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Questions tagged [dma]

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Extending the kernel's 4MB limit for memory allocations using DMA api - dma_alloc_coherent

I'm using Ubuntu 16.04, and I'd like to use dma_alloc_coherent to allocate a DMA buffer (non-cached) that is larger than 4MB. When I attempt to do this, the call returns a NULL. I've tried the kernel ...
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CrystalDiskInfo showing an UltraDMA CRC Error Count of 5 - Have I lost any data?

CrystalDiskInfo tells me I have an UltraDMA CRC Error Count of 5. Does it mean I've lost data or that I have corrupted files on my hard disk ? Or were those 5 errors corrected ?
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Hardware protection against bit-flips during I/O between storage and DRAM?

If a motherboard supports ECC DRAM, then it has a 72 bit bus between the DRAM slot and the memory controller. 64 data bits + 8 parity bits for SECDED. Nowadays, most CPUs have the memory controller ...
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1answer
929 views

Un-allowed DMA capable bus/device(s) detected

My problem is how can I find out which device on my laptop is Un-allowed DMA capable. I tried disabling my USB devices and unplugging laptop from docking station. My colleague has same laptop model ...
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1answer
375 views

I can't change SATA hard disk (working in UDMA) to PIO mode in Linux

I'm trying to disable DMA in my SATA 3.5" hard disk drive to work in PIO mode because for recovering some bad sectors from a failing disk with GNU ddrescue I am using PartedMagic Linux live CD and I ...
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27 views

Size of one DMA block

When DMA is used, the whole block of memory is transferred from I/O device to main memory. I am interested in the size of this block, more specifically in the answers to these questions: Is the size ...
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Location of Windows video memory

I'm currently analyzing a KVM solution. For this purpose I would like to locate the Windows video memory which is used by the KVM probably using DMA. Is there a way to achieve this? The system is ...
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How to implementing a application with Linux DMA

As far as I know, Linux provides common DMA framework for various DMA engine and a device driver for DMA engine have to be implemented based on the the framework. Is the framework provide any system ...
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127 views

Monitoring DMA Performance in Windows?

Why DMA is not listed in windows performance monitor's available counters? RDMA Activity is already present but not DMA. Is it possible to monitor DMA in windows?
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5k views

DMA settings in Windows 10

My Acer Aspire One 2GB has suddenly started running as slow as molasses. It can sometime take up to a minute to open a program. Googling around I see that my HD may have switched from DMA to PIO after ...
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117 views

Is latency from hardware interrupts a hardware, driver or kernel issue?

Being a power user I have spent countless hours tuning systems, checking DPC latency blah blah All of this begs the question why are we still dealing with these issues? I personally can't tell if ...
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3k views

Are few UDMA_CRC_Error_Count errors in an SSD an issue?

Some SMART stats: Device Model: Samsung SSD 850 EVO 500GB Firmware Version: EMT01B6Q 9 Power_On_Hours 0x0032 099 099 000 Old_age Always - 252 12 ...
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How do I enable DMA on a SATA controller?

I don't see any section "IDE ATA/ATAPI controllers" in device manager: What does this mean? and Can I know on which devices DMA can be enabled?
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IOMMU cache coherency

In today's x86/x64 motherboards there can be found IOMMU's from Intel and AMD. They allow peripheral devices to perform DMA (direct memory access) operations into system RAM using virtual instead of ...
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116 views

When doing IDE DMA on x86, can other CPUs access the memory?

I am unfamiliar with hardware. I am studying the IDE disk I/O and DMA on x86. I want to know that when doing a IDE disk I/O with DMA, can other CPUs access the memory (or exactly, the same memory ...
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2answers
1k views

Virtual Memory and MMU: when are they used and when not?

I'm wondering about how a Virtual Memory system could be managed alongside with a MMU when there's the need to mantain some "fixed" addresses in the address space. For example, when a machine boots ...
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1k views

PCI Express BAR memory mapping basic understanding

I am trying to understand how PCI Express works so i can write a windows driver that can read and write to a custom PCI Express device with no on-board memory. I understand that the Base Address ...
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1answer
136 views

How to stress the Windows XP kernel?

We have intermittant problems with writing DVDs where the writing process fails. We suspect that the problem is happening when the DVD driver switches from DMA mode to PIO mode and then in this mode ...
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1answer
187 views

Debian loses harddisk on bootup 4 times and then boots. Why?

Dmesg Dump: http://paste.debian.net/44975 at time 32.832045 That error is delaying my boot process significantly. Does anyone know what this is about? Devices: Maxtor IDE drive with new cable on ...
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1answer
347 views

Debian Wheezy, old computer, DMA read error, scales modes down until PIO

I got an old computer that I wanted to install debian wheezy on. Well that works but,at every bootup I get those errors: ata1.00: failed command: READ DMA when it happens the kernel softresets the ...
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1answer
1k views

Kernel bypass possible with non-specialised NIC?

Is it possible to perform kernel bypass and have a NIC send data to the user space (where I will write my network stack) with no copying, without having to purchase a specialised Solarflare etc NIC?
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1answer
113 views

DMA issue, keyboard about to die?

I have this message when I boot up debian and it takes a bit before booting when it reaches this error message: https://dl.dropboxusercontent.com/u/762638/Files/Images/dma_issue.jpg If I mount the ...
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1answer
59 views

IDE DMA sector numbering

I'm just playing around with the QEMU system emulator, and taking a look at the IDE disk emulation, specifically at the DMA disk accesses. I'm a little confused as to how DMA requests are actually ...
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2answers
3k views

When a disk read or disk write occurs, where does the data go?

I understand that there is such a thing as a disk controller which contains a buffer, but was wondering if the CPU reads directly from this buffer, or whether the data must first go to a specific ...