EXE is using the Hard Drive format and is designed to be directly executed from Windows environments. ZoneT. View PDF. Posts / Dell Community / Desktops / Desktops General - Locked. HK980 UW457 CT107 I use the procesor AMD Athlon 64 X2 Dual-core. Which upgrade available for this cpu with same motherboaed Dimension E520 cpu. 5 (39) $4899. 3 FlexBay drive Can contain an optional floppy drive or optional Media Card. 3 Posts. 4GHz Dual-Core Socket F OSA2216GAA6CX CPU Processor is not compatible with the Dimension C521. CheyannTx. Start a Conversation. Isn't their more of an limited choice on upgrade parts for that. 1st time i booted - everything ran normally. 0. dell dimension c521. Download and install the latest drivers, firmware and software. 0G, 512K, 62 Watt. Bev. Windows Vista, 32-bit. When I check the sounds and audio devices menu, in the control panel, it says there is no audio device installed. I Have a Dell Dimension C521 using Vista 32bit. Dell File Name: DME521-010111. Dell Support Driver and Downloads not offering manual downloads for my XPS 8940. Title: Dimension E521 Setup Diagram Author: Dell Inc. The Dell Dimension series was a line of home and business desktop computers manufactured by Dell. 0 GB -Technology: DDR II SDRAM Storage: -Hard Drive: 320. 0Ghz 89W Windsor has 64-bit support. and I went to Upgrade to. 5GB RAM 128mb ATI Radeon X1300 Low profile card (ordered a XFX HD 4350 512MB which should be delivered Wednesday) Motherboard Dell - Phoenix - Award WorkstationBIOS v6. d e l l . No,you need another Dell OEM E521 motherboard, the Dell Dimension E521 has a BTX chassis and motherboard, there are no compatible BTX retail motherboards available. . Can someone give me an idea as to what type of memory I need for my Dell. 1. Overview. (probably closer to a 300 wat considering how Dell rates them) so you will be very limited on what, if any, video cards you can use. 0Ghz 89W Windsor, will work. I am not planning to play any games, I only want to. Fast & Free shipping on many items!. Re: Dell Dimension C521 will not start up No diagnostic lights and a good power supply is indicative of a bad motherboard, and Dell motherboards are proprietary meaning a standard ATX board won't line up in the case correctly. 2 out of 5 stars 11. 0 connectors (2) Model DCSM w w w . 2007. HERE are the driver downloads for the C521. I was wanting to upgrade my Dell Dimension C521 computer. Normally I would use System Restore to fix this but system restore was turned off. Page 1 Dell™ Dimension™ C521 FlexBay for optional floppy drive or Media Card Reader headphone connector microphone connector diagnostic lights cover release latch card slots for PCI (1), PCI Express x1 (1) PCI Express x16 (1) Model DCNE w w w . I had 3gb DDR2 ram installed, i have amd x64 dual core processing, nvidia geforce 8400GS graphics. RAM: 2GB. 80GHZ INTEL PENTIUM 4 NORTHWOOD CORE 533MHZ FSB, 1GB OF RAM (512 PCR2700), (512 PCR 3200), 80GB MAXTOR DIAMONDMAX PLUS 9 HARDDRIVE-MASTER, 320GB WESTERN DIGITAL HARDRIVE - SLAVE; NVIDIA GEFORCE FX 5200 PCI @ 256MB, 845GV CHIPSET; MODIFIED COOLING SYSTEM @ 2 80MM FANS, 1 PCI SLOT COOLING. The Dell Recovery partition will absolutely NOT install on non-Dell Hardware. Unsolved. (I have a Dimension 3000 and a Dimension 4600, and have researched the entire line. A few hours ago I did a hard reboot (held the power button down until it shut off), which I have done many times before, and now it wont turn back on. When I rang Dell technical support, they ask for a service tag which the monitor does not. Firstly, let me tell you what make/model it is: Dell Dimension C521 The computer was working grand up until yesterday. I somehow lost the connection and now get NO AUDIO OUTPUT DEVICE INSTALLED. Publish date: 09 MAR 2007. . The e521 does not use a Dell proprietary power supply. 