[Dri-devel] Re: R200 and 100Mhz system memory

[Smitty <sm...@wa...>]

 
> Message: 3
> Date: Sat, 17 Aug 2002 11:45:03 +0200
> From: Stephane Chauveau <s.c...@ch...>
> To:  dri...@li...
> Subject: [Dri-devel] R200 and 100Mhz system memory
> 
> Hi,
> 
> Yesterday, I noticed that my bios was configured to use
> 100Mhz memory. I did not know exactly what kind of memory
> I was using but I decided to change the configuration to 133Mhz.
> Guess what! It works fine so I probably have 133Mhz memory.
> 
> I believe that my system is more responsive  but the most
> impressive was the effect on my Radeon 8500LE.
> I was able to play RTCW more than 3 hours without a single
> crash. Before that, my uptime in RTCW was usually not more
> more than 5 minutes.
> 
> What do you think of that?
> 
> Could it be that Radeon 8500 have problems with 100Mhz
> memory?
> 
> PS: my system is an Athlon 900Mhz, VIA motherboard, 128Mb
> of 133Mhz memory ;-), XFree 4.2 + r200 bleeding edge driver.
Hmn a VIA motherboard I dont have one of those, could you be a bit
more specific. <g>
 
One thing that springs to mind is that it is possible to run thos old
boards at 100MHz FSB with the memory at 133MHz (3:4) ie asynchronous, this
increases latencies (bad for performance good for stability) but increases
bandwidth (good for performance).

Based on the assumption that this is what you are doing I'd say the increased
latencies require less strict timings (it is in effect waiting more) and this
has improved your stability.  
 
> From: Steven Walter <srw...@ya...>

> It's possible that you have 133MHz memory that is not backwards
> compatible to 100MHz.  By running it at such a frequency, it was more
> unstable and prone to errors, which would easily crash a memory
> intensive game like RtCW.  (Yeah, I'm not really sure how down-clocking
> something can make it unstable, either.  My theory is that lazy
> manufacturers don't fill in the SPD information for any speed other than
> the frequency it was designed for, so BIOSen have to make crazy guesses
> about it)
Very interesting I was not aware that it could be backward incompatible.

Higher specced memory has better trace design / chips and can handle lower 
latencies.

Got any links on this?

Liam
----
it depends