Evan Langlois wrote:
On Sat, 2005-07-16 at 08:51 +0100, jan.thomas@bt.com wrote:But even now I'm used to a 2x1.8GHz G5, my TT still doesn't feel sluggish or obsolete at all. As long as I don't use it to browse the web. ;o)Yeah, odd that. My TT is crisp at only 32mhz, but my 80/25mhz CT60'd Falcon is painfully slow screen-wise.Sound to me like bus contension. Doesn't the TT have a 32Mhz bus? I know its a 32 bit wide bus, and the Falcon is 16 bit wide, so right away there is half the bus gone. So, 25Mhz * 16 bit = 50MB/s. 32Mhz * 32 bit = 128MB/s. Considering that screen draws are memory intensive by
Actually, I seem to recall the TT's RAM bus being 64 bit wide for the video system and the Falcon's 32 bit (the CPU's both having half that), but I may be wrong there.
But, the CPU's have far worse bandwidth to video RAM than you might think.A 100 MHz CT60 with a 25 MHz Falcon bus gets something like 6 Mbyte/s for the CPU when reading from ST RAM and 10 MByte/s when writing (numbers from files in the KRONOS distribution). My AB040 Falcon gets even less, at something like 4/6 Mbyte/s, IIRC.
The TT should be a lot better, though. It also can't deal with as high resolutions and bit depths as the Falcon, so the contention from the video system is lessened further.
It's funny, though, that if that measly sub-10 Mbyte/s bandwidth is used to communicate with a reasonable graphics card, even the Falcon will feel really speedy. (Granted, you don't want to go blitting large amounts of data between normal RAM and the card, but that can usually be avoided.)
I'm running about 1600x1200, 32 bit, 70hz .. 525MB/s. Luckily the ATI can do that - pretty sure the card uses dual-ported VRAM or something.
Dual ported RAM hasn't been used in main stream graphics card for a very long time. It costs too much and there's really no reason for it with today's bandwidths. Top end modern graphics cards are up somewhere in the 30-60 Gbyte/s range now.
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