# How To Allocate PL DDR4 on RFSoC4x2 in PYNQ 3.0.1 **URL:** \ **Category:** Support\ **Created:** [May 16, 2023, 1:34am UTC](https://discuss.pynq.io/t/how-to-allocate-pl-ddr4-on-rfsoc4x2-in-pynq-3-0-1/5586 "2023-05-16T01:34:01Z")\ **Posts on this page:** 1\ **Showing post:** 3
**Author:** ![JennySmith888](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.pynq.io/jennysmith888/32/1966_2.png) [@JennySmith888](https://discuss.pynq.io/u/JennySmith888)\ **Post date:** [May 18, 2023, 6:46pm UTC](https://discuss.pynq.io/t/how-to-allocate-pl-ddr4-on-rfsoc4x2-in-pynq-3-0-1/5586/3 "2023-05-18T18:46:57Z")
Thanks for your response @njachimi. I’m a little confused about a two things. First: > The RFSoC4x2 PS and PL DDR4 memory are both 8GB and same components. They are both 4GB per the [product page](https://www.xilinx.com/support/university/xup-boards/RFSoC4x2.html). Do you mean together the PS and PL DDR4 make up _one_ 8 GB memory? I think in your MTS project the DDR4 range should be 4G not 8G and instead of `reg = <0x10 0x00 0x02 0x00>;` in your `.dts` it should be `reg = <0x10 0x00 0x01 0x00>;`. With your project, I am able to erroneously allocate 8 GB of PL DDR4. If I do two separate 4 GB buffers, they are the same as in if I write to one buffer, the changes are reflected in the other. Maybe there is a reason for this I’m not seeing. The second thing is that **in my project with a different DDR4 base address I have not been able to allocate the memory on the 4x2.** Details: In my project the PL DDR4 is at `0x500000000` and so the register specification for the reserved memory node should read` <0x05 0x00 0x01 0x00>`. I recompiled the `.dtbo` with this new specification and added it to the device tree using the [insert\_dtbo.py](https://github.com/Xilinx/Kria-PYNQ/blob/main/dts/insert_dtbo.py). I appened `python3 /usr/local/share/pynq-venv/pynq-dts/insert_dtbo.py` to the `pynq_venv.sh` startup script which [worked for me on the ZCU111](https://discuss.pynq.io/t/pynq3-0-1-allocate-ddr4-returns-buffer-outside-of-address-range/4918/7). I think what I did should have worked but `allocate` is returning this error. ```auto buff1 = pynq.allocate(int(1.5*1024**3), dtype=np.uint8, target=ol.capture.ddr4_0) ``` ```auto --------------------------------------------------------------------------- RuntimeError Traceback (most recent call last) Input In [3], in () ----> 1 buff1 = pynq.allocate(int(1.5*1024**3),'u8',ol.capture.ddr4_0) File /usr/local/share/pynq-venv/lib/python3.10/site-packages/pynq/buffer.py:158, in allocate(shape, dtype, target, **kwargs) 156 if target is None: 157 target = Device.active_device --> 158 return target.allocate(shape, dtype, **kwargs) File /usr/local/share/pynq-venv/lib/python3.10/site-packages/pynq/pl_server/xrt_device.py:156, in XrtMemory.allocate(self, shape, dtype, **kwargs) 145 def allocate(self, shape, dtype, **kwargs): 146 """Create a new buffer in the memory bank 147 148 Parameters (...) 154 155 """ --> 156 buf = _xrt_allocate(shape, dtype, self.device, self.idx, **kwargs) 157 buf.memory = self 158 return buf File /usr/local/share/pynq-venv/lib/python3.10/site-packages/pynq/pl_server/xrt_device.py:104, in _xrt_allocate(shape, dtype, device, memidx, cacheable, pointer, cache) 102 bo, buf, device_address = pointer 103 else: --> 104 bo = device.allocate_bo(size, memidx, cacheable) 105 buf = device.map_bo(bo) 106 device_address = device.get_device_address(bo) File /usr/local/share/pynq-venv/lib/python3.10/site-packages/pynq/pl_server/xrt_device.py:410, in XrtDevice.allocate_bo(self, size, idx, cacheable) 408 bo = xrt.xclAllocBO(self.handle, size, xrt.xclBOKind.XCL_BO_DEVICE_RAM, idx) 409 if bo >= 0x80000000: --> 410 raise RuntimeError("Allocate failed: " + str(bo)) 411 return bo RuntimeError: Allocate failed: 4294967295 ``` I checked the device tree using `dtc -I fs /sys/firmware/devicetree/base` and sure enough I see my memory node in there: ```auto reserved-memory { ranges; reserved { reg = <0x05 0x00 0x01 0x00>; }; }; ``` The address returned in the `allocate` error message is `0xffffffff `. I’m not totally sure what to make of that. Please let me know if you spot any issues with my approach. P.S. I did try to just change my DDR4 base address to `0x1000000000` to match yours but the address editor was giving me errors related to “memory aperture”. I think it’s not compatible with the rest of the IP I have in my design on the same network? ![image](https://us1.discourse-cdn.com/flex019/uploads/pynq1/original/2X/a/a9287b3038972f8a25323bd41d51f48cf00551f0.jpeg) --- _[View the full topic](https://discuss.pynq.io/t/how-to-allocate-pl-ddr4-on-rfsoc4x2-in-pynq-3-0-1/5586)._