Amiga.org
Amiga computer related discussion => General chat about Amiga topics => Topic started by: HellCoder on October 24, 2008, 11:30:18 AM
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Hi,
Anyone out there having a Blog related to the Amiga? I just found this blog. All graphics in this blog are drawn with Imagine. The blog itself is about a game I'm currently working on. (This blog is my blog, spoken trough an avatar) The game itself will reveal itself in time at the blogsite. :)
http://redmond.elasticore.nl
have fun.
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I have my blog here (http://www.iboughtavoodoolaptop.com) it is a split between Amiga and Voodoo PC. It started out as a watchdog blog for Voodoo, but it is morphing more into Amiga. I don't ever claim to be an expert on anything, and corrections and additions are always welcome, but I sure get a lot of Amiga questions.
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Hmmm - interesting playground!
I had an Amiga-related blog on my old website (www.conceitedjerk.com), which sadly is no longer around. It was mostly about using my A2000 (and to a lesser extent my A4000) in my everyday routine. I'm thinking of adding an Amiga section to my current blog (http://conceitedjerk.blogspot.com) though - possibly even recording a podcast once I fix/replace my Toccata card! :-)
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Like if anyone care, I have shut down the old blog and moved it to the Amiga Lounge (http://www.amigalounge.com)
I am working right now on a full website, so stop on by, and please fell free to make comments, corrections, and other input.
I just have s fast history of hardware up there now, nothing to in depth, and mostly "borrowed" from Wikkopedia.
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I have a blog or two about Amiga, the one in the sig is the one most updated.
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Dunno if I count.
http://www.techtravels.org/amiga/amigablog
Amiga floppy project blog
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See the link in my signature below. :-)
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Here is my blog that hits on Amiga topics quite a bit.
http://somethintodu.blogspot.com/
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I also added a blog onto my side now.
http://www.amigaworld.de
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>by kamiga on 2009/1/13 23:37:57
>Dunno if I count.
>http://www.techtravels.org/amiga/amigablog
>Amiga floppy project blog
>So the normal floppy sync pattern is 0xAAAA 0xAAAA 0×4489 0×4489, but why do we see 0×2AAA ??
>So, 0×2AAA is 0010 1010 1010 1010. right? We’re missing the first bit. It turns out there was a bug in the MFM encoding routine. It was fixed March 16th 1990 at 1:08am in the morning, in revision 32.5 of the trackdisk.device.
It's suppose to be missing the first bit according to my tests with floppy simulation. Supposedly, it allows the heads to sync up properly to beginning of track. Since you have the hardware to analyze these patterns, can you figure out what pattern it reads for high density disk and what speed? Parallel port just not fast enough my machine to analyze the high density disks currently.
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amigaksi wrote:
It's suppose to be missing the first bit according to my tests with floppy simulation.
The unencoded SYNC word string is 0x0000A1A1, which encodes to 0xAAAA (put clock pulses before data pulse, so 0000 becomes 10101010. Then encode A1A1, which would normally encode to 0x44A9 0x44A9. But the "FUNNY A1" encoding, as the Commodore engineers called it, didn't use the normal method of encoding for the sync word --- so the driver/software/whatever could tell the difference between the SYNC and real data. They instead opted to encode A1 as 0x4489 (44 is normal as is the 9), so the "missing clock pulse" referred to in the documentation is the 11th bit(counting L to R, MSB to LSB) which would normally be a "1" be changed to a "0" instead. Note that it also doesn't break any MFM encoding rules as far as too-long-run-of-0's-or-1's.
This, my friend, is the bit you are referring to. (not the first missing by mistake-in-some-versions-of-OS bit) :)
Normal MFM encoding of 0x0000A1A1 = 0xAAAA 0xAAAA 0x44A9 0x44A9
Special SYNC MFM encoding of 0x0000A1A1 = 0xAAAA 0xAAAA 0x4489 0x4489
Besides, the AAAA AAAA is considered to be a preamble, and you want something nice and consistent -- easy to PLL lock to for recovering the data. Most of the OS uses a 16-bit SYNC word of "0x4489" because this is the important stream of bits to ensure you are properly locked.
(the code in my floppy controller uses 4489, as well)
Hope this helps
P.S. you should probably respond to my blog posts on my blog versus on another website
P.P.S. Hopefully this is clear, it's 20 minutes to 2am.