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Zibri
Account closed
Registered: May 2020
Posts: 304 |
New life for your underloved datassette unit :D
The first phase of testing just ended.
(Still in the packaging and refining phase)
But I wish to share with you all my latest accomplishment.
You might want to check this out:
https://twitter.com/zibri/status/1450979434916417540
and this:
https://twitter.com/zibri/status/1450979005117644800
The fastest example (11 kilobit/sec) has the same (or better) error rlsilience as "turbo250" but it is 3 times faster.
The slowest one (8 kilobit/sec) has the same error resilience as the standard commodore slow "save", but it is 100 times faster and twice as fast as turbo250.
;)
Notes:
1) faster speeds are possible if the tape is written with a professional equipment or hi-fi with a stabilized speed and virtually no wobbling.
2) if the tape is emulated (tapuino or similar projects) the speed can go up to 34 kilobit/sec.
3) even with datassette, higher speeds are possible but the highly depend on the status of the tape, the datassette speed and azimuth. |
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Frantic
Registered: Mar 2003
Posts: 1648 |
Quote: LOL! no, but if you want to come to Sharm El Sheikh I'll show you what a paradise is here :D
A random girl at Twitter just started a thread about "worst place you've travelled to", and her own suggestion was precisely Sharm El Sheikh, which she found really awful. Now of course I realise that people have different tastes, and personally I know nothing at all about Sharm El Sheikh — maybe it is totally great — but it was still kind of funny in relation to this thread. Hehhe..
Aaaanyway... back to topic and keep up the good work on those loaders! I'm eager to see what comes out of it. Maybe I should get myself a datasette again after all, just to be able to load real quick. :D |
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Neo-Rio
Account closed
Registered: Jan 2004
Posts: 63 |
Quote: Quoting Neo-Rio
I have a TDK D90, and a Maxell UE 90, and the TDK one allows for high speed mastering. I did all Zibri's testing with the TDK tape.
Just for curiosity (I don't expect "much" difference but some, yes) did you try my tests on the "bad" tape? It would be interesting a comparison on that too. ;)
No I never did any of your tests on the bad tapes. I don't think there'd be much point.
One of the decks had occasional trouble getting to FOUND without distortion creeping in one in every five or so attempts - and that's before it even reached the tape turbo!
I could give it a go anyway, but I would not be expecting miracles! These tapes are only good for people who like their music with snakes hissing as backup singers. :D |
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Zibri
Account closed
Registered: May 2020
Posts: 304 |
Quoting Neo-RioNo I never did any of your tests on the bad tapes. I don't think there'd be much point.
One of the decks had occasional trouble getting to FOUND without distortion creeping in one in every five or so attempts - and that's before it even reached the tape turbo!
Oh.. then it's very bad, because everything before the lines start is in standard commodore format (like any other normal save)
Also, note, I gave you test files, they have redundant data on them and if you want to compare speeds or counter clicks you should compare from when the "thin" lines start and not before that. In the final version everything before that will be way shorter.
Also note: I made a big calculation error on the last files I gave you. I sent you the updated ones. I was very tired yesterday, it always happens after swimming and taking sun :D
Sorry for wasting some of your time.
And thanks again for the tests. |
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Zibri
Account closed
Registered: May 2020
Posts: 304 |
Quoting FranticA random girl at Twitter just started a thread about "worst place you've travelled to", and her own suggestion was precisely Sharm El Sheikh, which she found really awful. Now of course I realise that people have different tastes, and personally I know nothing at all about Sharm El Sheikh — maybe it is totally great — but it was still kind of funny in relation to this thread. Hehhe..
Yeah.. sure.. I have enought money to live anywhere and I chose the worst place because I am a masochist :D sure.
Many people have horrible holidays here because they go cheap and trust shady travel agencies or go to bad resorts.
I live here full time since 6 years. And it's paradise.
(Unless you like snow, and cold weather, then is hell)
Quote:
Aaaanyway... back to topic and keep up the good work on those loaders! I'm eager to see what comes out of it. Maybe I should get myself a datasette again after all, just to be able to load real quick. :D
ehehe.. the 1541 thanks to the great works of Krill is unbeatable. Internally it uses 26 to 32 microseconds per bit and even considering GCR format that goes at 32.5 to 40 microseconds per bit. That is the equivalent of 25000 to 30769 Hz. which is 3 times what the datassette can handle.
The datassette amplifier has a filter cutting everything above 11Khz (barely detected at 12khz)
An interesting thing of the datassette, anyhow, is that you can directly control it from the C64, while on the 1541 you have to use the IEC bus which is the bottleneck.
Thanks to krill and realtime GCR and 2 bit transfer that is less "felt" but still... |
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Neo-Rio
Account closed
Registered: Jan 2004
Posts: 63 |
While it's relatively easy to align your equipment and master your own tapes for your own use, it's another thing entirely to master a tape with no fancy equipment other than the C2N and then spread warez (lol) to other datasettes - and have the programs load without issue. And then do it on a deck that has probably never been serviced, and has a drive belt that is 30 years old and worn out!
To do this test, I kept the same TDK D90 and had one C2N master the tape, so the other could read it.
Makes absolutely no sense in this day and age to master to garbage tapes for general consumption, and a 90 minute cassette is a borderline length for normal use.
