31479Re: [midatlanticretro] VAX 780 vs. 750
- Jul 1, 2013On 07/01/2013 02:41 PM, David Riley wrote:
> The 11/750 was a smaller, slower, cost-reduced version of the 11/780. TheThe 11/730's implementation of the VAX instruction set is more
> 11/730 (even later), was a smaller, even slower, further cost-reduced version
> of the same. My recollection is that most of the size and cost reduction was
> accomplished by using more highly integrated gate arrays to replace discrete
> TTL logic chips (which, at the time, were faster than the gate arrays).
> I believe the 11/730 was small enough to be easily rack-mountable, while the
> 11/750 occupies most of a short cabinet. I could be misremembering, though;
> I've never actually seen any in the flesh (part of why I'm excited for the
heavily based in microcode than that of the 11/750, making it much
smaller and much slower. Basically fewer and fewer functions
implemented in hardware, more and more functions implemented in microcode.
The 11/730 CPU is built from Am2901 bit-slice chips. The control
store (where microcode lives) is actually RAM, so when the 11/730 is
powered up, it doesn't speak the VAX instruction set. Microcode is
loaded from a TU58 tape cartridge into the control store by an
8085-based service processor within the machine.
Most 11/730 CPUs are in BA11-K style chassis, VERY compact by VAX
standards of the day. Standard 19" rackmount.
The VAX-11/725 is an 11/730 repackaged into a roll-around deskside
chassis. The VAX-11/751 is a repackaged 11/750 that can be mounted in a
standard 19" rack. The 751 was targeted at embedded and OEM applications.
Dave McGuire, AK4HZ
New Kensington, PA
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