Question Does all DDR5 (4800 or faster) have a JEDEC 4800 profile?

Dave3000 · Apr 22, 2025

I recently upgraded my secondary system from an MSI H610M-G DDR4 WiFi with 32 GB Crucial DDR4-3200 to an MSI B760M Mortar WiFi II with 32 GB Crucial Pro DDR5-6000 (It was cheaper with a price-match than the 32 GB Crucial 5600 kit that wasn't cheaper even with a price-match). Now my plan was to run the RAM no faster than JEDEC DDR5-4800 which is the maximum officially supported speed of the IMC of the i5-12400 in the system and I expected it to default the DDR5 to 4800. It defaults the DDR5 to 5600. Also I had to disable a SPD write setting in the BIOS to get Thaiphoon burner to detect SPD information in this DDR5 otherwise it would give me a popup saying something like the SMI controller could not be detected and to disable SPD write in the BIOS, so I did that and now Thaiphoon burner detects the SPD information and it does show a 2400 setting with it's associated timings along with the other common JEDEC speeds and their timings. However, the BIOS won't default to the 2400 one which really means 4800 MT/s for DDR5. I didn't update the BIOS yet. Now my question is, does all DDR5 have a JEDEC 4800 profile and if the CPU's IMC only officially supports up to JEDEC 4800, should the BIOS default it to JEDEC 4800, basically should all RAM be backwards compatible with slower speeds than the advertised speed? The advertised JEDEC speed for this RAM is 5600, but should it also be backwards compatible with 4800? Is there a setting to make it default to the 4800 JEDEC profile for the DDR5 installed in the system since the IMC of the CPU I have installed will officially support up to DDR5 4800?

Dave3000 · Apr 22, 2025

I tested the Crucial DDR5-5600 RAM from my main system (which defaults it to DDR5-5200 for my Ryzen 7 7800X3D) to my secondary system which defaults it to DDR5-5600 for my i5-12400 like the DDR5-6000 I just purchased. I thought the the memory controller on the CPU determines what speed the RAM will run at default memory settings if the module supports that speed, at least on other PC's I built it was that way and I had to manually enable XMP or manually tweak the memory settings if I want to run outside the CPU's specifications. Also I tested this DDR5-6000 I just bought on my main system and it defaults at the CPU memory controller's maximum officially support memory speed which is 5200 for the Ryzen 7 7800X3D in this case. So I guess returning the RAM to the store for the standard DDR5-5600 which is the same brand and series that I'm using on my main system, except 32 GB sticks on my main system and 16 GB sticks on my secondary system, won't do me any good especially when this kit I got a little cheaper than the standard kit. Does this sound like a BIOS issue with the motherboard that is defaulting the RAM to 5600 for my i5-12400? I could manually set it to DDR5-4800 but I don't know what the secondary timings should be for JEDEC 4800 speeds, they are obviously not the same as the secondary timings for JEDEC 5600 speeds.

zir_blazer · Apr 22, 2025

Two things:

Modules have a SINGLE standard JEDEC SPD profile and a possible supported CAS Latency table. All the other valid slower clock speeds/timmings below it for backwards compatibility are calculated from those two.
The original Thaiphoon Burner website was a gold mine about this kind of info (1, 2).

EVERY LGA 1700 motherboard that has 4 DDR5 slots should default, AT MOST, to 4400 MHz (Lowest possible is 3600). Alder Lake 4800 MHz and Raptor Lake 5600 MHz only applies to 1 SPC (2 slots) boards, yet both supports only up to 4400 MHz on 2 SPC (Slots per Channel) boards even if populated with a single DIMM. Even your intended 4800 is technically overclocking because it is above Intel specifications.

If Motherboard decides to set them to 5600 out of the box without enabling XMP, BIOS is being funny, since it should check which is the slowest component and set things accordingly. You could try lowering DRAM Frequency to 4400 since it should auto calculate the rest of the timmings manually without having to input them manually if you leave them in Auto.