0. com Dell™ Dimension™ C521 Benutzerhandbuch FlexBay für optionales Diskettenlaufwerk oder Medienkartenlesegerät Festplattenanzeige Netzschalter Mikrofonanschluss CD/DVD-Aktivitätsanzeige CD/DVD-Auswurftaste Diagnoseanzeigen USB 2. [quotemsg=10213451,2,237355]The motherboard/socket determines the CPUs that can be used. Dimension C521 no booting. The PCI-e x16 would be where an add-in video card would be installed, unless this system is using on-board graphics. [quotemsg=11316617,0,926132]Hi guys I wanna help my dad upgrading his dell dimension C521 (slim case) mostly the graphics card. 22. Dell Dimension C521 Upgrade. it has the hy175 mainboard. com (em inglês) Dell™ Dimension™ E521 Manual do proprietário Modelo DCSM FlexBay para unidade de disquete ou leitor de cartão de mídia opcional luz de atividade da unidade de disco rígido conector do microfone conector de fone de ouvido luz de atividade da unidade de CD ou DVD botão de ejeção do CD ou DVDUnplug any USB devices. 04-04-2009 09:00 AM. If I upgrade to the 256MB ATI x1300 pro graphics card what would be the picture quality difference compared to the NIVIDA GeForce 6150 LE? Is it a separate graphics card? Also, isnt hard to find a video card for the Dimension C521? It isnot a full size desktop. 4 CD or DVD activity light The drive light is on when the computer reads data from the CD or DVD drive. I would like to add an additional SATA 80bgb HDD that. 4 Posts. The file DMC521-010110. 80Ghz 2Mb Am2 Winsor . 0Ghz 89W Windsor, will work. New to Dell Community / Dimension C521 . I have a Dimension C521 that i have changed the motherboard, because the original one was damaged. Storage. Dell Dimension C521 desktop 取扱説明書. I have this problem too (0) Reply. 9. That processor isn't supported by the E521, because it's an AM3 socket. I own and use C521 /E521 Bois version 1. 00. Dell Dimension C521, Ram Issues. 0 連接器 (2) 機箱蓋釋 服務標籤 放閂鎖 電源按鈕/ 電源活動. 1. Once the computer rebooted it got to the Windows splash screen and stayed there for about 10 minutes. com Dell™ Dimension™ E521 Manuel du propriétaire Modèle DCSM Baie modulaire pour lecteur de disquette ou de carte (en option) Voyant d’activité du disque dur Connecteur de microphone Prise casque Voyant d’activité du lecteur de CD/DVD Bouton d’éjection du CD/DVD Voyants de diagnostic Connecteurs USB 2. Download and install the latest drivers, firmware and software. This post is more than 5 years old. Posted by: tom. Download and install the latest drivers, firmware and software. I am working on a Dimension E521 32-bit Windows XP machine and I am trying to upgrade to Windows 7. Diagnose an issue or test pc for your Dell Dimension C521. Dell Dimension C521. -Dell Dimension E521 -305 p. and lists keys and their functions within the active system. Installation Instructions. This product is a pretty fast machine, i purchased it just a few days ago and its much much faster than my previous computer, oh my goodness. 25-04-2017 06:00 AM. i looked on yahoo and found out that other people with a dell dimension C521 had the mouse issue to. 4 out of 5 stars 3. Jan 23, 2013. DellFile Name: DME521-010111. Comment pouvons-nous vous aider à trouver LXun 280W Power Supply Compatible with Dell OptiPlex GX520 GX620 740 745 755 210L 320 330/Dimension C521 3100C GX280 (P/N: MH595 MH596 NH429 NC912 RT490 L280P-01 D235PD-00 D280P-00 H280P-00) 4. I have checked each stick indivually and all four work fine. Back to Contents Page Replacing the Computer Cover Dell™ Dimension™ C521 Service Manual CAUTION: Before you begin any of the procedures in this section, follow the safety instructions located in the Product Information Guide. I've noticed some cards are identified specifically for the Dell Dimension computer (like: VIA VT6421A IDE & SATA RAID PCI Card For DELL Dimension). Documentation. Bev. 89 GB. Format Description: This file format consists of a BIOS-executable file. 0. And yes I have the latest drivers for. I have a Dell Dimension C521 with a keyboard problem: Keyboard works during boot and in BIOS. Add to Buddy List. Subject: Setup Guide Keywords: esuprt_desktop#esuprt_dimension_desktops#Dimension C521#dimension-c521#Setup Guide Created Date:Reinstall all USB devices, check cable connections, and then restart the computer. Your Dimension C521 supports these operating systems: Change Product. 