4 ms·

> “In fact it is known that DOS 2.0 could not be built on PCs at all, and was built on DEC mainframes.” Nitpick, but DEC never made a mainframe. Their products

by pavlov 2y ago

> “In fact it is known that DOS 2.0 could not be built on PCs at all, and was built on DEC mainframes.” Nitpick, but DEC never made a mainframe. Their products like the PDP-11 were considered minicomputers (even though the CPU was the size of a fridge) to distinguish them from IBM’s mainframes and medium sized computers.

p_l 2y ago
The PDP-11 was minicomputer, but PDP-10s were "minis" only formally, with VAX due to reasonable size and comparable performance coining the title "supermini" IIRC.
surgical_fire 2y ago
Nitpick, but as far as I remember, minicomputers are midrange computers. DEC PDP-11 would be in the same class as IBM AS/400, so while they were distinguished from mainframes, they were "medium sized computers". Assuming, of course, that those "medium sized computers" are the midrange.
- jasomill 2y ago
  This gets even more confusing when you consider that IBM released a number of mainframes smaller than many of their midrange systems, including both System/370 and System/390 systems implemented as PC expansion cards (ISA, MCA, and PCI). Ultimately, within IBM at least, "mainframe" ended up just referring to any computer that implemented the System/360 architecture or its descendants. Outside IBM, I've seen the term applied to just about any multiuser system accessed primarily through a terminal interface, including x86 servers running Linux, though typically by nontechnical users.
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retrac 2y ago
DEC was always finnicky about naming; the PDP series originally wasn't supposed to be called a computer because computers were thought of as much bigger than the products DEC sold, and customers in the 50s and 60s might be put off by a name they associated with multi-million dollar expenses. But the PDP-10 and VAX 9000 were basically mainframes. Million dollars or more. Whole large room with three phase power. Standard building AC might suffice but that was pushing the margin. And the faster clocked VAX 9000 was water cooled! That's not a minicomputer.
- mmooss 2y ago
  > But the PDP-10 and VAX 9000 were basically mainframes. Million dollars or more. Whole large room with three phase power. Standard building AC might suffice but that was pushing the margin. And the faster clocked VAX 9000 was water cooled! That's not a minicomputer. Why is that not a minicomputer. From our perspective it's a massive installation; from the perspective of the time, it was not necessarily.
  - varjag 2y ago
    Minicomputer at the time was considered a system that fits in a rack or three. Not something that requires a purpose built room with own mains, raised floor and AC.
  - deleted 2y ago
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  - somat 2y ago
    I am not exactly sure what makes a modern mainframe(same architecture as a historical mainframe I guess) but for historical machines I consider the wide machines(like the 36-bit pdp-10) mainframes, where minicomputers were usually narrower. 16 or 18 bit machines. Really there is no good formal definition, dividing computers into three groups(mainframe, minicomputer, microcomputer) based on how much you payed for it, is as good a mechanism for figuring this out as any other.
- brucehoult 2y ago
  My PC is water cooled. However the VAX 9000 wasn't. It was initially designed to be water cooled but during development they improved the air cooling enough that water cooling was never shipped. One VAX 9000 CPU did around 70k Dhrystones/sec, so 40 VAX MIPS (DMIPS as we call them now). A modern simple RISC 5-stage in-order CPU (e.g. Berkeley RISC-V Rocket) with decent branch prediction does 1.6 DMIPS/MHz, so will need 25 MHz to match the VAX 9000. However the December 2016 HiFive1 ran at 320 MHz, so would be around a dozen times faster than the VAX 9000 -- but without FPU or MMU. Today, a $5 Milk-V Duo running at 1 GHz (64 bit, and with MMU and FPU and vector unit) will be 40x faster than a VAX 9000. The VAX 9000 has a vector unit, capable of a peak 125 MFLOPS. The Duo's C906 VFMACC.VV instruction has 4 cycles latency, for two 64-bit multiply-adds or four 32-bit multiply-adds, so at 1 GHz that's 1 GFLOP double precision or 2 GFLOP single precision, 8x a VAX 9000. Don't even ask what a modern i9 or Ryzen can do!
mepian 2y ago
The PDP-10 was a mainframe: https://en.wikipedia.org/wiki/PDP-10#cite_note-1 https://en.wikipedia.org/wiki/PDP-10#cite_note-1
- deleted 2y ago
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Hilift 2y ago
It was probably a VAX 11/780. If you were cheap you purchased an 11/750. The 780 had a PDP-8 for a console processor. https://news.microsoft.com/features/the-engineers-engineer-computer-industry-luminaries-salute-dave-cutlers-five-decade-long-quest-for-quality/ https://news.microsoft.com/features/the-engineers-engineer-c...
- SulphurCrested 2y ago
  The console processor was an LSI-11, a PDP-11 on a chip. It hung off the inside of one of the cabinet doors. It was responsible for booting the 780 and also gave VMS access to its own 8″ floppy drive, which had a habit of overheating. The 750 was later technology, IIRC MOSFET. It also lacked the 780’s “compatibility mode”, which allowed VMS to run 16 bit RSX-11 executables by implementing the PDP-11 instruction set in addition to the 32 bit VAX one, and could boot without a console processor. If you didn’t need all the users on one machine, the 750 was cheaper per user.

