1541 Speed Test (and more) released.

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Zibri
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1541 Speed Test (and more) released.

Post by Zibri »

Hello!
A few days ago I released 1541 Speed Test to help a few friends of mine to repair drives.
The program important features are:

1) it's the most accurate ever made and correctly shows speed with cent of rpm accuracy.
2) it has the fastest updates (more than 2 per second) allowing real time checking.
3) it has a big speed display, useful in packed laboratories :D

A very nice video tutorial is also available in italian language (but automatic subtitles with english translation seem to work pretty well).

The official and latest version can be always found here:
https://github.com/Zibri/C64-1541-Speed-Test
RPM.png
RPM.png (2.55 KiB) Viewed 234 times
RPM_F1.png
RPM_F1.png (1.41 KiB) Viewed 234 times
Please, read the instructions, because there are some more features.
Also know that the program writes on track #36 so don't use it on a disk containing data on that track.


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eslapion
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Re: 1541 Speed Test (and more) released.

Post by eslapion »

Track 36 is outside the normal BAM so I guess it's nothing to worry about if you only have a normally formatted floppy with just the test program on it.

I find it rather surprising that a reference disk isn't required. Could you tell us what your program does with track 36 to know the speed ?
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Re: 1541 Speed Test (and more) released.

Post by rmzalbar »

Does it write one sector or a sync mark, and then go to read mode and use the internal timer to calculate the interval between "sightings" as it spins around?
Zibri
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Re: 1541 Speed Test (and more) released.

Post by Zibri »

eslapion wrote: Sat Aug 29, 2020 2:41 am Track 36 is outside the normal BAM so I guess it's nothing to worry about if you only have a normally formatted floppy with just the test program on it.

I find it rather surprising that a reference disk isn't required. Could you tell us what your program does with track 36 to know the speed ?
Many program use this method:
They write $55 all over a track... and write a SYNC at the END like $FF $FF.
Then they use cia timers (wrongly by the way) to time the passing of the sync mark.
The problem is that to detect a SYNC mark the assembler code has a jitter of 7 cycles... which is too much to be accurate on a single spin.
So some of them even average with more rounds, but still they (all I have tested) have wrong calculations and hey jitter even using an emulated "perfect" drive.

Also in that case a reference disk is not needed!
rmzalbar wrote: Tue Sep 01, 2020 6:59 pm Does it write one sector or a sync mark, and then go to read mode and use the internal timer to calculate the interval between "sightings" as it spins around?
Not quite :D

My program anyway does a different thing, which might sound surprising:

It writes FF all over the track (any track will do) then it writes 5 bytes specially crafted $5A (which is a Z like Zibri) which happens to be a very good value:

01011010 01011010 01011010 01011010 01011010

after writing (which happens only once at the start of each test),
My program reads ONE byte then 5 MORE.
Wherever it starts it will make a full round (because there are 5 bytes).

Now the big difference is:

1) to read a byte, the "jitter" is only of 3 cycles over an average of 200 thousand cycles per round at 300 rpm.
2) all calculations on the cia timer are done correctly ;)

I also made a test program which looks and works in the same way and it DOES NOT write anything :D
It has the same accuracy!
And it only needs a DOS empty formatted disk.
The difference is that without writing a track the program "trusts" that you fully formatted a disk before testing.
I didn't see the point since in this case you need to format a full disk, while in the released version it just needs to write a track.
On the released "d64" image is also present a configuration program which will create a customized version.
Many aspects can be customized including the track to write (which is totally arbitrary).

I strongly suggest you to read the full instructions:
https://github.com/Zibri/C64-1541-Speed ... ctions.txt
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