

I have a second 8050 (M4009754). These three drives connect using an IEEE-488 cable with a special plug on the end that fits the edge connector at the back of the PET. A printer could be attached to the disk drive using a standard IEEE-488 cable.

Commodore 1551 serial AD4 004969 made in Japan.

Commodore 1570 serial DA5 15055 made in W.Germany.

Suitable for the Plus/4, the 1551 connects to the user port instead of the more usual (for Commodore) serial port. It has the same style of case as the 1541 rather than that of the 1541-II. Since the 1551 could only be used with the Plus/4, most people used the 1541 or the 1541-II.

Designed for the 128, the 1570 was a temporary solution to the as yet unready 1571. Still, most people stuck with the 1541 and the 1541-II as these were readily available and could be used with other Commodores.

Commodore 1571 serial DA5 53575 made in W.Germany.

Commodore 1581 serial 00564 made in Taiwan.

This was the top of the range disk drive for the 128 and 128D. Capable of faster speeds, greater density and using double sided disks. An internal power supply but does not get as warm as other models.

Unusual for 8 bit Commodores, a 3.5 inch disk drive. Works with the 64 but is more suited to the 128 and 128D. On sale from 1987, the 1581 is much smaller than any other Commodore disk drive.

Oceanic OC-118N serial 1028550 made in Taiwan.

A substitute for the 1541 and other drives, the Oceanic disk drive is smaller and lighter. Third party hardware was rather limited due to protectionist action by Commodore.

The 1551 connects to the user port instead of the more usual (for Commodore) serial port. The rear of the plug has a connector for more devices.

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