I am simulating the average CBM C2N deck out there and stuck in someone's loft with my CBM deck that has never been serviced, or had it's alignment adjusted. In many ways it is dialing down my test speeds considerably to reach that happy sweet spot where the loader should work on most anything within a user serviceable context.
So my CBM had issues with speeds under 18, and even with 18 had a glitch on loading the very tape it mastered until I tried and second time and it got it right. Interestingly loading the tape on my much newer clone deck presented no issue, but without a doubt, my clone deck is better for making tape masters.
I think Zibri's table is more or less accurate. 18 is the bleeding edge of reliable (if you can tolerate the occasional load failure), 19 may be the sweet spot, and 20 should be rock solid even on a mistreated C2N you found in a car boot sale.
That said, 16 is a reasonably reliable speed for well serviced units and self-made masters you only intend to read for yourself.
According to Zibri and all the dumps I've sent him to analyse, my old CBM deck has a lot of wobble and that's probably down to the worn-out drive belt. I may just hunt down a replacement and see if that helps in the reliability stakes. I guess it makes sense that anyone still using a datasette TODAY get a replacement square belt (75-80mm L x 1-1.2mm W seems to be about the right dimensions), and get rid of any 30 year old belt that's had it's day.
Anyway, we'll see if any improvements need to be made yet, and I'm sure there's more testing to do. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
That brings us back to the question how c2n hardware is specd regarding wow and flutter (wobble) :) |
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Neo-Rio
Account closed
Registered: Jan 2004
Posts: 63 |
Quote: That brings us back to the question how c2n hardware is specd regarding wow and flutter (wobble) :)
And I don't suppose Commodore ever documented this - other than in software?
Software that carried two copies of the data and took forever to load... ?
Did third party software houses ever receive support from Commodore for mastering tapes en masse, or was it simply a wild west? |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
Not Commodore - but the vendors of the tape mechanics surely did this. Commodores implementation surely is based on the specs of the tape mechanics used in the 2001 PET, and then was just reused again and again. |
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Zibri
Account closed
Registered: May 2020
Posts: 304 |
Update: turns out that because of a previous version comment in the code, my program was OFF by a lot of cycles (and still performed).
After the correction of the typo, the program gave STELLAR RESULTS.... showing all his accuracy...
The program was working also before... but the results I was given didn't "add up" to what they whould have been.
I worked on it a night and the files were perfect.
The loader wasn't :D
It's parametric, and I was calculating wrongly it's parameters :D
Now I can finally say that unless another loader will use my same method, I will always be able to match it and surpass it.
P.S.
I created a program that checks 62K of memory and loads at $801 to FFF0.
Then it checks all memory with a simple 16 bit XOR on all bytes BELOW the ROMS and BELOW SID, VIC and CIAs chips.
The resulting prg works if loaded from ultimate or vice monitor or from some custom loader (like giana sisters).
If you want the file, it's here:
https://github.com/Zibri/C64/raw/master/chkram.prg
To load it in VICE just go to the monitor and write
l"chkram.prg" 0
x
then from c64 you can just do RUN
the file contains just "urandom" data and the data is checked in the range 0800-FF00
I can do a version that checks from 0500 to FF00 if that's not enough... my loader will load that too.. |
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Neo-Rio
Account closed
Registered: Jan 2004
Posts: 63 |
I continue to play with these loaders and I think the difference between them is something akin to arguing over VHS and betamax.
My current reliability test has me using a TDK D90 to master a TAP in my newish aligned clone deck (which is capable of running Zibri's at it's master 15-6 setting - which even then isn't as accurate as professional hi-fi equipment or a CUTE32), and then trying to get that master to load in my CBM deck - which has never been serviced EVER - and work three times in a row without a single failure.
With the latest RC of slushload:
0x0c - had a single failure, so it's probably not as reliable as I first thought
0x0d - passed all three loads, and on the fourth load I shook the datasette around and only then did it fail
0x0e - passed and resisted abuse
Which makes 0x0e probably the best setting for general DIY mastering on decent tapes for distribution.
With Zibri's loader:
I've been trying his 21-14 setting and it failed the test, but his 24-24 setting worked fine. Note that there are two settings on Zibri's so more possible combinations of loads that are going to be reliable and those that aren't. The settings probably need more tuning for my crap deck, and it's not as fast obviously. Zibri is adamant that his loader be used on well maintained equipment and his code is more tunable than is Slushloads. Also this means that he can probably master a tape so well that it will be incredibly hard to copy with the old dual decks trick. If it was 1984 he might be showered in cash from EA or some other publisher.
So while it seems that Zibri's is the fastest, hands down - it's reliability is fairly limited to well maintained equipment - like betamax.
Slushload is not as fast, but comes across to me as fast enough with less reliable equipment - like VHS.
And really - speeds between the two? there's not much between them. A counter turn or so. Slushload however needs to stop cheating with the shorter tape lead in, as it's causing my old CBM deck lots of problems picking up FOUND and even loading in the first place.
Now I have absolutely no technical understanding of what I am currently seeing. I'm not digging into anyone's code. I've just been sitting around making masters and seeing the results for the past couple of days.
Well, that's the state of play so far - and I'm just one person's opinion and review. Everything is subject to change as both codebases aren't even finished yet.
What is for certain is that Gyrospeed has been surpassed. |
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