1. . Restart the computer. Identify and fix common problems with online dell diagnostics. Along with sound and modem drivers, I suspect you failed to install the Intel chipset drivers, which define what is on the motherboard. The chipset drivers MUST be installed. Okay, in the guide, it sais ::: 1. The newer Athlon IIs require a socket AM2, AM3, or AM3+. AMD Athlon 64 3200+, 2. There's no beeps from it and nothing comes up on the monitor either. Recommended. In 2007, the Dimension series was discontinued and replaced with the Dell Inspiron series for low-end models and the Dell Studio series for higher-end models. If that doesn't help, reinstall the two chipset drivers listed on the Dell Downloads HERE, restart the PC and then reinstall the SigmaTel drivers again. I thought that maybe the updates did something, so i decided to try a. I have this problem too (0) Reply. itgforlife. 3 2 ratings. and then immediately pulled it because it caused the system to. So owners of C521, wait for this card to come out, don't rush and buy any Radeon X1600 or Geforce 7600GS. I have a 2. dell. 34. Amd Athlon64 X2 6000 3. My current desktop (dell dimension c521) is currently having some problems every time i turn it on it has a yellow light instead of a green light this has been happening for some time now but i used to give it a few turn on and off`s when it was yellow and it would go green but now it just stays yellow and of course im no computer. Unsolved. 0. Please click the link mentioned. by Dell Technologies. 5" Laptop drive in a Dimension e521? Bev. MG. I can't really recommend any particular PSU models, but a Dell PSU replacement will generally be around $50, and a cheap PSU should be in the $20 range. Basically, the one thing you need to worry about buying a PCI video card, are the card's power requirements compatible with the Dimension C521 280watt power supply. 5 processors but wich one is intalled on my stock E521 computer. Dell Dimension C521 woes. )It makes no difference, a video card's memory, is separate from the computer, a card with 512MB 64-bit DDR3 [or what ever] will work fine. 11 is installed, with BIOS version 1. To use it, download the file and copy it to a DOS-bootable USB flash drive, then boot the system to the USB flash drive and run the program. Solution. install the desktop system software & chipset drivers before installing any other drivers after you put XP Pro on that c521. 1. The tower makes the usual start up noise, i can hear the fan start, but then it stops and it all goes quiet when the monitor fails to turn on. I Applied the latest bios update from dell web site (at this time 2-feb-07) and still not working. Download file to Desktop The file DMC521-010003. Your Dimension C521 supports these operating systems: Change Product. Enter. If you replace the battery, a 3-V CR2032 lithium coin cell is needed, this can be purchased from a Radio Shack, WalMart, or most pharmacies, etc. 0. When USB is plugged in, boot stalls and takes an extra 2 minutes to complete. 1 Update BIOS. 4. com Dell™ Dimension™ C521 Manual do proprietário Unidade de disquete ou Leitor de cartão de mídia para FlexBay opcional Luz de atividade do disco rígido Botão liga/desliga Conector do microfone Luz de atividade da unidade de CD ou DVD Botão ejetar da unidade de CD ou DVD Luzes de diagnóstico Conectores USB. dell dimension c521 Start a Conversation. But when i put the same harddrive in my Dell XPS 410, it boots with no problems. and lists keys and their functions within the active system. The specs of Computer shows full configuration information. Vijay2U. 0 GB - Standard - Serial ATA -Optical Storage: DVD-ROM Monitor: 19. $4. 48 delivery Sep 22 - 26. Unsolved. Up to 500GB 7200RPM. 4 System BIOS. Dell Desktops Community Support Forums all models. While it is true that the Dell OEM windows checks for a BIOS signature, it does NOT prevent you from installing windows on non-Dell Equipment. The Dimension E521 Computer only supports AMD Athlon 64 X2 / Athlon 64 / Sempron. The PSU in the C521 is rated at 280W however I have seen posts both here and elsewhere online that say that Dell always under-rate their PSUs. I heard that AMD proceesors have a cool & quiet feature. Posts / Dell Community / Desktops / Desktops General - Locked. 4 System BIOS. Dimension C521 System BIOS. 0 連接器 (4) We would like to show you a description here but the site won’t allow us. d. Please click the link mentioned below which will take you to the drivers website: I Need to know if the following models of motherboards are compatible with my Dimension C521. 