Architecture Overview
3-8
GMS30C7201 Data Sheet
3.5
Performance
ARM720T operation
The actual performance of the device will be highly application specific as well as
dependent on the speed of memory attached and the rate at which data is being
transferred to the DMA peripherals, in particular the LCD and VGA.
If a particular application or part of application is executing entirely from within the 720T
cache then the memory speed and peripheral DMA bandwidth may not have any affect
at all. However most applications will require access to either the static memory
interface or the SDRAM interface for its data structures and for instructions whenever
there are cache misses. The cache miss rate will have a large impact on the achievable
performance, however it is impossible to predict this for any general application.
It is possible though to give some indication of the potential performance of the device
when operating out of cache.
Run Mode operation (Cache on and operating at 60MHz, ASB clock at 30MHz):
Approximately 75K Dhrystones/s (~42.6 DMIPS)
Slow Mode operation (Cache on and operating at the ASB clock frequency of 30MHz):
Approximately 44K Dhrystones/s (~25 DMIPS)
* Both sets of figures assume two wait state memory external memory is available and
no peripheral DMA is active.
SP7 (Piccolo) operation
Once again it is not possible to generalize about the performance achievable on
ARM720T when the SP7 co-processor (Piccolo) is being used, it will depend entirely
on the frequency with which the ARM720T must transfer data to or from the SP7 co-
processor which in turn is entirely application dependent.
The performance of the ARM7TDSP processing element is best illustrated by its
performance for particular applications - it not possible to specify its performance in
generalized MIPS terms.
SoftModem Performance
The following performance benchmarks have two columns. The first indicates the peak
processor requirement when averaged over two frames (triple frame buffering is used
to ensure no processor time overflow occurs). The peak occurs during the modem
startup (training) sequence. The average value represents the softmodem requirement
once the startup sequence has finished. All figures represent a system with data held
in SDRAM, code held in 2 wait state burst ROM, and 620x240 monochrome 4bpp LCD
being displayed. The table below assumes the CPU clock is running at 60MHz and the
memory clock at 30MHz.
Modem standard
peak/MHz
average/MHz
V34bis with V42bis
54
42
v32bis
29
21
V17fax
14
14
Table 3-1: CPU clock cycles used for SoftModem