Dave3000 · Apr 22, 2025

I tried setting the DDR5 frequency to 4800 manually but the timings don't automatically change and I must manually input them. I would have no problem finding out what the first 4 timings are for JEDEC 4800 but the rest of the timings I would not know what to set them to for JEDEC 4800. Thing is it automatically sets it to JEDEC 5600 and at 1.1v which is the advertised non-EXPO and non-XMP timing of this kit which is still considered an overlock of the IMC of the i5-12400 CPU since this CPU officially supports up to JEDEC DDR5 4800 MT/s and any higher than that is and overclock, even if it's a JEDEC timing and voltage. I wonder if this board, mine in particular, by default is looking for the highest JEDEC profile programmed in all DDR5 modules, regardless of what the IMC of the CPU officially supports. I also flashed to the first BIOS released for this motherboard and it still is having this issue. At least I know the modules in this kit have a JEDEC 5200 profile as I tested them in another system I have as I mentioned here earlier and they defaulted to JEDEC 5200 on that system.

zir_blazer · Apr 23, 2025

Dave3000 said:
I tried setting the DDR5 frequency to 4800 manually but the timings don't automatically change and I must manually input them. I would have no problem finding out what the first 4 timings are for JEDEC 4800 but the rest of the timings I would not know what to set them to for JEDEC 4800. Thing is it automatically sets it to JEDEC 5600 and at 1.1v which is the advertised non-EXPO and non-XMP timing of this kit which is still considered an overlock of the IMC of the i5-12400 CPU since this CPU officially supports up to JEDEC DDR5 4800 MT/s and any higher than that is and overclock, even if it's a JEDEC timing and voltage.

It seems that you ignored the part where I said that for 2 SPC boards like your new MSI B760M Mortar WiFi II the maximum is NOT 4800, just 4400. Check the Intel datasheet yourself.

No idea why your BIOS does that. I think it is the first time I hear about a board defaulting to overclock the RAM.

Dave3000 · Apr 23, 2025

zir_blazer said:
It seems that you ignored the part where I said that for 2 SPC boards like your new MSI B760M Mortar WiFi II the maximum is NOT 4800, just 4400. Check the Intel datasheet yourself.

No idea why your BIOS does that. I think it is the first time I hear about a board defaulting to overclock the RAM.

You said that the board is defaulting to overclock the RAM but this is genuine JEDEC DDR5-5600 as checked by Thaiphoon burner, especially with a CL latency of 46 and 1.1v DIMM voltage at that speed and that's what my motherboard defaults to for this CPU, but it also has XMP/EXPO profiles for tighter timings but with higher DIMM voltage at 5600 or 6000 which would be basically factory overclocked profiles of the RAM that it is rated for. You said my motherboard is overclocking the RAM but It's technically not overclocking the RAM, but overclocking the IMC on the CPU's memory controller by default. It's the first time I hear about the B760 chipset using over DDR5-4400 on 2 SPC motherboards is overclocking. The specifications for this motherboard on the back of the box and on the manufacturer's website don't mention this. I also tried standard JEDEC DDR5-5600 modules and it still did the same thing by default. Even at Crucial's website it states that DDR5 memory of higher speeds should downclock to support systems that only support lower speed DDR5 in their specifications. I'm using 1 slot per channel (DS A2 and DS B2) on this motherboard.

Dave3000 · Apr 24, 2025

In Thaiphoon Burner, it shows a table of frequencies which are JEDEC, EXPO, and XMP, in that order, after reading the SPD of the modules. Are all those JEDEC frequencies actually programmed in the SDP of the modules I have installed in the system or is it just there as general reference? I'm asking this because CPU-Z shows only 4 profiles in its SPD section of the program, and they are all the XMP and EXPO one but not the JEDEC ones, and my motherboard's BIOS is not defaulting to the 2400 MHz (DDR5-4800) CL 40 profile that is shown in the table, which is the maximum official stock spec for my i5-12400 in this system, and instead defaulting to the 2800 MHz (DDR5-5600) CL 46 profile. I'm now using Crucial Pro DDR5 5600 modules.

Question Does all DDR5 (4800 or faster) have a JEDEC 4800 profile?

Dave3000

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Dave3000

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