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PostPosted: Thu Dec 01, 2005 2:08 am 
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Joined: Tue Dec 21, 2004 8:35 pm
Posts: 600
Location: Argentina
I have unclear how the ppu does to render at low level the AT bytes. Im little confused, 2C02 ref says that (correct me if im wrong):

- Every 8 pixel obtanains the AT byte
- The pallete select data is selected through a 2-bit 1-of-4 selector (can somebody explain me this?)
- Then the Data (taked from the selector?) feed 2 - 8 bit shift registers that i dont know if they shift left or right.
- The 4 bit pixel data is taken from the 2 16 bit shift registers (PT) and from 2 - 8 bit registers (AT).
- Finally the 4 bit value goes to the multiplexer.

I could get to work pt behavor (low 2 bits of pixel), but AT i get stuck. :cry:

Thanks in advance.

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PostPosted: Thu Dec 01, 2005 10:08 am 
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I would speculate it goes something like this:

Code:
+-----------------+
| Fetched At Byte |
+-----------------+
  * * * * * * * *
  | / | / | / | /
  |/  |/  |/  |/
  ||  ||  ||  ||
  **--**++**--**  <-- 2-bit 1-of-4 selector picks only 1
        ||
        ||  -------
        || /-------  2 input bits from pattern data (CHR)
        ||//
        ||||
        ||||
  +--------------+
  |      Out     |
  +--------------+


Though I don't know why a low level understanding would be necessary. Are you having Attribute lookup problems or something?


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PostPosted: Thu Dec 08, 2005 12:39 am 
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Location: Argentina
Quote:
Are you having Attribute lookup problems or something?


no, with my old engine, but yes with my new one.
Anyway installing linux and playing with partitions made me lost my new, and the most recent buckup i had stored the old one.
so, i have to do it again. :(
But thanks for the help.

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PostPosted: Thu Dec 08, 2005 2:37 am 
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Joined: Mon Sep 27, 2004 8:33 am
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Location: Central Texas, USA
Has the cost of floppy disks/CD-Rs/hard drives/online disk storage gone way up recently? I regularly read about people losing source code, but I doubt anyone here writes enough source code in a year to fill up even one package of 1.44MB floppy disks.


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PostPosted: Thu Dec 08, 2005 3:20 pm 
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Location: NE Indiana, USA (NTSC)
blargg wrote:
Has the cost of floppy disks/CD-Rs/hard drives/online disk storage gone way up recently?

No, but the price of secure real estate to store them may have. Do you store your offsite backups in a bank's safe deposit box or a comparably secure location?


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PostPosted: Sat Dec 10, 2005 3:14 pm 
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Quote:
Do you store your offsite backups in a bank's safe deposit box or a comparably secure location?


Onsite backups protect data from hardware failures, viruses, user error. Offite backups protect from fire and theft. Safe-deposit-box offsite backups protect from malicious parties. Personally, fire is the most I am willing to protect my data from (a copy or two at parents/grandparents house is sufficient). If someone's determined to destroy my data, there's not much I can do.


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