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[<< Home](/home#7-interfaces-between-alpaca-and-gbo-infrastructure-panel-charge-6)
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[<< Section 7.1](./7.1)
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## 7.2 Back End Housing, Power, and RFI Shielding
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We propose that the ALPACA digital beamformer back end reside
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in the new GBO data center. We understand that this facility is still
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under construction with an estimated completion in the next year.
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Signal lines from the on-telescope front end will be over 138 optical fibers
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(not including spares) and routed directly to the ALPACA server racks for tray
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management and splicing. The following describes the physical infrastructure
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needs to accommodate this back end.
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### 7.2.1 Server Racks
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The ALPACA digital back end hardware was presented and described in detail in
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[Section 5.3](../5-dbe/5.3) and will be housed in six 44U server racks, each with
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a footprint of 24"x41". These racks have mesh screened doors for front-to-back
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air flow cooling, cable access openings in the top and bottom for routing from
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and to the rack, and removable solid side panels to join multiple rack
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enclosures together. The racks are pictured below.
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<div align="center">
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<img src="../img/dbe/alpaca-racks.png" width="700">
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</div>
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### 7.2.2 F-engine Rack Mount Enclosure
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The enclosure for the Xilinx ZCU216 and 16-channel RX board will be a General
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Devices utility chassis, item number CHA-05-21.
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We have begun adding panel cutouts to the chassis 3D model for electrical,
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optical, and structural connections to the ZCU216 and 16-channel RX board, and
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for supplying power to the unit. Fiber connections for the RFoF downlink to the
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16-channel RX board will be made on the front panel, with ethernet, power, and
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other ZCU216 connections made through the back plate. An image of the chassis 3D
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model with panel cutouts is shown below:
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<div align="center">
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<img src="../img/dbe/rfsoc-enclosure.png" width="500"/>
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Figure: Utility Chassis 3D Model with Panel Cutouts
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</div>
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Physical dimensions of this chassis are given in the following table:
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| Parameter | Specification |
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| :------ | :------ |
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| Overall Height | 5.22 in |
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| Chassis Height | 4.75 in |
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| Chassis Depth | 21.25 in |
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| Overall Depth | 21.47 in |
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Table: General Devices Item CHA-05-21, D-4001, Utility Chassis Dimensions
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### 7.2.3 Power Requirements
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The total power requirement for the ALPACA digital back end is expected to be
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19.25kW. This includes all 25 servers and comprised hardware, 12 ZCU216
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enclosures (supporting receiver electronics, fans, etc.), and 100GbE switch with
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optics. It is proposed that each server rack have a dedicated 30 Amp 208VAC
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supply. The following table shows the power requirements for the various systems
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of the digital back end.
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| Component | Consumption |
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| :------ | :------ |
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| AMD EPYC 7313 | 139W/155W (max) |
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| Memory (8x16GB DDR4) | 22.4W |
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| A10 GPU | 135W/150W (max) |
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| MCX556-EDAT | 19.3W/26.8W (max) |
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| 8 cm fan | 1.92W |
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| SATA HDD | 6.5W (max) |
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| SATA SSD | 2.2W (max) |
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| 100GbE Switch | 1760W/1900W (max)|
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| ZCU216 <br> w/ enclosure electronics| 130W |
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| IB Switch | 75W/122.32W (max)
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| data storage servers | 300W < P < 350W |
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The expected total power requirement for the data storage hardware is 1.3kW.
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This includes the three specified storage servers of [section
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5.4](../5-dbe/5.4) and the IB switch with optics.
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### 7.2.4 RFI Shielding
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No regulatory EMI compatibility measurements or testing of the back end hardware
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have been made. We anticipate however that the self-radiated RFI from both the
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servers and the RFSoCs in their enclosures to be similar levels to each other,
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typical for data centers, and as is common of other digital back ends found in
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GBO facilities. We are expecting that the new GBO data center to be planned and
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built to continue to accommodate non-RFI shielded computing hardware.
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[Section 7.3 >>](./7.3)
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[general-devices]: https://catalog.generaldevices.com/item/cabinet-accessories/d-4001-utility-chassis/pn-1192
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[power-calc]: https://outervision.com/power-supply-calculator |
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\ No newline at end of file |