SomeQuestions about the virtual jtag TCK

I tried to send a 800*480 image throw the vjtag，here is the tcl：

        puts " Begin to read..."
		
		set run_width 0
		set run_height $height
# 		puts 
			
			device_unlock
			
			
			set pix_array(,$run_width) $pixel
			incr run_width
# 			puts "The pixel is $pixel"
			}
			incr run_height -1
			set  run_width 0
			puts "Line.......$run_height"
		}

but the time to send all the data is so long，about 20min，during the process I use the oscilloscope to measure the TCK pin of the usbblaster，it is about 200kHz，the Virtual jtag megafuntion handbook noted：

Note that TCK (a maximum 10-MHz clock, if using an Altera programming cable) provides the clock for the entire SLD infrastructure. 

And the usbblaster ii download cable user guide：The USB-Blaster II download cable has a default TCK frequency of 24 MHz.

I catch the waves throw the signaltaphttps://www.alteraforum.com/forum/attachment.php?attachmentid=12809 ，

the shiftting takes about 96 Ttck when translatting the 24 bits data,even though,the image has 800*480 = 384000 24bit datas, 384000*96 = 36864000,when the tck is 200kHz,it should takes about 36864000/200000 = 184s,about 3min,

I don't know why the transmission is so slow，does anyone can help me?