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Topic Summary

Posted by: DanEE
« on: May 25, 2020, 21:29:30 »

I think we are arguing over semantics. Yes technically the processor does not talk to memory directly. I was speaking at an abstract level. Intel has one Integrated Memory Controller (IMC) in the mobile PC parts. Intel's documentation in volume 1 of the Ice Lake datasheet states it can be run in Single or Dual channel Mode. The ark website lists the maximum number of memory channels as two for the Ice Lake parts. They were not going to change to documentation for LPDDR4 to say aggregated channels or something like it. That is what I was referring to.
I suspect the only reason that Intel added "sub channels" and AMD added "virtual channels" support is to get boards to route without adding layers and cost. The floor planning of the die and ball assignments are designed in SOC's to make it easier to route for two separate channels with single channel devices or DIMMs. The trace length matching, specified in pico-seconds, for pairs, bits in a lane and between lanes is very tight. To have the buses cross would be a nightmare to route. I did many DDR and LPDDR designs over the years.
The Comet Lake U parts support LPDDR4x and not LPDDR4 and datasheet says 2 64bit wide channels. The LPDDR4x spec added a single channel option, where as all LPDDR4 parts were dual channel. It doesn't have the sub channels or their associated register definitions. It will one or two 64bit bus(es) in a LPDDR4x configuration.
LPDDR4/x can be added in parallel to form any width. The UM433IQ uses 4 32bit (2, 16bit channels) LPDDR4 to make 4 32bit channels. It really is a routing and cost issue.
It will be interesting to see what happens with LPDDR5.
Posted by: Valantar
« on: May 22, 2020, 11:36:27 »

@Valantar Okay, same as Ice Lake. Intel refers to them as sub-channels. The processor still runs single or dual channel modes only.
That is a meaningless statement. The CPU doesn't interface directly with the memory, it interfaces with the memory controller(s). The single- or dual-channel indications generally mean either one or two controllers is in use. When each controller for LPDDR4X can run two channels, the setup is quad channel even if the CPU fails to correctly identify it as such due to the controller effectively aggregating two 32-bit channels into one 64-bit interface. If the CPU was running single or dual channel LPDDR4X, you would halve memory bandwidth, as there is no such thing as a 64-bit wide LPDDR4X channel. The distinction is largerly academic, but given that there are no LPDDR4X chips with a wider interface than 32 bits, that must be what determines the effective number of channels, not the number of controllers in use.
Posted by: Dan EE
« on: May 22, 2020, 08:15:20 »

@Valantar Okay, same as Ice Lake. Intel refers to them as sub-channels. The processor still runs single or dual channel modes only.
Posted by: Valantar
« on: May 22, 2020, 07:04:09 »

@Valantar Where did you get the information that the Ryzen mobile has 4 memory channels? I would be very surprised if it did. Every thing I have read is that it is dual.
The one good thing about getting it with a single channel 8GB SODIMM is that you only have to buy one more to increase it to 16GB. Not something the average user will do. It should have either 2x4GB or 2x8GB modules as options.
@Debra - What to recommended depends on what you are using it for and how long you plan on keeping it. Home business and meeting with customers, school with light gaming, photoshop, web developement, casual use... No simple answer, however I think the Ryzen 4000 mobile has it all over the Intel mobile right now.
It has two memory controllers, each of which can function as a single 64-bit wide DDR4 channel or two (virtual, as they are running off the same controller) 32-bit wide LPDDR4X channels. (Source: Anandtech) Both of course add up to the same total channel width. This setup allows LPDDR4-equipped laptops to not be hobbled by the narrower channels of the mobile-first memory tech (which can even go down to 16-bit channels for applications like smartphones). Thus, total peak bandwidth is higher for the higher clocked LPDDR4X.
Posted by: Dan EE
« on: May 22, 2020, 01:27:40 »

@Valantar Where did you get the information that the Ryzen mobile has 4 memory channels? I would be very surprised if it did. Every thing I have read is that it is dual.
The one good thing about getting it with a single channel 8GB SODIMM is that you only have to buy one more to increase it to 16GB. Not something the average user will do. It should have either 2x4GB or 2x8GB modules as options.
@Debra - What to recommended depends on what you are using it for and how long you plan on keeping it. Home business and meeting with customers, school with light gaming, photoshop, web developement, casual use... No simple answer, however I think the Ryzen 4000 mobile has it all over the Intel mobile right now.
Posted by: Miker345
« on: May 21, 2020, 22:19:51 »

Per page 14 of the user manual, it has two SODIMM slots with max memory of 32GB. It comes with 1 x 8GB slot filled. It has only HDMI 1.4, USB C Gen 1. The DisplayPort version is not specified and is usually 1.2 when the port is Gen 1.
It only comes with a 220Nit 45% NTSC panel. That is the show stopper for me.