by pavlov 2y ago

p_l 2y ago

The PDP-11 was minicomputer, but PDP-10s were "minis" only formally, with VAX due to reasonable size and comparable performance coining the title "supermini" IIRC.

surgical_fire 2y ago

Nitpick, but as far as I remember, minicomputers are midrange computers. DEC PDP-11 would be in the same class as IBM AS/400, so while they were distinguished from mainframes, they were "medium sized computers". Assuming, of course, that those "medium sized computers" are the midrange.

jasomill 2y ago
This gets even more confusing when you consider that IBM released a number of mainframes smaller than many of their midrange systems, including both System/370 and System/390 systems implemented as PC expansion cards (ISA, MCA, and PCI). Ultimately, within IBM at least, "mainframe" ended up just referring to any computer that implemented the System/360 architecture or its descendants. Outside IBM, I've seen the term applied to just about any multiuser system accessed primarily through a terminal interface, including x86 servers running Linux, though typically by nontechnical users.

deleted 2y ago

[deleted]

retrac 2y ago

DEC was always finnicky about naming; the PDP series originally wasn't supposed to be called a computer because computers were thought of as much bigger than the products DEC sold, and customers in the 50s and 60s might be put off by a name they associated with multi-million dollar expenses. But the PDP-10 and VAX 9000 were basically mainframes. Million dollars or more. Whole large room with three phase power. Standard building AC might suffice but that was pushing the margin. And the faster clocked VAX 9000 was water cooled! That's not a minicomputer.

mmooss 2y ago
> But the PDP-10 and VAX 9000 were basically mainframes. Million dollars or more. Whole large room with three phase power. Standard building AC might suffice but that was pushing the margin. And the faster clocked VAX 9000 was water cooled! That's not a minicomputer. Why is that not a minicomputer. From our perspective it's a massive installation; from the perspective of the time, it was not necessarily.
- varjag 2y ago
  Minicomputer at the time was considered a system that fits in a rack or three. Not something that requires a purpose built room with own mains, raised floor and AC.
- deleted 2y ago
  [deleted]
- deleted 2y ago
  [deleted]
- somat 2y ago
  I am not exactly sure what makes a modern mainframe(same architecture as a historical mainframe I guess) but for historical machines I consider the wide machines(like the 36-bit pdp-10) mainframes, where minicomputers were usually narrower. 16 or 18 bit machines. Really there is no good formal definition, dividing computers into three groups(mainframe, minicomputer, microcomputer) based on how much you payed for it, is as good a mechanism for figuring this out as any other.
brucehoult 2y ago
My PC is water cooled. However the VAX 9000 wasn't. It was initially designed to be water cooled but during development they improved the air cooling enough that water cooling was never shipped. One VAX 9000 CPU did around 70k Dhrystones/sec, so 40 VAX MIPS (DMIPS as we call them now). A modern simple RISC 5-stage in-order CPU (e.g. Berkeley RISC-V Rocket) with decent branch prediction does 1.6 DMIPS/MHz, so will need 25 MHz to match the VAX 9000. However the December 2016 HiFive1 ran at 320 MHz, so would be around a dozen times faster than the VAX 9000 -- but without FPU or MMU. Today, a $5 Milk-V Duo running at 1 GHz (64 bit, and with MMU and FPU and vector unit) will be 40x faster than a VAX 9000. The VAX 9000 has a vector unit, capable of a peak 125 MFLOPS. The Duo's C906 VFMACC.VV instruction has 4 cycles latency, for two 64-bit multiply-adds or four 32-bit multiply-adds, so at 1 GHz that's 1 GFLOP double precision or 2 GFLOP single precision, 8x a VAX 9000. Don't even ask what a modern i9 or Ryzen can do!

mepian 2y ago

The PDP-10 was a mainframe: https://en.wikipedia.org/wiki/PDP-10#cite_note-1 https://en.wikipedia.org/wiki/PDP-10#cite_note-1

deleted 2y ago
[deleted]

Hilift 2y ago

It was probably a VAX 11/780. If you were cheap you purchased an 11/750. The 780 had a PDP-8 for a console processor. https://news.microsoft.com/features/the-engineers-engineer-computer-industry-luminaries-salute-dave-cutlers-five-decade-long-quest-for-quality/ https://news.microsoft.com/features/the-engineers-engineer-c...

SulphurCrested 2y ago
The console processor was an LSI-11, a PDP-11 on a chip. It hung off the inside of one of the cabinet doors. It was responsible for booting the 780 and also gave VMS access to its own 8″ floppy drive, which had a habit of overheating. The 750 was later technology, IIRC MOSFET. It also lacked the 780’s “compatibility mode”, which allowed VMS to run 16 bit RSX-11 executables by implementing the PDP-11 instruction set in addition to the 32 bit VAX one, and could boot without a console processor. If you didn’t need all the users on one machine, the 750 was cheaper per user.