Jiffydos VIC 20 PAL and Jiffydos 1541 ?

[Overdoc]

Hi VIC fans,

I am wondering if a PAL VIC-20 with Jiffydos installed (PAL version) will actually work together flawlessly with a 1541 drive with Jiffydos installed as well?

Afaik a PAL VIC-20 runs roughly 25% faster than a PAL C64, so therefore the 1540 has a different rom with correct timing for the VIC20.
So when I use Jiffydos in a VIC-20, I would think that I also need to have Jiffydos installed in the 1540?
But: There is no Jiffydos for the 1540, only for the 1541!

I know the 1541 can also be switched to 1540 mode with U- command.
And I think a 1541 also works together flawlessly with a VIC-20 even when not switched into 1540 mode?

But, will this also be true when VIC-20 and 1541 are running Jiffydos instead of the original kernal & rom system?
Or will I always need to switch the 1541 into 1540 mode with U- command whenever I want to use it with the VIC-20 ?

Thanks for any light on this

[eslapion]

Hi VIC fans,

I am wondering if a PAL VIC-20 with Jiffydos installed (PAL version) will actually work together flawlessly with a 1541 drive with Jiffydos installed as well?

SInce I have this very configuration right here, I can tell you it does work.

JiffyDOS is a protocol which operates on a completely different timing scheme compared to the normal CBM DOS so comparing with the 1540 vs 1541 speed is completely irrelevant.

The 1541 and 1540 are essentially the same drive with a slight slow down activated on the CBM DOS to ensure compatibility with the C64 which has CPU cycles stolen by the VIC-II.

As you pointed out yourself, the VIC-20 will work fine with a 1541, whether this slow down is activated or not.

There is no JiffyDOS for the 1540 because it uses the same JiffyDOS as the 1541.

[Overdoc]

Hi Eslapion,

Great
Thanks for the explanation and confirmation that it works.

[eslapion]

@Overdoc

Please note the difference in speed between the 1541 and the 1540 (or 1541 with slow down disabled) is only about 10%.

A 1541/1540 with JiffyDOS will load about 5 times faster than a normal 1541 speed but this is really limited by the amount of RAM in the drive and/or the sector interleave on the diskette from which you are loading.

You get to experience the full potential of the protocol when loading from a drive like the 1581 or SD2IEC. The extra RAM they have allows the protocol to transfer data with much less interruptions. The result is transfer rates about 12 times the speed of a standard 1541.