What Does Flex Mean by 4X CPU Power in 8XXX Radios ?

Russ Ravella

Probably the most valuable feature in the 8XXX is expanded processing power for future growth (assuming that future growth actually occurs). Flex's 8XXX roll-out presentation claims they have 4X the processing power.

My understanding is, the 6600 has 2X the processing power of the 6400 enabling twice the number of slices. And the 6700 similarly has 4X.

Is the 4X Flex is claiming for the 8XXX 4 times that of the 6700 ? Because if it's only 4 times that of the 6400, its apparently not actually any more powerful than the 12 year old 6700.

73 Russ KR6W

Neil D Friedman N3DF

I don’t think CPU processing power equates to the number of slices produced.

Russ Ravella

Hi Neil,

Yeah, it's not clear to me that it does either - at least not linearly. But I've heard it explained that way so I don't know. Hopefully someone knowledgable at Flex will address the question and explain what 4 times the power does actually mean.

73 Russ KR6W

Trucker

As far as I know, they are referring to the on-board processors that run the embedded Linux system. FPGA also has more internal processing ability than the older generation of FPGA. Another plus, is the demise of the SD card for storage. That should improve performance as well. I am hoping that Flex Radio has secured a long term supply of all the components to sustain the new line of radios.

Practically speaking though, I imagine it will be difficult for any manufacturer to keep sufficient stock of critical components for several years. The world of electronics keeps evolving and, it seems to me, a difficult problem to overcome for all but the largest of companies. It is a reflection on the mindset of today's consumer. We want the latest and greatest now. And once the new wears off,it's on to the next new thing. Older hams like myself, don't necessarily feel the need for the latest and greatest. But, I know younger people do feel that way. And for any company to stay competitive, even in a niche market like Amateur radio, manufacturers need to keep new things coming to keep the attention of the buyers.

James

WD5GWY

Russ Ravella

Hi James,

Yeah, they do seem to be referring to the on-board processor. What I'm asking is, "4X what ?".

73 Russ KR6W

fpmacko

Hi Russ,

When they say "4X" they're probably referring to the number of DSP resources available on the new FPGA parts that they're sourcing for the 8xxx series. (Perhaps also a higher clock speed but I doubt if they're saying that the clock is four times faster than the old part.) 4X is a subjective metric based on how one perceives what 1X comprises.

As reference, take a look at the datasheet for the FPGA used in the 6700.

https://docs.amd.com/v/u/en-US/ds150

I believe Flex were using the XC6VLX130T part.

BTW, it's also pretty common to purchase the IP for an ARM processor and instantiate it right on the FPGA. So, you probably won't find a discrete "CPU" in any Flex radio except for maybe something in the TI DaVinci core if they're still using that.

73….Frank / WA3NHK

Russ Ravella

Hi Frank,

Thanks for the response !

I'm thinking they're referring to DSP resources too but my understand (for what it's worth which ain't much …) is they are divided into those in the FPGA as you mentioned and those in conventional CPU processing. They explicitly state the increase in FPGA processing is "2X". Then say the increase in CPU processing is "4X". And what I'm asking is what do THEY mean by "4X" ? 4X compared to what ? An explanation of how that will translate into functionality even subjectively somehow would be great too.

In my case, there's going to have to be something pretty amazing eventually in the 8XXX to cause me to give up my 8-slice 6700. I certainly didn't expect to care about 8 slices but it only took about a day of having them to never want to go back (I upgraded from my third 6600 trying to find something - anything - that was reliable).

In a recent post, Eric said they haven't totally given up on eventually releasing an 8-slice radio and I'll probably hold out for that until the end. But if anything could persuade me, it would be some real no-kidding utilization of that additional power. The features they've described so far are pretty unremarkable.

73 Russ KR6W

Steve-N5AC

Addressing multiple points here:

1. In the world of FPGAs, there are "hard cores" and "soft cores." Hard cores are designed into the silicon, metallization layers, etc. and are functions that come integral to the part that cannot be reprogrammed. Typical things that are done this way are networking or serializer interfaces, clocking such as PLLs, microprocessors, memory controllers, etc. Xilinx, the vendor we use most often for FPGAs (now owned by AMD), offers FPGAs with both with and without hard processors. The processing they offer in their parts is insufficient for the load we place on the processors (not enough horsepower). Soft processors, those that are loaded into the FPGA fabric at runtime, are necessarily slower than hard processors. There are many reasons for this including such things as propagation of a clock signal across FPGA fabric, limited capability to duplicate all the transistors in a processor, etc. So we also rarely use soft processors. From an architecture standpoint, FlexRadio uses discrete processing and FPGA components. This allows us to "mix and match" with best-in-breed solutions and also pay the lowest cost (incidentally, FPGA vendors want to charge a premium for included processing resources over what those parts cost by themselves in the market).
2. The "4X" refers to a substantial increase in the baseband processing capability of the radio. As someone else mentioned, all prior FLEX-6000 radios used the TI DaVinci processor (TMS320DM8168CYG2/4 for those that want to look at the part) as the baseband processor. Some radios used the faster 4 variant (6700 for example) while some used the slightly slower 2 variant (6300 for example). The FLEX-8000 transitioned to a 4-core ARM A72 processor. The new processor moves the radio internally from 32 to 64-bits and substantially improves performance. With our basic tests, we see about 4X the power with the new processor.
3. We also mentioned about a 2X increase in the FPGA power. This is a larger, faster part than we were using before. FPGAs aren't really rated anything like processors are and looks can be deceiving. You need a pretty good understanding of how you're going to use an FPGA in order to understand what each one or it's capabilities might do in your application. FPGAs have different kinds of blocks in them that do different things, also known as "resources." The resources you need for different kinds of operations varies based on what you're doing, how much of the workload is similar to other parts of the workload, how much you can pipeline and/or multiplex your workload, what the Fmax (fastest clock speed) is that you can operate at, etc.
4. The number of slices that we put in a radio comes from a number of factors. Performance is one factor; FPGA resources is another. We're just getting going on this platform and so we decided to start with what we had before. But it's a software defined radio, folks. Who knows what we might decide to do in the future. More hardware allows us to add software; more software can do more things.

Steve

Trucker

Very informative explanation Steve. It goes a long way in helping me understand a little better about the internal working of our radios. I am still far behind the curve on understanding. But, your explanation does help.

James

WD5GWY

Russ Ravella

Steve, thanks for the response.

It sounds like you're saying the horsepower in the 8400 and 8600 are the same (ARM A72 and whatever "FPGA components" are being used in the new larger, faster part), the difference in CPU horsepower between the 6300 and 6700 was "slight" so the "2X" and "4X" numbers could be said to be relative to either, and that the new 8XXX level of processing may be sufficient to support an 8-slice variant in the future without further h/w upgrades. Do I have that right ?

One question: regarding your comment "… start with what we had before.", that included the 8-slice 6700, right ? Flex's flagship radio. Why couldn't it have been part of this new start ?

73 Russ KR6W