I also contacted dell to confirm and they said that is correct, so the article itself is incorrect. But I agree with comment about the display. I would have purchased if the display was at least average.
Posted by: Debra S Barkle
« on: May 21, 2020, 21:21:19 »

So which tablets and laptops would you recommend,  each in the $800 range?
And why?
What about no cost limitations?
Posted by: Valantar
« on: May 21, 2020, 10:26:44 »

Yeah, that's a stupid configuration that definitely leaves a lot of performance on the cutting room floor..make it LPDDR4X..
ddr4 is the fastest, low power ddr4 is the efficient.
what you said..makes no sense whatsoever.
That is simply not true. DDR4 at best hits 3200MT/s in mobile implementations, with baseline latencies in the ~20 cycle range. LPDDR4X hits 4266MT/s, so 33% higher bandwidth (given equivalent total channel width, which Renoir offers through its choice of 2x64-bit DDR4 or 4x32-bit LPDDR4X), though with somewhat worse latency. While there are absolutely consumer workloads that are RAM latency dependent and would thus lose some performance, iGPU performance is almost entirely RAM bandwidth limited, so any increase is worth the tradeoff if that's what you're looking for. The same goes for other bandwidt-limited CPU workloads like compression/decompression. Also, the increased frequency does to a certain extent alleviate the latency disadvantage even if it doesn't erase it entirely (CAS 20 at 3200MT/s (1600MHz) = 0,0125s absolute time CAS latency vs. for example CAS 40 at 4266 MT/s (2133MHz) = 0,0188s or 33% better latency rather than the 100% it looks like from the specs).

So, tl;dr: no, DDR4 is not faster than LPDDR4X. It can be in a limited selection of tests, but overall it is slower.
Posted by: asldkf;jls;a
« on: May 21, 2020, 01:48:51 »

Yeah, that's a stupid configuration that definitely leaves a lot of performance on the cutting room floor..make it LPDDR4X..
ddr4 is the fastest, low power ddr4 is the efficient.
what you said..makes no sense whatsoever.
Before you correct someone else you should make sure you actually know what you are talking about. Its explained in the original comment you replied to. LPDDR4X (not LPDDR4) has more bandwidth than DDR4.
Posted by: asldkf;jls;a
« on: May 21, 2020, 01:03:52 »

Single channel memory and a 40 Wh battery? Simply pathetic. Who thinks pairing an 8 core processor with single channel memory is a good idea? Intel must have the best contract lawyers in the world.
Posted by: william blake
« on: May 20, 2020, 19:12:30 »

Yeah, that's a stupid configuration that definitely leaves a lot of performance on the cutting room floor..make it LPDDR4X..
ddr4 is the fastest, low power ddr4 is the efficient.
what you said..makes no sense whatsoever.
Posted by: william blake
« on: May 20, 2020, 18:53:37 »

so... amd 14 is a better choice over intel 13?
dell, unlike some others, made the amd-only model and the intel-only model? intriguingly.
Posted by: Dan EE
« on: May 20, 2020, 18:19:59 »

Per page 14 of the user manual, it has two SODIMM slots with max memory of 32GB. It comes with 1 x 8GB slot filled. It has only HDMI 1.4, USB C Gen 1. The DisplayPort version is not specified and is usually 1.2 when the port is Gen 1.
It only comes with a 220Nit 45% NTSC panel. That is the show stopper for me.
Posted by: Valantar
« on: May 20, 2020, 13:20:44 »

Yeah, that's a stupid configuration that definitely leaves a lot of performance on the cutting room floor. Soldered RAM is perfectly fine, but then at least make it a sufficient amount (8GB has no longevity even if it's perfectly fine today), make it LPDDR4X, and populate all channels on the controller (IIRC the LPDDR4X configuration is 4x32-bit channels vs. the standard DDR4 2x64-bit).
Posted by: Redaktion
« on: May 20, 2020, 12:58:16 »

The latest device from Dell to feature new AMD Ryzen 4000 APUs is the Inspiron 14 7000 2-in-1 laptop. The convertible can be configured with either a Ryzen 5 4500U or Ryzen 7 4700U processor. Although the prices for the Ryzen 4000 laptops are lower, the more-expensive 13-inch Intel variants offer more RAM and more powerful batteries.

https://www.notebookcheck.net/Latest-AMD-Ryzen-4000-laptops-now-available-from-Dell-New-Inspiron-14-7000-2-in-1-lower-prices-but-still-less-power-than-the-Intel-alternatives.466057.0.html

 
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