heh when I compared my old ASUS X800 XT Platinum Edition with my new Sapphire X1900 XTX it kinda doubed the idea when I compared the 9700 Pro with the X800 XT PE

the 9700 Pro was the predecessor of the famous 9800 Pro so I skipped the 9800 seres and waited till the X800XT PE AGP was ready for launch.
here the Hercules 9700 Pro compared to the massive X1900 XTX gosh these 2 compared in performance was rather like turing the world of PC graphics inside out

ATi R300 Hercules 3D PROPHET 9700 Pro AGP 128MB DDR Limited Red Edition Rev.C 0243 [normal Herc's had blue PCB's]

ATi R420 ASUS AX800 XT Platinum Edition AGP 256MB GDDR3 Rev.A 0436:

ATi R580 Sapphire ATi Radeon X1900 XTX PCI-E 512MB GDDR3 Rev.A 0552

The R580 chip is a great piece of technology it runs Quake4 & HalfLife2 EP1 @ 1600 x 1200 x32 Ultra settings with FSAA x6 AF x16 without probs on Athlon64 X2 4400+ Toledo setup on the Philips Brilliance 109SP 19" CRT monitor.
This was pretty difficult for the X800 XT PE though, had to turn off FSAA and AF to get a nice fluid gameplay of around the 57 fps that was done on the Dual OpteronDP 244 + 1GB PC3200ECC Reg LL a few mounths ago but then using the same reso also on the Philips Brilliance 109SP 19" CRT monitor.
The X1900 XTX does about 3 times of that

okay on the X2 4400+ + 2GB PC3200 ofcourse it a much faster SMP setup at first, at second twice the amount of ram and at third faster chipset no ECC Reg. and new tech overall.
The X1900 XTX has 48 pixelshader Processors and 8 Vertex shader units while the X800 XT PE only had 16 pixelshader Processors and 6 Vertex shader units and a 256 Bit Memory controller while the X1900XTX has a nice 512Bit Ringbus Memory controller which also does a great job of do'n the crunching stuff.
to be honest the ATi R4.xx VPU's was a great improvement over the R3.cc VPU's only they lacked Shader Model3.0 which I did expect to be in them, but they had a great advantage when FSAA and AF was combined in the most Direct3D titles the R4.xx cards took the lead thier performance in OpenGL apps was alittle dissapointing the GeForce 6 series just were best at do'n that games like Doom3, Quake4 which was just around the corner and other OpenGL based stuff, but games like HalfLife2 rocked on the ATi cards that was Direct3D at it's best allrighty

that R420 aka X800XT PE AGP gave me many hours of fun gameplay at it's time of day, the Laptop has an ATi R420 8 pixelshader processors/4 vertexshader units 256Bit GDDR2, but it still does show me what the R4.xx was capable of, just toobad that the R4.xx series had no ShaderModel3.0, maybe it wasn't possible ofr one or other reason, dunno about that.
R420 = MR9800 - X800Pro/XT/XT PE AGP cards
R423 = MRX800/Pro/XT - X800Pro/XT/XT PE AGP cards PCI-E
Why the $23 PCI based is and the R420 AGP is that the AGP varriant was made first and was mounted with the AGP to PCI-E Railito bridge chip and also AGP PCI-E wasn't the main VGA type of it's time, though that did change when 480 came out aka X850 series.
R480 = X850Pro/XT/XT PE PCI-E cards
R481 = X800Pro/XT/XT PE AGP cards
Why R481 is AGP is because that the R480 the PCI-E version was made earlier the R481 had the Railito AGP to PCI-E bridge chip whch made the R481 an AGP varriant of the R480