Calculating the Potential of that GeForce3
tnaw_xtennis 2001.03.13

The 3D rendering capacity i.e. fill rate of today graphic processor is never seen actualized due to the acute video memory bandwidth or CPU limitation encountered. By applying calculations concerning memory-bandwidth and fill rate, this page will disclose how GeForce3 is doing with its fill rate of 1000 mega pixels per second, how fast it will be without memory bandwidth or CPU limitation, and what the performance is when its video memory is overclocked.

Table 1 shows the performances GeForce3 give us running under non-antialiasing and antialiasing modes. The values in the table are obtained by summing up those reported benchmarking results according to the fact, confirmed by Table 2 and Table 1 in Ref. 1, that 3D graphics performance of a system is determined by that video card on high screen resolution.

The formulas applied for the calculating are listed below. Refer to the "Calculating the Potentiality of Your GeForce2" for detail description.

3D_rendering_memory_bandwidth = resolution * frame_rate * C

Fill_rate = resolution * frame_rate * depth_complexity

The calculating results in Table 3 shows that (1) At 1600x1200x32bit, the condition that 3D performance is limited by video memory bandwidth, only 69% fill rate of GeForce3 video processor brings into play. Without the memory bandwidth limitation, a GeForce3 will have a 104 fps performance. (2) At 800x600x32bit, the condition that 3D performance is limited by CPU, only 45% fill rate of GeForce3 video processor brings into play. Without the CPU limitation, a GeForce3 will have a 308 fps performance.

The video memory speed of GeForce3 product is set to 230MHz, since 3.8ns RAM is applied, we could overclock the video memory to a speed of 263MHz with easy. Table 5 shows the calculating performances of the overclocked GeForce3. At 1600x1200x32bit, a GeForce3 has 72 fps performance, while the GeForce3 with video memory overclocked will have as high as 80% of fill rate brings into play and hence has 83fps performance.

Table 1. Quake3 (32bit color depth) performance (fps) of GeForce3*

Quake3 Performance	1024x768	1280x1024	1600x1200
GeForce3 No AA*	/	102	72
GeForce3 2x AA**	85	50	32
GeForce3 Quincunx AA**	71	42	27
GeForce3 4x AA**	51	28	/

* values from Table 2
** values from  Table 1 in Ref. 1

Table 2. Quake3 (32bit color depth) performance (fps) of "GeForce3 (Driver 10.8) / GeForce2 Ultra"

Table 3. Testing and Calculating Quake3 Performances of GeForce3 and GeForce2 Ultra

Table 4. Quake3 Performance of GeForce3 and GeForce3 with video memory overclocked to 263MHz

1600 x 1200 x 32bit	GeForce3	GeForce3 with overclocked video memory
Quake3 Frame_rate obtained by testing (fps)	72	83
Video Card Memory Bandwidth (GB/s)	7.360 (230MHz)	8.416 (263MHz)
Video Processor Fill Rate (Mega Pixels/s)	800	800
Video_refresh_memory_bandwidth (GB/s)	0.576	0.576
3D_rendering_memory_bandwidth of the video card (GB/s)	6.784	7.84
C	49.1	49.1
Fill_rate corresponding to the Quake3 Frame_rate obtained by testing (MB/s)	553	637
Fill Rate of the video card that brings into play (%)	69%	80%
Video core speed corresponding to the Quake3 Frame_rate obtained by testing	138 MHz	160 MHz
theory un-memory_bandwidth-limited Quake3 Frame_rate (fps)	104	104
theory memory_bandwidth needed (GB/s)	10.396	10.396

* Pentium 4 1.5GHz, Screen_refresh_rate = 75Hz
** depth_complexity = 4

Table 5. Quake3 (32bit color depth) performance (fps) of GeForce3 with memory overclocked to 263MHz

Quake3 Performance	1024x768	1280x1024	1600x1200
GeForce3 No AA*	/	118	83
GeForce3 2x AA**	98	58	37
GeForce3 Quincunx AA**	82	48	31
GeForce3 4x AA**	59	32	/

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