Hi, I've been actively into Bitcoin for only about a week, although I first read Satoshi's paper about 6 months ago, and found it interesting... I am wishing now that I had dived in earlier.
This is a very "newbie" question, about getting Radeon cards to work in some older, low-budget PC systems...
I picked up an XFX (OEM) Radeon 6770 HD card at Best Buy ($170) to experiment with GPU mining. I tested it on my Dell Precision (Vista Ultimate 32-bit) at work, and it worked fine, and I was able to achieve 180 Mhash/s with guiminer (and a bit more overclocked), which seemed like a reasonable return on investment - estimated payoff time less than a month.
However, now, I am trying this same card on some lower-end PCs that I have at home (a Dell Inspiron running Vista Home and a Compaq Presario running XP), and having rather less luck. Both of these computers have PCI express slots, supposedly, but they lack the extra 75W 6-pin PCI-E power connector that the Dell Precision system had. So, I bought an external supply (430W) which had the appropriate connector, to provide this extra power.
Unfortunately, it is not clear to me that this power configuration is working... On both of these lower-end platforms (unlike the Dell Precision), the ATI driver installers seem to fail to recognize that the board is present. Actually, on the XP system the installer seems to see that some ATI hardware is there, but it still doesn't fully recognize it and install the appropriate software. Also, the external power supply doesn't run its fan at all, unless I try using it to power the motherboard as well, but in that case, the system doesn't even boot (although the fans all start). I haven't tried replacing the entire existing power supply with the new one yet, but I was hoping to avoid that if possible, since I don't want to damage these existing systems.
Since I don't have much experience diagnosing these kinds of problems in jury-rigged power setups, I was wondering if anyone had any other suggestions.
Is it hopeless? Am I just going to have to buy a new chassis/motherboard/etc. in order to use this card? I could keep running it at work, but I don't want to get in trouble...
Thanks for any tips,