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2022.06.03 added links to LisaList1 and LisaFAQ to the General Category

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Author Topic: A Wee Cristmas Present  (Read 356 times)

Al Kossow

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Re: A Wee Cristmas Present
« Reply #15 on: December 29, 2022, 02:29:56 pm »

I think I found the lisa basic sources
UL'd to http://bitsavers.org/pdf/apple/lisa/pascal_monitor/floppy

you can browse and extract the files with applesauce. you don't need the hardware to do that
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stepleton

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Re: A Wee Cristmas Present
« Reply #16 on: December 29, 2022, 09:41:01 pm »

The presents don't stop!

I was happy to find screenshots from my own Lisas in this collection of Perkins emails. The resolution is pretty terrible, but coincidentally while I've been rummaging through some very old pictures over the holiday, I found the originals on 35mm negatives and photo prints. I don't suppose they'll ever be needed, but it was fun to be reminded of those old photos, in stereo.

Speaking of Applesauce, even though you don't need the hardware to read these disk images, I'll have my hands on my own unit soon. I'm excited about this! I know there have been experiments with using the device to read Twiggy disks. Does anyone know anything more about this?
« Last Edit: December 29, 2022, 10:19:58 pm by stepleton »
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sigma7

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Re: A Wee Cristmas Present
« Reply #17 on: December 30, 2022, 05:55:11 pm »

Speaking of Applesauce, even though you don't need the hardware to read these disk images, I'll have my hands on my own unit soon. I'm excited about this! I know there have been experiments with using the device to read Twiggy disks. Does anyone know anything more about this?
My (unchecked) calculations suggest that a 96 TPI HD drive would be able to position the head over the 62.5 TPI Twiggy disk tracks relatively well.

In the worst misalignment case (Twiggy track 14 where only 45% of the HD head is over the Twiggy track), it looks like the HD head is probably narrow enough to not cover any of the adjacent Twiggy track.

A possible solution is to misalign a second (or more) HD drive so that different tracks are correctly positioned, then interleave the track data from multiple drives.

But perhaps not worthy of a lot of effort due to the lack of Twiggy disks to read.

Attempted spreadsheet attached.
« Last Edit: December 31, 2022, 07:24:43 pm by sigma7 »
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Al Kossow

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Re: A Wee Cristmas Present
« Reply #18 on: December 31, 2022, 04:29:34 pm »

I gave John some twiggy top and bottom samples to play with using the applesauce decoder. You can follow the progress on their discord. I made some disks when I was doing the museum's Lisa 1 restoration using HD media in Twiggy sleeves, then used that in a normal floppy sleeve recently to create the samples. All but the first tracks on the top side were recoverable since the heads are offset on a 96tpi drive. People have been playing with trying to read a Twiggy in a normal drive as a flippy, but no one has actually succeeded AFAIK. You have the problem then that one side has all of the flux transitions backwards. This is also only really useful for data recovery.
« Last Edit: December 31, 2022, 04:31:57 pm by Al Kossow »
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