April 24, 2025
STM32F746 Discovery Kit - Introduction
The board can be powered from the USB cable to the ST-Link connector.
What this gives us
- STM32F746NGH6U
- 1 Mbyte flash (on chip)
- 340 Kbytes ram (on chip)
- BGA 216 package
- 25 Mhz crystal nearby
- STM32F103CBT6 for ST-Link
- SMSC USB3320C ULPI Phy for HS USB
- 4.3 inch RGB 480x272 color LCD-TFT w/ touch screen
- ISSI IS42S32400F 128 Mbit DRAM (4Mx32), i.e. 16 Mbyte
- 128 Mbit Quad-SPI flash chip (16 Mbyte)
It is interesting to compare this to the STM32F429 I also have on a discovery board.
The F429 has 2M of flash and 256 Kbytes of ram on the chip.
Note that specific F429 chips can have 512K, 1M, and 2M of flash, but
2M seems most common and what is on the discovery board I have.
The big advantage of the F746 is the M7 core that runs significantly
faster at the same clock rate (see below).
The description of the discovery kit says that only half (64 Mbit -- 8 Mbytes)
of the DRAM is accessible.
Note the USB Phy Chip
I have other boards with HS capable USB controllers that require an
outboard HS Phy (but don't have one) and must be run in FS.
This board has an outboard HS Phy, so this can run at 480 Mbit.
Cortex M4 versus M7
I read that the M7 offers twice the performance of the M4, presumably at the same clock rate.
The M7 has a 6 stage superscalar pipeline with branch prediction.
The M7 also has double precision floating point.
The M7 has optional I and D caches.
Needing to manage caches adds quite a bit of complexity.
In particular working with the D cache and DMA requires careful attention.
I see someone estimating that the M7 would "feel" 1.65 times as fast as an M4 at the same clock.
Feedback? Questions?
Drop me a line!
Tom's Computer Info / tom@mmto.org