After being in the Flex-ready computer business for the past 8 months, I have gained a lot of experience. Over the last 6 months I have probably tested 30 motherboard/cpu combinations, primarily to find cheaper/better/faster machines for the Flex. I would say 20 of them have been intel-based platforms and the other 10 AMD-based.
Here are some of the things I have "learned": On the intel-based motherboard category, I would say I could get 1 in 6 to work at my acceptable level (avg 20us DPCs). I cannot find a real rhyme/reason for it. The Intel boards seem to layer IRQs on top of each other so you will see an IRQ for a Primary root device and under that will be pci devices with their own IRQs and you can see a lot of high-speed devices assigned to the same root device IRQ but having a dedicated IRQ at the device level. I honestly do not know if IRQ contention at the root device level could cause an issue or not but its my practice to disable everything not in use. But I have only found a couple of boards in the Intel world I could get down to 20us. At the ATX board size, the P7T55D asus board is king of the hill in terms of price/performance. With the i7 860 cpu, the right ddr3 memory and windows XP, you can see stretches of time where the DPC level is 0! It easily is the fastest computer I sell and sub-20us averages are normal. With Win7, the DPCs go up but nothing like on AMD-based machines, its still in the 20-40 range. But I have seen quite a few boards where I could not get a dedicated IRQ and even when I could, I could not get even XP's DPCs down below 90 reliably. I could never figure out why but after an evening of trying, I would put it back in the box and wait until I needed to build a test server or something. By the way, a machine that gives you an average of 90us is still a good machine for Flex radios. Its just that I figure if I can provide a machine that does better at the same or lower price, thats what I will do. CPU-wise, the i9s are definitely the way to go if you can afford it. The newly released i3 cpus are interesting in that they support hyperthreading (which the i7 cpus do not) and they have built-in support for graphics processing, so the motherboards that support i3s are leveraging Intel's latest direction towards integration of GPUs and CPUs on one chip. I have an Intel motherboard/i3 510 setup on the workbench right now and its performance is interesting but still much more expensive than better performing AMD systems. I haven't looked at the i5 cpus so I don't know how they fit in the overall consumer offering. On the other hand, AMD-cpu boards, especially the ones using AMD northbridge controller chips, are easy as pie. You do not have this Root Device IRQ stacking nonsense and its pretty easy to find ones that give you a dedicated firewire IRQ. I have tried 2 AMD-CPU-based boards that had Nvidea chipsets and one worked and the other didn't. CPUs in the AMD line I find exceptional value are: Athlon 2 X2 250, Phenom 2 X4 945, 955 and 965. You will usually see the 955 and 965 in "black editions" which means they allow tweakers to overclock them, but Flex says no support to overclocked systems and I find no reason to do so, these chips are really fast for the money! One thing to watch out for is that AMD has a habit of changing the manufacturing design of CPUs while retaining the same name, and some cpus can have the same name but different power requirements so will not work on some motherboards. I have an affinity for using ASUS motherboards. I like the way they are designed, the bios setup, the way all of their current boards wire up to the computer case the same way, etc. I find G, Skill and OCZ memory to offer high quality at reasonable prices. I like Western Digital drives and Antec computer cases. I like OCZ Fatal1ty modular power supplies (which allow you to only use connectors that are needed instead of the rats nest of the full set found on non-modular power supplies). They all provide products in the sweet spot of price/performance. They also have very expensive products which I would avoid because more bells and whistles means more stuff to interfere or turn off. I have found Nod32 to be the only "invisible" antivirus. Others have had good reports about AVG but I have not had measurable experience with them. Another topic is memory and memory speeds. Many of you probably don't care to know that memory is sold in type (DDR, DDR2, DDR3), speed and latency. Motherboards pretty much dictate what type and speed you use, but its important to get the fastest memory the motherboard will support with the lowest latency you can. The memory speed/latency is so critical you will find that most motherboard manufacturers will list the memory they say will "work" on specific motherboards. I have found a DPC difference in memory with a CAS latency of 9 versus one of 7 (the difference between 20us and 50-60us). A huge difference can be seen in placing the memory "sticks" in the wrong memory slots on the motherboard, so you defeat the dual or triple memory channels designed into the motherboard by doing so, if the board will even boot up at all. I have, oddly enough, found it more performant to use DDR2 memory than the more modern and supposedly faster ddr3 memory. For some reason, you do not find CAS latency levels of 5 in DDR3 memory like you do in DDR2. Believe it or not, very cheap memory with a high CAS latency is noticeable on a system. If you are going to take the route of buying a big-box store computer, you stand better chances with an AMD system that uses an AMD chipset (750, 780, 790). If you buy an i9 860, 920, 960. etc. type of system, you probably will not have many problems that we can't help you work around because the processors are so powerful (and expensive). If you are building, AMD rules the sub-$200 CPU territory. As I find more systems that work well, I will provide a list of the system parts to any and all! 73 Neal Campbell Abroham Neal Software www.abrohamnealsoftware.com (540) 645 5394 NEW PHONE NUMBER Amateur Radio: K3NC Blog: http://www.abrohamnealsoftware.com/blog/ DXBase bug reports: email to ca...@dxbase.fogbugz.com Abroham Neal forums: http:/www.abrohamnealsoftware.com/community/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
