ugfeldmn@sunybcs.uucp (Jon Feldman) (12/02/87)
[Muncha buncha muncha buncha muncha buncha ST's go with lunch...]
Can anyone tell me the story behind Extra-Half-Brite, and why some
machines have it and some don't? Which Amigas do? Why? How? Where? When?
What? I don't understand! Where's the tea?
Danks,
- Jon
. . . . . . . . . . . . . .
Jon Feldman InterNet: ugfeldmn@joey.cs.buffalo.edu _^--^_
uucp: {decvax,watmath,rutgers,...}!sunybcs!ugfeldmn / . . \
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bending over." --- Frank Zappa ^-----`__U_'
. . . . . . . . . . . . . cegrr@cbmvax.UUCP (George Robbins) (12/03/87)
In article <6924@sunybcs.UUCP> ugfeldmn@joey.UUCP (Jon Feldman) writes: > > Can anyone tell me the story behind Extra-Half-Brite, and why some > machines have it and some don't? Which Amigas do? Why? How? Where? When? > What? I don't understand! Where's the tea? Extra-Half-Brite is a display mode where five bit planes are used to lookup the color for a pixel in the color lookup table, and the sixth bitplane is used to modify the resulting color value by shifting the resulting RGB values right on position. It is kind of a kludge which takes advantage of the fact that the logic for handling six bitplanes was already present to make HAM work, however changing the color lookup table from 32 to 64 entries would have caused an undesirable increase in the size of the Denise chip. Chip cost bears an exponential relationship to area, so you try to avoid major size increases unless better technology is available to compensate. The change was incorporated in Denise Rev 6 which was used in production for about half of the A1000's. However since this half includes almost all the European A1000's, the percentage of US machines with half-brite is somewhat lower than expected. The mode is also present in Rev 8 chips and all A500's and A2000's use either the Rev 6 or Rev 8 chip. There are no functional differences between the two revisions. Commodore didn't make a big fuss about it since it wasn't really a major improvement and there were massive numbers of perfectly usable older chips in the production pipeline. If you don't have one in your machine, you can order a replacement Denise chip for $65.40 list, or whatever deal you can get through your dealer's service department. -- George Robbins - now working for, uucp: {uunet|ihnp4|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@uunet.uu.net Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
peter@sugar.UUCP (Peter da Silva) (12/05/87)
In article <2886@cbmvax.UUCP>, grr@cbmvax.UUCP (George Robbins) writes: > It is kind of a kludge which takes advantage > of the fact that the logic for handling six bitplanes was already present > to make HAM work, however changing the color lookup table from 32 to 64 > entries would have caused an undesirable increase in the size of the > Denise chip. Chip cost bears an exponential relationship to area, so > you try to avoid major size increases unless better technology is available > to compensate. When you do go to a 64-color denise, will it work with the 1000s? Since the 500 and 2000 denise is the same, I'd presume that a 64-color version that would work in them would work in the 1000. Just like some feedback on this... (you *ARE* going to have a 64-color denise, aren't you?) (please?) -- -- Peter da Silva `-_-' ...!hoptoad!academ!uhnix1!sugar!peter -- Disclaimer: These U aren't mere opinions... these are *values*.
ewhac@well.UUCP (12/07/87)
In article <6924@sunybcs.UUCP> ugfeldmn@joey.UUCP (Jon Feldman) writes: > Can anyone tell me the story behind Extra-Half-Brite, and why some >machines have it and some don't? Which Amigas do? Why? How? Where? When? >What? I don't understand! Where's the tea? > This was the story related to me by Dale Luck, and may be riddled with inaccuracy. I make no claims as to truth; it's what I heard. NationalEnquirerMode (ON); In the beginning, there was a chip. This chip could do all the vanilla modes, but HAM mode was buggy. Almost no one saw this version of the chip (except some unlucky dealers whose demo systems had it). Then HAM mode was fixed. And Commodore saw it was good, said it was good, and it was good. And Commodore said, "Go forth and multiply these chips." And there were many chips. Then, an engineer at C-A re-did the chip mask, and discovered that, for next to no silicon space, he could add Extra-Halfbright mode. And he did so, and saw it was good. And Commodore agreed that it was good, and said, "Multiply these chips also." And the engineer said, "Wilt thou use these all-new good nifty chips in thine production system?" And Commodore replied, "Yea, but not until after we've gone through all these old ones first." And so some systems had Halfbright, and some didn't. And the Universal Uncertainty did arise, giving forth many EHB-testing programs. And Commodore did partially resolve the Uncertainty, saying unto the masses, "All 2000's and 500's have the Halfbright feature." The Uncertainty still exists for the 1000, but may be resolved by purchasing on thine own the coveted Halfbright chip, for the draconian price of ~$62.00. NationalEnquirerMode (OFF); Does this help? _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Leo L. Schwab -- The Guy in The Cape ihnp4!ptsfa -\ \_ -_ Recumbent Bikes: dual ---> !{well,unicom}!ewhac O----^o The Only Way To Fly. hplabs / (pronounced "AE-wack") "Work FOR? I don't work FOR anybody! I'm just having fun." -- The Doctor