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RAMCHECK's USE OF PAGE BURST MODE
This Application Note discusses the use of Page
Burst mode by RAMCHECK for high speed memory testing.
What is the Full Page Burst Mode?
Full Page Burst mode is a setup of an SDRAM device to burst a full page per each data access. It is available on many SDRAM devices but not in all of them in order to speed up the transmission of a continuous group of data. It is activated by setting the Burst Length control bits (A2..A0) of the SDRAM's Mode Register to '111'. It is very important to note that PC motherboards DO NOT use full page burst access, and that this mode is not specified in PC133/100/66 standards. Therefore, a PC133/100/66 device may not support Full Page Burst and is still perfectly acceptable by such standards.
Further, the DDR devices, which are the next evolutionary step of SDRAM technology, do not support Full Page Burst at all.
The Benefits of Using Page Burst Mode by RAMCHECK
Full Page Burst mode allows very fast testing of the memory array, as each access can read or write from 256 locations. This is why we have developed our SDRAM test engine in RAMCHECK (and its predecessor, SIMCHECK II) to utilize this mode of operation.
Also, the ability of the SDRAM to Page Burst at various frequencies provides a good indication to measure maximum operational frequency with a margin.
At the end of Basic Test, the maximum Page Burst frequency is indicated on the screen and in the Test Log. There is also a message if Page Burst was automatically disabled by the test program or if it was disabled by the user.
Page Burst Disabling
As mentioned above, Full Page Burst mode is not being used in actual PC applications. In fact, many SDRAM manufacturers do not include this mode in the device, or only have partial implementation (that is, they do not test this function). As a result, RAMCHECK must be able to detect at the start of the test if full Page Burst can be used. If there is a partial implementation of this mode, RAMCHECK tries to detect this and automatically disable the Page Burst mode. Unfortunately, RAMCHECK cannot always determine if encountered errors are due to a real memory array problem or a Page Burst artifact. This is why our tech support recommend that users will disable Page Burst in cases of unexplained speed drift.
At frequencies of 133MHz and above, we have recently found that modules based on two banks seem to load our test engine in a way that causes intermittent errors that drifts the frequency from 133MHz to 112MHz. To avoid this problem, we have changed our test algorithm from Version 2.11E, and we now disable Page Burst test for all 133MHz modules having two banks.
Since Full Page Burst is not part of the PC133/100/66 standards, we allow a quick disable of this feature using the Change-On-The-Fly feature, or using Setup. The Change-On-The-Fly is called by pressing F2 during Basic Test. Next press F5 for NEXT, pressing F4 will toggle full page burst on and off.
Setup is called by F2 during STANDBY. Press F5 for NEXT, F1 for CONFIG, F5 for NEXT, F1 for SDRAM, F3 to toggle this feature.
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