0 connectors (4) The Dimension C521 is Dell's next generation of workhorse office PC system and comes with an Athlon 64 3800 processor, an ATi X1300 GPU, 1GB of DDR2 RAM and runs Windows Vista Home Premium,. Chop off the 5 pin connector and the new fan connector. Eligible for Return, Refund. 3 Posts. 00. I currently own a Dell Dimension C521, i bought 2 and a half years ago. The fan noise is loud and the power button remains lit amber/orange, but nothing occurs. 2 Service Tag Use to identify your computer when you access the Dell Support website or call support. The install then continued from 21% until the final reboot. Download. 4 Legacy. Subject: Setup Guide Keywords: esuprt_desktop#esuprt_dimension_desktops#Dimension C521#dimension-c521#Setup Guide Reinstall all USB devices, check cable connections, and then restart the computer. Dimension C521 I get a blank screen and the fan starts going to hyperspeed (Loud). I'm having the same problem with my Dell Dimension E521. When I turned it on this morning the power light stays amber, doesn't go green and the fan inside the computer goes at full blast. I going to add more ram and was looking for advise on other processors, but I guess I will go back. 5 Floppy. I have a 5 year old Dimension C521 running Vista Home Basic. jake007 . Or fastest delivery May 17 - 19 . 2010-11-15 18:15:44. com for dell dimension c521. The Dimension E521 and C521 area the slim and the tower "identical" systems. I was asked to download the new BIOS and did so according to the instructions, but now I am having trouble. Dimension C521 Manuel du propriétaire Date de publication: 09 MAR 2007. Posts / Dell Community / Desktops / Desktops General - Locked. Long story short I would like to install a video card on my Dell Dimension C5. You'd be better off starting from scratch with a new build. Dell Dimension C521 Video U. EXE. 1. 55 $ 16. Prior to installing the processor, check that you have BIOS Version 1. angieb1. Finally read elsewhere to remove 2GB RAM from 4GB setup so that system only had 2GB. Eligible for FREE Economy Shipping When In Stock. This post is more than 5 years old. The Dimension E521 L1 cache is 64 kilobytes in size, while its L2 cache is rated at either one or two. Due to it's age [9/10 years], replacement E521 motherboards will be 'refurbished' [aka used] and could be the same age as your system, with a very limited warranty. Dell Technologies Dimension E521. The Dimension e521 supports internal 3. 5" SATA, 7200rpm hard drives, similar to THIS Curious, but how did you manage to install a 2. 10-05-2009 17:00 PM. The unit was purchased in Apr 2007 so it is out. Dell Dimension C521 Dell Dimension E310 Dell Dimension E510 Dell Dimension E520 Dell Dimension E521 Dell Dimension XPS Gen 3 Dell Dimension XPS Gen 4 Dell Dimension XPS Gen 5 Dell Inspiron 1090 (DUO) Dell Inspiron 11 3000 Series (3147) Dell Inspiron 11 3000 Series (3148)hello, I have a dell dimension 9100 with Microsoft Windows XP Home Edition Service Pack 2 (Build 2600). 4GB (2GBx2) Team High Performance Memory RAM Upgrade For Dell Dimension E510 E510n E520. 1. The ports are automatically enabled during the POST (Power On Self Test) and if they do not work, there are three possibilities (1) the board is defective (2) the BIOS is corrupted (and in that case the board is no good as there is no way to recover from a corrupted BIOS) (3) The CMOS (BIOS) needs reset. . 6) Connect it like this: FAN: Yellow -> DELL: White. 4GHz, 512K) with 4 GB DDR2 SDRAM. | support. After the power was restored, I could not get my computer to load anything. S. Get drivers and downloads for your Dell Dimension C521. 04-01-2010 11:00 AM. S. 1. The Dell Optiplex GX280 Dimension 8400 Copper CPU Cooling Heatsink W4254 0W4254 shown in your link, is not compatible with the Dimension e521 that is a BTX system, not ATX and requires a UX521 - Heatsink & Shroud Assembly, same as. UBUNTU 6. These caches are known as the L1 and L2 caches. The following is a list of known supported Dimension C521 processors: AMD Sempron 3400+, 1. 