Are there any boards with external SRAM/SDRAM available ?

[Berni]

Yes but you have to wait for flash to finish write cycles and you can only erase it in blocks. Also flash usually dies after 100K to 1M writes.

[bsmithyman]

The Winbond W25X40VB serial flash chip that XMOS has suggested as a replacement for the difficult to obtain Atmel AT25 part is blindingly fast with a max. SPI clock of 104 MHz and a dual speed mode giving an effective clock rate of up to 208 MHz!

Yeah, it's faster than the XMOS chips can actually access it, at this point. The only reason I suggested the smaller / slower chips is because they're SRAM (in the case of the Microchip) or FRAM (Ramtron), both of which can survive random access forever (well, 20 years at full duty cycle) and don't have write delays. I've never been that clear on what the write delays on flash chips actually come in at in the real world.

Then there's something like the Numonyx P5Q PCM; 128 Mbit via SPI, 66 MHz speed, but it can do quad I/O at 50 MHZ (which is actually probably faster than the Winbond part, since you could use 4-bit ports to optimize a bit on the XMOS side). No idea about the actual performance or lifetime though.

[ale500]

I wanted some external fast memory to use a frame buffer.

[ale500]

I have a question:

What happens if I put a via instead of a pad where the ball of a BGA ic will sit. That would make a board doable price-wise.

Edit: Forget about it. Even using the "dog-bone" technique and 0.15 mm tracks I do not make it to 0.15 mm separation :(. Well, forget about those 144 pins BGAs.

I think the way will be 2xL1s in tqfp-128.

[leon_heller]

Vias in pads need to be filled, otherwise they wick solder from the pad. Filled vias are expensive, and aren't used very often; none of the usual PCB suppliers offer them. Laser-drilled micro-vias are another possibility, but they are expensive, also.

[ale500]

You are right Leon, I just read about them, and checked the DRC... I'll go with two 128s. Let's see how it plays out.

[PoohEng]

Hi,
Recently I have been looking at the Schmart Boards. They have
a BGA board that may be of use.
I don't have much experience with these so cannot really say much beyond what
they advertise on their site.

[Bianco]

Hi,
Recently I have been looking at the Schmart Boards. They have
a BGA board that may be of use.
I don't have much experience with these so cannot really say much beyond what
they advertise on their site.

For the price of the BGA breakout board, XMOS chip and other components you can buy an XC-1A.

[ale500]

The pitch is wrong. It should be 0.8 mm.

[ale500]

Well the time has come for me to do my own board. As there is nothing available... I 'm designing my own with a L1-128 and a 256kx16 SRAM. It has the following ICs:

XS1-L1-tqfp128
IS61WV51216 (this is the 512kx16 part but I'll use a 256x16, cost reasons).
W25X40BVSS1G (512kx8 FLASH)
TPS3808 (Supervisory)
TPS62260 (1V buck regulator)
2x74LVC573
2x40 FPC connectors for 4.3" 480x272 PSP TFT (one has 3:3:2 RGB and the other one 5:6:5 RGB).
XTAG-2 Connector

The idea with the LCD connectors is that using the 16 bit color version you save a 8 bit port because the data read from SRAM will be latched in the '573. The other option is a bit more traditiona, one 8 bit port is used and no latches are required.

Here is the still-in-progress 80x48 mm two-sided board.

Comments are appreciated

Ale(500)