Commodore 1541 Firmware Variants

TheCorfiot

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Merlin & I were discussing the repair of one of the 1541 drives that was recycled recently and a possible faulty ROM aroused suspicion.

I offered to investigate with my working 1541 and took the top off for the 1st time in 15 years :blink:

And lo & behold there is a strange ROM adapter with a foreign ROM sat in my 1541....


I Thought it might be an idea to start a thread & gather some info from our well informed members regarding Hacks & Firmware variants that exist for the Commodore 1541 /70/71/81..etc

Anyone wish to shed some light chaps....

TC (y)
 

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Merlin

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Thanks TC.

Here are the ones I know about.

1540...... 325302-01
1540...... 325302-02
1541...... 901229-01
1541...... 901229-02
1541...... 901229-03
1541...... 901229-05
1541C.... 251968-01
1541C.....251968-02
1551...... 318008-01

(y)
 
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jvdbossc

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Could be totally of but mostly it is just something like jiffydos build in..

If you are in need of the electronics, I have a 1541 in the recycle bin, electronics only.. I could alway's swap chips with a working unit to check and send them for shipping only..

Probably soon on sale drives to, but that would not be economical because of shipping..
 

TheCorfiot

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A question for the brainy ones....;)

Why does the 1541 Have two separate ROMS - 8KBytes each, Mapped to two separate areas & not continuous...

TC :ninja:
 

Merlin

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I know! (I think....)

Doesn't one of these ROMs have a version of Commodore DOS on it, as these were 'smart' peripherals....?

That would make one a boot ROM and the other one the onboard OS...
 

MagerValp

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Why does the 1541 Have two separate ROMS - 8KBytes each, Mapped to two separate areas & not continuous...

They are continuous ($c000-$dfff + $e000-$ffff). The simple explanation is that for one reason or another 2 x 2364 were cheaper than a single 23128 at the time of design (1981 or possibly early 1982). The board was redesigned in 1984 (the 1541C), this time with a 23128, as presumably the price had dropped.
 

Merlin

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@ MagerValp

Does that mean that they are pin compatible with 2764 EPROMS?
 

jvdbossc

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One nice feature I alway's like to be proud off:

They don't need a computer to copy disks, if you have two one unit 8 and one unit 9, load some software on the 1541's, they are programmed as disk copy device, you can take the c64 away from them, and they'll handle one site in 20 seconds.

Should go over my old disk to find out what that program is called..

Don't know about the roms not that technical, I know they have the same CPU as the C64 in them.
 

Merlin

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@ jvdbossc

It's the good old 6502 that's in the C64 and also the 1541, mate......

(y)
 

AgentX

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Does that mean that they are pin compatible with 2764 EPROMS?
2764s are compatible with an adapter like the one in the pic. They are pretty easy to make (here is a really good resource on how to build one).

@TC: Lovin' the 'St. Tropez' edition C128 sneaking into the shot there :LOL:
 

xc8

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....
They don't need a computer to copy disks, if you have two one unit 8 and one unit 9, load some software on the 1541's, they are programmed as disk copy device, you can take the c64 away from them, and they'll handle one site in 20 seconds....


fast hack'em!! \o/

Chris
 
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