96 GHz. Dell typically uses custom connectors between motherboards and front panels. This system has one low profile PCI slot where you could install a WiFi card assuming nothing else is using that slot (eg, add-in audio card -it does have onboard audio- or a modem). lbiswim. The diagnostic lights do not light up nor does the power switch. To get the data off the drive you can install it in any PC (that has the correct controller Sata or IDE depending on the drive you have) with or hard drive enclosure to get the data off of it. I turned it back on and the power light is solid amber and nothing shows up on my monitor at all. SupportAssist for PCs. com Dell™ Dimension™ E521 Manuel du propriétaire Modèle DCSM Baie modulaire pour lecteur de disquette ou de carte (en option) Voyant d’activité du disque dur Connecteur de microphone Prise casque Voyant d’activité du lecteur de CD/DVD Bouton d’éjection du CD/DVD Voyants de diagnostic Connecteurs USB 2. Check with Dell Support, their on-line documentation, diagnostics, and ask in. If you are experiencing any issues, you can manually download and reinstall. Did that, created a new C and D drive, and installed Windows XP Professional. I. Get parts and accessories upgrades for your Dell Dimension C521. View PDF. 5G, 1MX2, Dual Core, 65Watt should work fine in the dimension c521. BIOS. Create New Topic. 2 Service Tag Use to identify your computer when you access the Dell Support website or call support. Along with sound and modem drivers, I suspect you failed to install the Intel chipset drivers, which define what is on the motherboard. I have an dimension C521 desktop running Windows XP Home addition with SP3. Dell Desktops Community Support Forums all models. Hi there, My wife's Dimension C521 just died, or more specifically, the screen faded to black over a period of about ten seconds. This past weekend, I finally got around to trying to upgrade my Dimension C521 to Windows 7. I have an dimension C521 desktop running Windows XP Home addition with SP3. 2GB Dell Dimension E310 E510 E520 E521 4700 RAM Memory. Note regarding operating systems not listed above: Dell may not support an operating system for various reasons, including discontinued support from the software vendor, lack of availability with certain products. In my Dell is a AMD 64 Athlon X2 4200+ 2,2GHz installed. I have a Dimension C521 which will not start. Check out the product website. Dimension C521 Service Manual Publish date: 09 MAR 2007. I have a Dimension C521 which won't POST, due to a failed BIOS update. My new one has AMD Athlon 64x2 processor 3800+ 2. EDIT: MY PROBLEM HAS BEEN FIXED. Start a Conversation. Processor: Intel Intel Core 2 Duo E6320 5000+ / 1. Super low-noise performance upgrade with SATA HDD & PCI-EXPRESS Video Support for Dell Dimension 5150 5100 E510 E520 E521 3100 E310, Dell PowerEdge 800 830, DELL Part# MC633, PC357, N8372, NC905, C5201, and PH333 H305N-00. Sorry for my english. | support. Or fastest delivery Fri, Apr 14. Insert the new battery into the socket with the side labeled "+" facing. DELL CN-0HY175 REV A03 Socket AM2 DIMENSION C521 Motherboard. 20151. 12821. At this point I'll see if the PCI slots are vacant/available and try to buy a SATA card for the slot. | support. Download. 0 why are my videos still playing slow or only part way and serching?? Please advise. 2010-11-15 18:15:44. This thread is locked. 1 Channel Audio). 933. A flashing amber light, in most cases is a power supply failure. Start a Conversation. 2 Intern. com Dell™ Dimension™ C521 Owner’s Manual FlexBay for optional floppy drive or Media Card Reader hard drive activity light power button microphone connector CD or DVD activity light CD or DVD eject button diagnostic lights USB 2. Bev. 24-10-2006 13:00 PM. If that does not help, reset the CMOS by removing the motherboard battery for several seconds. Just be sure to install it right side up--you can read the label. Remove the jumper plug from pin 1. 00 $ 54. just got a brand new Dimension C521,Athlon 64 X2 5000 running vista home ed. The Serial PS2 Port Adapter from Dell ™ adds PS2 functionality to your system. Dimension C521 『セットアップ図』 Author: Dell Inc. Hello. 