Thank you for contacting us. We looked at the product attributes of both chips you mention and as you pointed out, the main difference is the memory size. The document that lists the considerations you should take while designing with the Quark X1000 is the PDG, which can be found here: http://www.intel.com/content/www/us/en/embedded/products/quark/quark-x1000-platform-design-guide.html
The SPI Flash Design Guidelines can be found in Section 11.
In the description you can see that: “Each SPI flash device can be up to 64 Mbytes (512 MBits)”. These 64 Mbytes is the memory size of the W25Q64FVSSIG. I believe the upgrade you want to perform won’t be possible, because the memory size of the flash you want to use exceeds the value listed in the PDG. Please take a look the section mentioned, for the guidelines on how to choose a memory that works with your Quark X1000.
At the end of section 11 you can see a list of serial flash vendors in case you want to consider additional devices.
Let us know if this answers your question.
I reviewed the datasheet of both the W25Q64FVSSIG and the W25Q128FVSIG-ND and you’re right, the W25Q64FVSSIG is 64MBIT and the W25Q128FVSIG-ND is 128MBIT, not Mbyte. I apologize for the confusion. In that case, it seems that the W25Q128FVSIG-ND meets the guidelines established in the PDG. I apologize once again for the confusion and let us know if there’s anything else we can assist you with.
We don't see W25Q128FVSIG-ND part in quark software source files.
BIOS code of Quark supports only below parts.
Supported SPI Flash Devices:
SpiFlash25L3205D // Macronix 32Mbit part
SpiFlashW25Q32 // Winbond 32Mbit part
SpiFlashW25X32 // Winbond 32Mbit part
SpiFlashAT25DF321 // Atmel 32Mbit part
SpiFlashQH25F320 // Intel 32Mbit part
SpiFlash25VF064C // SST 64Mbit part
SpiFlashM25PX64 // NUMONYX 64Mbit part
SpiFlashAT25DF641 // Atmel 64Mbit part
SpiFlashS25FL064K // Spansion 64Mbit part
SpiFlash25L6405D // Macronix 64Mbit part
SpiFlashW25Q64 // Winbond 64Mbit part
SpiFlashW25X64 // Winbond 64Mbit part
SpiFlashQH25F640 // Intel 64Mbit part
Could you please check and let us know how to use W25Q128FVSIG-ND for our project?