4 ms·

It's the IBM PC legacy. The won and we've lived with that form-factor now for 40 years. A new PC looks very much like that of 1982. Back in '82 when I started i

It's the IBM PC legacy. The won and we've lived with that form-factor now for 40 years. A new PC looks very much like that of 1982. Back in '82 when I started in robotics tech, we mostly used VME. A super-robust interconnect platform. There is no "motherboard" with VME and similar bus architectures. There is a backplane. Why can't we have the benefits of a physical platform like VME but with the electrical form-factor of PCIe?

dragontamer 4y ago
I had a professor talk about those old systems once. Weren't those systems a bus architecture? Like the backplane wires all shared the same wires so it was possible to keep stringing them along? Modern PCIe, and even USB3, are star networks. Everything directly connects to the northbridge like an Ethernet cable star network connects to a switch. ------- PCIe slots communicate the idea well. There are only so many dedicated wires the northbridge exposes to USB3 or PCIe. This, it makes sense to have those limited wires in the form of PCIe slots or USB3 connectors.
Tuna-Fish 4y ago
An important reason why you cannot have that is that the VME is a shared bus, while PCIe is a very high-frequency LVDS point-to-point system that you absolutely cannot implement on a shared bus.
- willis936 4y ago
  There are fabric backplane solutions such as fibre channel and microtca (leverages pcie or ethernet). There's no reason you can't get benefits from a fabric over point-to-point today, it's just big and expensive.
- intrasight 4y ago
  Like I said - not the electric part but the mechanical part.
- rocket_surgeron 4y ago
  VPX (VITA 46). Think of it like VMEexpress. I use PCIe over VPX every day. https://en.wikipedia.org/wiki/VPX https://en.wikipedia.org/wiki/VPX Please, lord, somebody else outside of aerospace use it so more vendors get involved and availability and basically everything about the entire supply chain gets better through competition.
  - imtringued 4y ago
    I always thought VPX is cool but then again there are no consumer products that use it so it is basically irrelevant.
wmf 4y ago
A backplane and a bunch of additional connectors add cost that the PC market doesn't want to pay.
- techdragon 4y ago
  checks features of motherboard ... additional connectors, yep... PCIe backplane, yep... Having bought both... it is definitely costs they don't want to pay, but not the cost of those features. It's more like industrial grade PSUs and redundancy that get mandated by various specifications and end up reducing the market size which further racks up costs.
  - wmf 4y ago
    PCs could have their own backplane standard that's higher-volume and doesn't require industrial-grade anything, but it would still be too expensive. They sweat every yuan.
    - techdragon 4y ago
      My point was that the economics of higher-volume manufacturing result in eventually subtracting everything to the point that the "backplane" is the motherboard. Early ISA backplanes were passive and you basically just had a PC on an ISA card plugged into the ISA bus, with maybe some extra connectors for power and peripherals. Then PCI backplanes started out this way but quickly gathered enhancements that resulted in the "System Host Board" interface and a special connector for more power and IO to/from the "CPU card" in order to do things like support ISA, PCI, peripherals, and later PCI-X slots. Rather than having the extra complexity of the connectors, the high volume PC market folded all of this "onto the backplane" creating the modern motherboard. It might not be clear unless you know a bit about early computer backplanes like S-50/S-100, STD bus, STEbus, VME bus and the equivalent Passive ISA backplanes... by the 90s this is well underway and we already have motherboards that you could recognise as "a motherboard" and "backplanes" that are noticeably different, having evolutionarily diverged during the 80s under differing economic pressures.

dragontamer 4y ago

I had a professor talk about those old systems once. Weren't those systems a bus architecture? Like the backplane wires all shared the same wires so it was possible to keep stringing them along? Modern PCIe, and even USB3, are star networks. Everything directly connects to the northbridge like an Ethernet cable star network connects to a switch. ------- PCIe slots communicate the idea well. There are only so many dedicated wires the northbridge exposes to USB3 or PCIe. This, it makes sense to have those limited wires in the form of PCIe slots or USB3 connectors.

Tuna-Fish 4y ago

An important reason why you cannot have that is that the VME is a shared bus, while PCIe is a very high-frequency LVDS point-to-point system that you absolutely cannot implement on a shared bus.

willis936 4y ago
There are fabric backplane solutions such as fibre channel and microtca (leverages pcie or ethernet). There's no reason you can't get benefits from a fabric over point-to-point today, it's just big and expensive.
intrasight 4y ago
Like I said - not the electric part but the mechanical part.
rocket_surgeron 4y ago
VPX (VITA 46). Think of it like VMEexpress. I use PCIe over VPX every day. https://en.wikipedia.org/wiki/VPX https://en.wikipedia.org/wiki/VPX Please, lord, somebody else outside of aerospace use it so more vendors get involved and availability and basically everything about the entire supply chain gets better through competition.
- imtringued 4y ago
  I always thought VPX is cool but then again there are no consumer products that use it so it is basically irrelevant.

wmf 4y ago

A backplane and a bunch of additional connectors add cost that the PC market doesn't want to pay.

techdragon 4y ago
checks features of motherboard ... additional connectors, yep... PCIe backplane, yep... Having bought both... it is definitely costs they don't want to pay, but not the cost of those features. It's more like industrial grade PSUs and redundancy that get mandated by various specifications and end up reducing the market size which further racks up costs.
- wmf 4y ago
  PCs could have their own backplane standard that's higher-volume and doesn't require industrial-grade anything, but it would still be too expensive. They sweat every yuan.
  - techdragon 4y ago
    My point was that the economics of higher-volume manufacturing result in eventually subtracting everything to the point that the "backplane" is the motherboard. Early ISA backplanes were passive and you basically just had a PC on an ISA card plugged into the ISA bus, with maybe some extra connectors for power and peripherals. Then PCI backplanes started out this way but quickly gathered enhancements that resulted in the "System Host Board" interface and a special connector for more power and IO to/from the "CPU card" in order to do things like support ISA, PCI, peripherals, and later PCI-X slots. Rather than having the extra complexity of the connectors, the high volume PC market folded all of this "onto the backplane" creating the modern motherboard. It might not be clear unless you know a bit about early computer backplanes like S-50/S-100, STD bus, STEbus, VME bus and the equivalent Passive ISA backplanes... by the 90s this is well underway and we already have motherboards that you could recognise as "a motherboard" and "backplanes" that are noticeably different, having evolutionarily diverged during the 80s under differing economic pressures.