2013年2月4日 · The most recent incarnation of PCI RAM cards was produced by Gigabyte in 2005 and 2006 under the names i-RAM and GC-RAMDISK, respectively. They supported 4 slots totaling 4 GiB of DDR-400. The transfer rate was that of …

2019年12月9日 · Last hardware board for consumers I found was Gigabyte GC-RAMDISK i-RAM circa 2006. These fell out of favor as they require battery backup like array cache modules, and as non-volatile solid state got faster. Yes, reading a MB from DRAM is about 4 microseconds, faster than 62 us or so from SSD. For in the best case a 15x speed up, are you ...

2020年12月10日 · This appears in lspci on my Dell XPS 13 9310: 0000:00:14.2 RAM memory: Intel Corporation Device a0ef (rev 20) Does RAM work over PCIe now?

2021年12月5日 · The M.2 slot only supports up to x4 PCI-E lanes, which, with the PCI-E 4.0 standard, limits the bandwidth to ~7.9 GB/s and the far future PCI-E 5.0 standard to a likely 15.8 GB/s. As for virtual memory, yes, similar to a HDD, we can use an SSD for virtual memory, but keep in mind this is as an extension to RAM, not a replacement.

2012年10月22日 · Your interpretation of the BAR setup is correct. Then how does it differ. The device's on board memory/registers usually is a special RAM, it may be bi-port RAM (when each cell has two ports one is connected to the host bus, another to the device's internal bus, this allows faster and concurrent access from both sides), it may be a registers or even directly some inputs or outputs of some FPGA ...

2015年10月18日 · That is, one PCI(e) device can directly access the memory or registers of another PCI(e) device, or main system ram, without regard to where it is located. The PCI(e) bridges route the request to the appropriate device, as they are configured ( by the system firmware/bios, and possibly later by the OS kernel ) to know what address ranges are ...

That if a PCI device wishes to transfer data to a memory address, that address must exist in actual system RAM (and is allocated during PCI configuration) and not virtual memory. So if a PCI device only needs to transfer a small amount of data at a time, where there is no advantage to putting it into RAM or using DMA, then I/O addressing is ...

I understood that a PCI Express endpoint device may have some memory BAR mapped in the system memory (is it always RAM the system memory we are talking about?). I need to understand what happens when I send from the CPU to the device (A) a memory read request, addressing a certain memory address (first memory BAR, offset 0).

It doesn't have to be located in physical RAM, and for I/O devices it is not usually located in RAM. It just uses physical RAM addresses, addresses that then cannot be used for anything else even if there is real RAM in these addresses. In your example, if the device intercepted the address, then yes, the OS had better use a non-existent ...

2020年4月26日 · Note that it is not CPU RAM per say, it is the RAM on the northbridge that is available to the CPU as well as PCI-E (or whatever other devices on the northbridge). The GPU used to be a PCI device on the southbridge and the bus would be limiting, but I think modern GPUs are PCI-E. Also, DDR (RAM) is not as fast as GDDR (graphics).