How fast is Teensy 4.1 PSRAM?

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Quick question-

Just how fast is the PSRAM on a Teensy 4.1? Basically, I'm trying to figure out if it would be fast enough to store a framebuffer for VGA or not.

Thanks!
 
There are TFT displays in use - see forum - where a DMA frame buffer is used for display update. Higher res where the 512KB of RAM2/DMAMEM isn't big enough.

It is SPI - posts like this : Support-for-the-ILI9488-on-T3-x-and-beyond

If the same for VGA transfer rate and size ... that may be out there too ... though not sure if the VGA seen had that feature ...
 
The answer really depends on some details, especially the number of bits or bytes per pixel.

The chip at 88 MHz clock has a bandwidth of about 40 MByte/sec, or about 60 MByte/sec if you increase to the maximum clock speed.

For VGA, 640 x 480 x 60 Hz = 18.4 Mpixel/sec. So if you store only 8 bits per pixel, it's probably fast enough. If you store 32 bits per pixel, definite not enough.

But bus latency could also be a serious problem. You'll probably need something like FlexIO to serve as a FIFO for the outgoing data. Might be possible to get it working, but could be quite a challenge.
 
The answer really depends on some details, especially the number of bits or bytes per pixel.

The chip at 88 MHz clock has a bandwidth of about 40 MByte/sec, or about 60 MByte/sec if you increase to the maximum clock speed.

For VGA, 640 x 480 x 60 Hz = 18.4 Mpixel/sec. So if you store only 8 bits per pixel, it's probably fast enough. If you store 32 bits per pixel, definite not enough.

But bus latency could also be a serious problem. You'll probably need something like FlexIO to serve as a FIFO for the outgoing data. Might be possible to get it working, but could be quite a challenge.

Yeah, would definitely be only 8 bits per pixel... Also thinking about going for 640x400 instead of 480. If I do that, then there should be enough regular RAM on the Teensy 4 to make it work.

I'll look into FlexIO.

Thanks!
 
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