15494. Dell Desktops Community Support Forums all models. Dimension E521 Setup Diagram Publish date: 01 JUL 2007. ETC, basic standard C521, w/ added ram/video card. 86 GHz RAM: -Installed Size: 2. If you are experiencing any issues, you can manually download and reinstall. Solved! Go to Solution. It just stay in this screen after the dell logo. 0. I am asking because Dell's own description of the C521 is that it is mainly for basic daily tasks like e-mail and web browsing so I just wanted to be sure before purchase! Many thanks in advance ;-) Message Edited by. So unless you -or somebody else- has mapped the connector in the c521 case, you may not be able to install a different Dell (or non-Dell) motherboard in this case. 1. Afficher le PDF. I bought this machine second-hand with no hard drives or Operating System/Driver discs. just got a brand new Dimension C521,Athlon 64 X2 5000 running vista home ed. Products; Solutions & Services;. Get drivers and downloads for your Dell Dimension C521. This problem started the other day without warning. 4 Posts. Find the best download for your system Please enter your product. Download and install the latest drivers, firmware and software. Download Other BIOS drivers, firmware, bios, tools, utilities - Page 21次に、コンピュータをコンセントに接続しなおし、電源を入れて dell ロゴ表示中に f2 キーを連打し、セットアップユーティリティを起動します。セットアップユーティリティに表示される日付と時刻が間違っている場合、バッテリーを交換します。Dell Dimension c521 GPU upgrade Post Date: 2011-08-24: Post Reply . Find Members Posts. System Setup Options. There are no diagnostic lights illuminated on front panel. HK980 UW457 CT107 I use the procesor AMD Athlon 64 X2 Dual-core. Identify and fix common problems with online dell diagnostics. And when it did boot into Windows, the USB mouse would lockup. RobinBredin. . roryfla. The BTX arrangement places the CPU right at the front of the case. Dimension C521 1. thetechguyuk10. Dell DImension E521 with XFX Radeon HD 5670 - Random No Signal/Standby Hi When I installed the graphics card mentioned in the subject line, after perhaps 15 (the incident is very random and difficult to know for sure) reboots all of a sudden I get a 'no signal' message on my Asus VW225 display and it then switches to standby. 8 Mhz. dell. if exist other compatible model of motherboard, please. The CPU fan runs slow for about 2 seconds, then goes turbo. Along with the ATI Radeon X1300 Pro graphics, it's more than powerful enough to run Vista in full-blown Aero. Parts & Repairs. Find the best download for your system Please enter your product. When I try to boot it, the fan comes on and is really loud, but the monitor doesn't power on. 0 connectors (4) Manage your Dell EMC sites, products, and product-level contacts using Company Administration. Dimension E521 1. i purchase new graphic card evga geforce gtx 970 4gb ssc 04g-p4-3979 to replaced nvidia geforce gt 730It' attached to their Dell Dimension E521 which I'd bought them in the previous year. 11-06-2009 22:00 PM. Dimension E521 1. 3. Try disconnecting the power cord, then push the power button in and hold it for about 15/20 seconds, reconnect the power card and see if this makes a difference. 1. Dimension C521 CPU upgrade I've got a C521 that is running a stock AMD Athlon 64 X2 3800+, and would like to upgrade the CPU to be able to edit HD videos. Post the issue in the appropriate Board, where they will be answered. Small Business. . CMS 2GB (2X1GB) Memory Ram Compatible with Dell Dimension C521 Desktop - A100. Newer revisions often don't work with the 'better' AM2 cpu's than what was originally offered with the E521/C521 platform. Did you enabled on the BIOS, if not go and do this. 08-12-2007 20:00 PM. Dell Dimension E521 Running Windows 10. Dell Dimension E521 (Athlon64 2. 2. 1038. sparker781. Download and install the latest drivers, firmware and software. Restart your system and keep tapping 'F8' as soon as the Dell logo appears. If the computer starts normally, reinstall an additional module. Its smaller. com Dell™ Dimension™ C521 Manuel du propriétaire Baie modulaire pour lecteur de disquette ou lecteur de carte en option Voyant d'activité du disque dur Bouton d'alimentation Connecteur de microphone Voyant d'activité du lecteur de CD/DVD Bouton d'éjection du CD/DVD Voyants de diagnostic Connecteurs USB 2. dell dimension c521. BIOS Release Title: BIOS: Dell Dimension System BIOS, English, Dimension C521, 1. 15-04-2012 04:00 AM. Afficher le PDF.