3 ms·

Why don't they just put ram slots on the card so you can augment the fast ram

VHRanger 7mo ago
GDDR7x doesn't come in dimm factor? In general soldered ram seems to get much higher bandwidth than removeable ram. See ryzen AI Max vs 9950x max ram throughputfor example
- wewewedxfgdf 7mo ago
  We are talking here about slower ram to augment.
- nic547 7mo ago
  Strix Halo uses a 256bit memory interface, the normal desktop processors only have a 128bit interface, that's the biggest difference in bandwidth. For more bandwidth you need to go to a Threadripper. Strix Halo seems to use LPDDR with 8000 MT/s, which is a bit faster than the usual 5600 MT/s-6400 MT/s "normal" DDR5-DIMMs (Albeit (expensive) faster ones seem to exist), so there's a slight edge towards soldered memory (not sure about LPCAMM2 and similar tech). GDDR7 is a different league, a 5070 Ti also has a 256bit memory interface, but has 896GB/s bandwidth, compared to strix halo with 256GB/s
  - VHRanger 7mo ago
    It's really hard to push DDR5 past 6000MT/s on 4+ DIMMs it seems. I had to get everything top spec to fit 4 channels of 6000MT/s on my 9950x (asus proArt motherboard and the top tier trident neo RAM sticks) -- otherwise it's reportedly unstable.
    - nic547 7mo ago
      9950X is dual channel, running 4 DIMMs runs them interleaved, with two DIMMs sharing one physical connection, impacting signal integrity severely. AFAIK this has gotten worse with DDR5 to the point that it's generally recommended to avoid 4 DIMMs unless you really can't get enough RAM otherwise. For maximum bandwidth you need to avoid interleaving. Strix Halo simply has more memory controllers. Threadrippers are also quad channel, and should be able to run 4 DIMMs at rated speeds, but the cheapest Zen 5 Threadripper seems to be almost double the price of a 9950X3D.
      - VHRanger 7mo ago
        And I presume that doubled price is before you look at the workstation class motherboards, which also tend to be much more expensive. Thanks for the info on the hardware quirks, useful to know! We seem to be arriving at a cambrian explosion of viable hardware these days between ARM and x86, soldered vs DIMM, etc. It's refreshing coming from 20 years of x86 being all that matters.
- adrian_b 7mo ago
  No. All GDDR memory is intended only for being soldered around a GPU chip, on the same PCB. This is how they achieve a memory throughput that is 4 to 8 times higher than the DDR memories used in DIMMs or SODIMMs.
timmmmmmay 7mo ago
connectors are bad for signal integrity and GDDR is particularly picky about this
- wewewedxfgdf 7mo ago
  We're talking about ordinary RAM to augment, like a cache. Not as GPU VRAM expansion.
M95D 7mo ago
Speed and reliability. A connector of any kind reduces signal quality. Data lines need to be longer, because the memory slot won't fit under the radiator where the memory chips are now, and that adds even more electrical interference and degrades signal. Also, we had memory slots on '90s cards. They were extremely expensive and proprietary. Ever saw a Matrox VRAM card? I never did.
- HighGoldstein 7mo ago
  > A connector of any kind reduces signal quality. Like the M.2 connector? > Data lines need to be longer Like the data lines going all the way to an on-motherboard storage device?
  - zbentley 7mo ago
    > Like the M.2 connector? Yes, though likely something with a higher pin count since memory access is more likely to be random and can be parallel versus block storage. > Like the data lines going all the way to an on-motherboard storage device? Yes. Why would a GPU manufacturer/packager take on that cost, if it’s presently served well enough for most people by offloading it onto other parts of the system?
  - literalAardvark 7mo ago
    Soldered stuff is still dramatically better than the M2 connector (than any connector really). You've never wondered why RAM doesn't use PCI Express?
  - adrian_b 7mo ago
    The current DIMM and SODIMM modules cannot be used for much higher speeds than are available now. This is why there are several proposals of improved forms for memory modules, which use different sockets, like LPCAMM2, which should be able to work with faster memories. However even LPCAMM2 is unlikely to work at the speeds of soldered GDDR7.
    - varispeed 7mo ago

