# Radeon card observations and questions **URL:** \ **Category:** Uncategorized\ **Created:** [January 31, 2002, 2:43am UTC](https://psychtoolbox.discourse.group/t/radeon-card-observations-and-questions/1295 "2002-01-31T02:43:35Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [January 31, 2002, 2:43am UTC](https://psychtoolbox.discourse.group/t/radeon-card-observations-and-questions/1295/1 "2002-01-31T02:43:35Z")
Hi Ben, I have starting playing with a Radeon card. Thanks for your work on this. a) I integrated your SetClut etc. stuff into the master version of the toolbox so it will be distributed with the next release. The card I have is in a new G4 Tower and was the result of asking Apple to put a Radeon card in the PCI slot. The driver has a number between the two you check for in your code, so I added it to the list. Preliminary checks indicate that the driver indeed supports 10-bit stuff with whatever version of the Radeon Apple put into my machine. I haven't yet actually measured light output with a single step in the least significant bit to verify that it really is 10-bits, but I will. Certainly the software behaves as if it is correctly accepting the 10-bit input, but I don't think I could visually distinguish the output of true 10-bit DACs from 8-bit DACs coded to work with a 10-bit interface. I did once verify that the Radius cards really do have 10-bit DACs. b) My timing of the SetGamma and SetClut calls shows them to be very slow. Indeed, the call takes very close to a whole frame time. Most of the time it finishes before the next vertical retrace, but sometimes not. Indeed, it is almost as if it waits for blanking both at the beginning and end of the call but that sometimes my loop makes it back to the top before the end of the blanking period. I'm not confident of this diagnosis and haven't yet played with any of the optional preferences in SCREEN, nor yet run ScreenTest to see what it thinks. (I had to go about 10 minutes after my initial observations.) Do you have any insights or data on this point. c) I have some more G4's coming and Apple no longer will build the Radeon PCI cards in (as of this past Monday). ATI seems to sell a 7500 and an 8500. Do you know what the difference is, and whether either or both is supported by the 10-bit drivers? d) I wrote a routine that will take cluts in the range 0-1023 and depending on the hardware convert them to the right form to pass to SetClut. For Radius 10-bit, this means leaving it alone, for Radeon this means shifting 6 bits towards the high end, and for 8-bit hardware it means shifting the two least significant bits out. This routine eases coding hardware independent code. I'm not sure it's the exact right solution. Once I understand a little more I'll send you what I've got. Best, David ---
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [January 31, 2002, 11:49pm UTC](https://psychtoolbox.discourse.group/t/radeon-card-observations-and-questions/1295/2 "2002-01-31T23:49:27Z")
--- In psychtoolbox@y..., David Brainard \ wrote: > \> > \> Hi Ben, > \> > \> I have starting playing with a Radeon card. Thanks for your work on this. [snip] > \> I haven't yet actually measured light output with a > \> single step in the > \> least significant bit to verify that it really is 10-bits, but I > \> will. Certainly > \> the software behaves as if it is correctly accepting the 10-bit input, but I > \> don't think I could visually distinguish the output of true 10-bit DACs from > \> 8-bit DACs coded to work with a 10-bit interface. Hi Ben, David, all, I've been setting up a 10-bit Radeon, too (thanks Ben!), and just finished some informal measurements (just using a Tektronix photometer). Single steps appeared to yield detectable changes in intensity, so good news. I just sampled a bunch of random values (extremes and near center), nothing all that systematic, but at a first pass all was well. -Alex Alex Huk Senior Research Fellow Dept. of Physiology & Biophysics University of Washington web: www.shadlen.org/huk