1541 with demo's fastloaders

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1541 with demo's fastloaders

Francesco Messineo
Hi all,
I have recently repaired a few 1541s (various revisions, various
mechanics) and I've found a quite strange situation with one VC-1541
from 1983. It has a short board with quite some wire patches on the
solder side (they look quite well made, so I think it's as it come out
from the manufacturer). This unit was modified with the speeddos
parallel cable and I removed the mod since I didn't need it. The
mechanics was still almost perfect, it needed just a good cleaning,
after an easy electronic fix, the 1541 was reading and writing quite
well.
I usually test a few demos that use quite optimized fastloaders to
make sure all is well with the drive before declaring it "good".
My favourite demos are Lunatico from LFT, which uses a very clever
fastloader, it's described in his blog, I really recommend reading how
it works as it uses also 6502's unofficial opcodes and other clever
tricks.
However, this particular drive worked well with the LFT's demo.
Then I've tried the Concert demo from Performers and the drive showed
a quite an unexpected behavior: it seemed slow like the fastloader
didn't work, but the demo progressed into the third disk anyway and
just before the concert part (if anyone is familiar with this demo, it
hangs after loading the "rock me amadeus" cover part. I'm sure the
disk is good and anyway this 1541 reads the disk fine when I try to
copy it.
Now I suspect some tricks in the Concert demo hit a particular hidden
fault of this drive.
I'll try a different 6522 on UC3, most old speeddos mods tend to
damage that chip.

So the question: does anyone know how this fastloader work?
I'd rather not disassemble a whole demo :)

Thanks
Frank

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Re: 1541 with demo's fastloaders

MiaM
Den Wed, 6 Jun 2018 10:44:45 +0200 skrev Francesco Messineo
<[hidden email]>:
> Hi all,

I'm not sure if this is related, but there are known cases of demo fast
loaders that doesen't work on a 1541C with it's track 0 detection
circuit and firmware.


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Re: 1541 with demo's fastloaders

Francesco Messineo
Hi Mia,

On Thu, Jun 7, 2018 at 2:31 PM, Mia Magnusson <[hidden email]> wrote:
> Den Wed, 6 Jun 2018 10:44:45 +0200 skrev Francesco Messineo
> <[hidden email]>:
>> Hi all,
>
> I'm not sure if this is related, but there are known cases of demo fast
> loaders that doesen't work on a 1541C with it's track 0 detection
> circuit and firmware.

well... I've just tried LFT's Lunatico on a 1541C with -001 firmware
and track 0 detection enabled, and it works fine ;)
The issue with the other 1541 was probably very slightly marginal
media. I copied the third disk on another media with a standard
whole-disk copy program (not particularly fast) and with the same 1541
and now the copy works fine, works fast and goes until the end.
So the first disk was good enough at standard speed but failed with
the fastloader, interesting :)
BTW, also Concert demo works fine on the 1541C with track 0 detection.
Regards
Frank

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Re: 1541 with demo's fastloaders

traymond160
Try Maverik Data copier it's fast.
I believe Tim Harris in the UK bought the rights to Maverick copiers and theĀ 
Ramboard.
The Ramboard along with the Ramboard nibbler, you can slow the drive speedĀ 
to read longer tracks etc, hidden data.
Of course for your own personal backups of commercial games.

If you need Tims contact info just let me know.

Terry Raymond


On Thu, Jun 7, 2018, 9:07 AM Francesco Messineo <[hidden email]> wrote:
Hi Mia,

On Thu, Jun 7, 2018 at 2:31 PM, Mia Magnusson <[hidden email]> wrote:
> Den Wed, 6 Jun 2018 10:44:45 +0200 skrev Francesco Messineo
> <[hidden email]>:
>> Hi all,
>
> I'm not sure if this is related, but there are known cases of demo fast
> loaders that doesen't work on a 1541C with it's track 0 detection
> circuit and firmware.

well... I've just tried LFT's Lunatico on a 1541C with -001 firmware
and track 0 detection enabled, and it works fine ;)
The issue with the other 1541 was probably very slightly marginal
media. I copied the third disk on another media with a standard
whole-disk copy program (not particularly fast) and with the same 1541
and now the copy works fine, works fast and goes until the end.
So the first disk was good enough at standard speed but failed with
the fastloader, interesting :)
BTW, also Concert demo works fine on the 1541C with track 0 detection.
Regards
Frank