GDDR7x doesn't come in dimm factor? In general soldered ram seems to get much higher bandwidth than removeable ram. See ryzen AI Max vs 9950x max ram throughputfor example

wewewedxfgdf 7mo ago
We are talking here about slower ram to augment.
nic547 7mo ago
Strix Halo uses a 256bit memory interface, the normal desktop processors only have a 128bit interface, that's the biggest difference in bandwidth. For more bandwidth you need to go to a Threadripper. Strix Halo seems to use LPDDR with 8000 MT/s, which is a bit faster than the usual 5600 MT/s-6400 MT/s "normal" DDR5-DIMMs (Albeit (expensive) faster ones seem to exist), so there's a slight edge towards soldered memory (not sure about LPCAMM2 and similar tech). GDDR7 is a different league, a 5070 Ti also has a 256bit memory interface, but has 896GB/s bandwidth, compared to strix halo with 256GB/s
- VHRanger 7mo ago
  It's really hard to push DDR5 past 6000MT/s on 4+ DIMMs it seems. I had to get everything top spec to fit 4 channels of 6000MT/s on my 9950x (asus proArt motherboard and the top tier trident neo RAM sticks) -- otherwise it's reportedly unstable.
  - nic547 7mo ago
    9950X is dual channel, running 4 DIMMs runs them interleaved, with two DIMMs sharing one physical connection, impacting signal integrity severely. AFAIK this has gotten worse with DDR5 to the point that it's generally recommended to avoid 4 DIMMs unless you really can't get enough RAM otherwise. For maximum bandwidth you need to avoid interleaving. Strix Halo simply has more memory controllers. Threadrippers are also quad channel, and should be able to run 4 DIMMs at rated speeds, but the cheapest Zen 5 Threadripper seems to be almost double the price of a 9950X3D.
    - VHRanger 7mo ago
      And I presume that doubled price is before you look at the workstation class motherboards, which also tend to be much more expensive. Thanks for the info on the hardware quirks, useful to know! We seem to be arriving at a cambrian explosion of viable hardware these days between ARM and x86, soldered vs DIMM, etc. It's refreshing coming from 20 years of x86 being all that matters.
adrian_b 7mo ago
No. All GDDR memory is intended only for being soldered around a GPU chip, on the same PCB. This is how they achieve a memory throughput that is 4 to 8 times higher than the DDR memories used in DIMMs or SODIMMs.

timmmmmmay 7mo ago

connectors are bad for signal integrity and GDDR is particularly picky about this

wewewedxfgdf 7mo ago
We're talking about ordinary RAM to augment, like a cache. Not as GPU VRAM expansion.

M95D 7mo ago

Speed and reliability. A connector of any kind reduces signal quality. Data lines need to be longer, because the memory slot won't fit under the radiator where the memory chips are now, and that adds even more electrical interference and degrades signal. Also, we had memory slots on '90s cards. They were extremely expensive and proprietary. Ever saw a Matrox VRAM card? I never did.

HighGoldstein 7mo ago
> A connector of any kind reduces signal quality. Like the M.2 connector? > Data lines need to be longer Like the data lines going all the way to an on-motherboard storage device?
- zbentley 7mo ago
  > Like the M.2 connector? Yes, though likely something with a higher pin count since memory access is more likely to be random and can be parallel versus block storage. > Like the data lines going all the way to an on-motherboard storage device? Yes. Why would a GPU manufacturer/packager take on that cost, if it’s presently served well enough for most people by offloading it onto other parts of the system?
- literalAardvark 7mo ago
  Soldered stuff is still dramatically better than the M2 connector (than any connector really). You've never wondered why RAM doesn't use PCI Express?
- adrian_b 7mo ago
  The current DIMM and SODIMM modules cannot be used for much higher speeds than are available now. This is why there are several proposals of improved forms for memory modules, which use different sockets, like LPCAMM2, which should be able to work with faster memories. However even LPCAMM2 is unlikely to work at the speeds of soldered GDDR7.
  - varispeed 7mo ago