On this occasion, it runs through the block twice in order to access the same amount of data as the initial step. Next it runs through the same block again, except this time it accesses every fourth value and so makes four passes. And so on, until a certain maximum step size is reached. The size of the block of memory used for this test is one quarter the amount of system RAM or MB, whichever is smaller. Memory Speed Per Block Size When a computer program wants to use a section of memory to store data, it makes a request to Windows for the amount of memory it requires.
Windows allocates the memory to the program unless system resources are very low and returns to the requesting program the address of the first memory slot in the allocated block. It is recommended to let the system remain idle, close all unnecessary programs, and let it run as long as possible. Here you can choose different settings like problem size, RAM Memory test size, and specify run count or run time. In Run Count the process is run a specified number of times and in case of run time the test is run for a specified time duration.
Under the settings tab, you can specify the mode which may be either 32 bit, or 64 bit. Priority class option may be set to idle, below normal, normal, above normal, high, and real time in this RAM tester. If the option is chosen, it automatically stops when error is encountered.
MemScope is a simple RAM checker software that can be used to perform PC memory test and identify any problems encountered. You can choose the RAM test option to run either a single test or run all the tests. You can pause the RAM test at any time and resume from the same location again. Error summary of different RAM tests is also displayed.
In case any error is encountered, it shows the test, pass, failing address, expected bits, actual bits, and Xor bits. For example, suppose you decided to use the following test algorithm: write the value 1 to the first location in memory, verify the value by reading it back, write 2 to the second location, verify the value, write 3 to the third location, verify, etc.
Since each read occurs immediately after the corresponding write, it is possible that the data read back represents nothing more than the voltage remaining on the data bus from the previous write.
If the data is read back too quickly, it will appear that the data has been correctly stored in memory-even though there is no memory chip at the other end of the bus!
To detect a missing memory chip the test must be altered. Instead of performing the verification read immediately after the corresponding write, it is desirable to perform several consecutive writes followed by the same number of consecutive reads. For example, write the value 1 to the first location, 2 to the second location, and 3 to the third location, then verify the data at the first location, the second location, etc.
If the data values are unique as they are in the test just described , the missing chip will be detected: the first value read back will correspond to the last value written 3 , rather than the first 1. If a memory chip is present but improperly inserted in its socket, the system will usually behave as though there is a wiring problem or a missing chip.
In other words, some number of the pins on the memory chip will either not be connected to the socket at all or will be connected at the wrong place. These pins will be part of the data bus, address bus, or control wiring.
So as long as you test for wiring problems and missing chips, any improperly inserted chips will be detected automatically. Before going on, let's quickly review the types of memory problems we must be able to detect. Memory chips only rarely have internal errors, but, if they do, they are probably catastrophic in nature and will be detected by any test. A more common source of problems is the circuit board, where a wiring problem may occur or a memory chip may be missing or improperly inserted.
Other memory problems can occur, but the ones described here are the most common. By carefully selecting your test data and the order in which the addresses are tested, it is possible to detect all of the memory problems described above. It is usually best to break your memory test into small, single-minded pieces.
This helps to improve the efficiency of the overall test and the readability of the code. More specific tests can also provide more detailed information about the source of the problem, if one is detected.
I have found it is best to have three individual memory tests: a data bus test, an address bus test, and a device test. The first two test for electrical wiring problems and improperly inserted chips, while the third is intended to detect missing chips and catastrophic failures.
As an unintended consequence, the device test will also uncover problems with the control bus wiring, though it cannot provide useful information about the source of such a problem. The order in which you execute these three tests is important. The proper order is: data bus test first, followed by the address bus test, and then the device test.
That's because the address bus test assumes a working data bus, and the device test results are meaningless unless both the address and data buses are known good.
If any of the tests fail, you should work with the board's designer to locate the source of the problem. By looking at the data value or address at which the test failed, he or she should be able to quickly isolate the problem on the circuit board. Data Bus Test The first thing we want to test is the data bus wiring.
We need to confirm that any value placed on the data bus by the processor is correctly received by the memory device at the other end. The most obvious way to test that is to write all possible data values and verify that the memory device stores each one successfully.
However, that is not the most efficient test available. A faster method is to test the bus one bit at a time. The data bus passes the test if each data bit can be set to 0 and 1, independently of the other data bits. A good way to test each bit independently is to perform the so-called "walking 1's test. The name of this test, walking 1's, comes from the fact that a single data bit is set to 1 and "walked" through the entire data word. The number of data values to test is the same as the width of the data bus.
This reduces the number of test patterns from 2n to n, where n is the width of the data bus. Since we are testing only the data bus at this point, all of the data values can be written to the same address. Any address within the memory device will do.
However, if the data bus splits as it makes its way to more than one memory chip, you will need to perform the data bus test at multiple addresses, one within each chip.
To perform the walking 1's test, simply write the first data value in the table, verify it by reading it back, write the second value, verify, etc. When you reach the end of the table, the test is complete. It is okay to do the read immediately after the corresponding write this time because we are not yet looking for missing chips.
In fact, this test provides meaningful results even if the memory chips are not installed! It assumes that the caller will select the test address, and tests the entire set of data values at that address. If the data bus is working properly, the function will return 0. Otherwise it will return the data value for which the test failed. The bit that is set in the returned value corresponds to the first faulty data line, if any. In addition, the system uses individual level settings and data-bus inversion DBI to maximize throughput in testing high-speed devices.
This enables quick and efficient development of new test programs, which reduces the demands on customers' resources while also improving the time to market for new semiconductor designs.
The system's real-time source-synchronous function enables high throughput. Additionally, an advanced timing-training capability helps to identify the most effective test solution faster than other systems on the global market.
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