nVidia driver Fast Writes, what is that?

raska · 10-21-2005, 08:12 PM

while checking out my system (slackware10.2, kernel 2.6.13.2, nVidia driver 76.76), I just found out about this incoherence:

ok everything looks fine here,

Code:

# ls /proc/driver/nvidia/agp
card  host-bridge  status

those files are properly in place, let's look into them,

yeah, that looks like my graphics card:

Code:

# cat /proc/driver/nvidia/agp/card
Fast Writes:     Supported
SBA:             Not Supported
AGP Rates:       4x 2x 1x
Registers:       0x1f000017:0x1f000104

it doesn't support SBA, what's that anyway?

lspci -v output about the graphics card:

Code:

01:00.0 VGA compatible controller: nVidia Corporation NV17 [GeForce4 420 Go 32M] (rev a3) (prog-if 00 [VGA])
        Subsystem: Hewlett-Packard Company: Unknown device 006d
        Flags: bus master, 66Mhz, medium devsel, latency 248, IRQ 21
        Memory at ea000000 (32-bit, non-prefetchable) [size=16M]
        Memory at f8000000 (32-bit, prefetchable) [size=64M]
        Memory at fc000000 (32-bit, prefetchable) [size=512K]
        Expansion ROM at fc080000 [disabled] [size=128K]
        Capabilities: [60] Power Management version 2
        Capabilities: [44] AGP version 2.0

medium devsel, huh? I don't like that.

here's where the card is hosted, as the graphics card it also supports Fast Writes:

Code:

# cat /proc/driver/nvidia/agp/host-bridge
Host Bridge:     nVidia Corporation nForce3 Host Bridge
Fast Writes:     Supported
SBA:             Supported
AGP Rates:       4x 2x 1x
Registers:       0x1f000217:0x00000104

this actually supports SBA. Weird, isn't it?

this is the lspci -v info about it:

Code:

00:00.0 Host bridge: nVidia Corporation nForce3 Host Bridge (rev a4)
        Flags: bus master, 66Mhz, fast devsel, latency 0
        Memory at f0000000 (32-bit, prefetchable) [size=128M]
        Capabilities: [44] #08 [0180]
        Capabilities: [c0] AGP version 2.0

fast devsel, huh? how come?

now, let's peek out how the driver is being used:

Code:

# cat /proc/driver/nvidia/agp/status
Status:          Enabled
Driver:          AGPGART
AGP Rate:        4x
Fast Writes:     Disabled
SBA:             Disabled

why the Fast Writes thing is not enabled?
what does it do?
how can I enable it?
once enabled, shall it run the games noticeable faster?
what is about the SBA feature?

freakyg · 10-21-2005, 08:27 PM

look what I found.........he he

http://www.dslreports.com/faq/5588

SBA==side band addressing
<edit/>read this also...........

http://www.cs.unc.edu/~sud/tips/nvid...#card_tweaking

raska · 10-22-2005, 11:55 AM

cool! thanks, I shall check this out tonight at home

thanks again