#64 VT3108: HT delays are problematic for scan-out.

closed-fixed
Luc Verhaegen
None
9
2006-07-07
2006-07-06
Luc Verhaegen
No

UMA designs rely on main system ram. Formerly, and on
all other designs, this system ram sits off the
northbridge; the ram controller is on the same slab of
silicon as the unichrome. On all recent AMD desktop
CPUs, the ram controller sits off the CPU.

Apart from obvious bandwidth and latency problems when
doing graphics intensive stuff, there is also another
problem.

On my Mitac 8889 laptop, a usb device needs to be
plugged in for the display to be stable. Otherwise the
start of the scan-out buffer (after VSync) will be missed.

The same is visible when using the Video3 overlay
engine full screen. Here the effect is slightly
different, but the cause is likely to be the same.

Need to dig out Athlon64 datasheets to see wether this
can be correct or improved.

Discussion

  • Luc Verhaegen
    Luc Verhaegen
    2006-07-07

    • status: open --> closed-fixed