BIOS -> UC oder USWC

[ALeh]

Hat irgendjemand hier im Forum schon mal Unterschiede zwischen den BIOS-Einstellungen UC bzw. USWC (Video Memory Cache Mode) festgestellt. Laut meinem Mainboardhandbuch soll die Änderung dieser Einstellung ja brachiale Leistungsschübe hervorrufen. Ich frage mich bloß wobei ? Weder Benchmarks noch sonstige Messungen lassen irgendeinen Unterschied am System erkennen.

[BadFred]

Asus Board? ;)

Bei USWC (uncached speculative write-combining) werden Zugriffe zu einem längeren Burstzugriff "gebündelt".
Leistungsvorteile sind marginal, jedoch ist die Option einflussreich in Bezug auf die Stabilität.
In meinem Board z.B. sind Radeon9700(Pro) *nur* mit USWC stabil zu betreiben.

[ALeh]

Originally posted by BadFred
Asus Board? ;)
In meinem Board z.B. sind Radeon9700(Pro) *nur* mit USWC stabil zu betreiben.


Jawoll... Asus P4PE

Wie macht sich denn bei Dir die "Unstabilität" bemerkbar wenn Du auf UC schaltest ?

[BadFred]

Da ich eine ganz tolle GF2MX habe (=:asshole: ...), habe ich *das* Problem nicht ... :-/

Es gibt da aber ein paar Worte drüber, nämlich hier:

http://www.hardocp.com/article.html?art=Mzk4



Zitat: "The next photo shows Video Memory Cache Mode, which is a volatile setting. Enabling USWC can cause the machine to lose video with video cards that do not support it. According to the literature, USWC is an acronym for "Uncacheable, Speculative Write Combining", and means "will make video go faster if your card supports it". What the technology actually entails is not discussed in the literature, but as it makes its way into the mainstream, I'm sure we will learn more about it.

[H]'er Richard Sanders had this to add: Enabling USWC allows several small writes to be buffered up and sent to AGP as one write. Since graphics data tends to have very strong locality, this increases the throughput of the bus and unloads the processor to some extent. But it also increases the latency of the small writes and can cause slowdowns when the writes are more random... as always it's a tradeoff that must be made based on benchmarking your typical workloads.

This extra latency that you get when enabling USWC can work for you on a high OC by allowing the AGP card more time between writes. It's possible that by performing the writes immediately in UC mode, wait times between writes were too short because the bus was clocked so far out of spec. Same principle as increasing the memory timings for high OCs."