xerox 820造句

• Tallgrass first developed subsystems for the Xerox 820 computer, for an Alpha Microsystems computer, and was working on an Apple IIe version when IBM announced the PC in August 1981.
• Flipping the Xerox 820-II's console between 8 bit and 16 bit modes on a 820-II which was equipped with the optional 16-bit processor card was accomplished by a simple keyboard control command.
• Few corporate executives ever saw or used the system, and the sales teams, if they requested a " computer " to assist with their planning, would instead receive older, CP / M-based Xerox 820 or 820-II systems.
• 1 ) the Xerox 820 mainboard had built-in 8 " floppy disk I / O devices but no built-in 5.25 " floppy disk I / O devices nor hard disk I / O ( nor any expansion bay capabilities ), whereas
• Through the 1970s, Xerox showed no interest in the work done at PARC . When Xerox finally entered the PC market with the Xerox 820, they pointedly rejected the Alto design and opted instead for a very conventional model, a CP / M-based machine with the then-standard 80 by 24 character-only monitor and no mouse.
• Finally, the Xerox 820-II had a processor expansion capability, which optionally supported a 16-bit Intel 8086 processor card with its own 128 kiB or 256 kiB of RAM ( the 16-bit processor card did, however, employ the on-mainboard Z80A for " all " peripheral I / O operations, therefore the 8086 behaved more like a co-processor ).
• 2 ) the Xerox 820-II mainboard had no built-in disk I / O devices nor a built-in processor expansion capability ( these were expected and required to be on expansion bay cards; there were two different expansion bay connectors, one which accommodated one of several disk I / O boards, and one which accommodated a processor board the processor board was the taller of the two ).
• A simple modification to the Xerox 820-II's BIOS initialization code was developed to move the BIOS image up to the top of the 512 kiB RAM area, thereby giving the applications maximum contiguous RAM . Otherwise, the 512 kiB of the converted processor card was segmented into a lower 128 kiB segment, and an upper 384 kiB segment, but CP / M-86 was designed to handle such segmented RAM, so this BIOS modification was optional, although it was desirable.
• Unlike much later processors from Intel, and others, which offered " both " segmented " and " " flat " addressing, the 8086 ( and the 8088 ) offered " only " segmented addressing, with each segment being limited to 64 kiB . By effective utilization of the four available segment registers, Code, Data, Stack and Extra, the 512 kiB address space possible with the modified Xerox 820-II 8086 processor card could be very effectively managed, although in 64 kiB chunks.
• Xerox 820-II component parts were available from Xerox outlet stores at quite reasonable prices, and it was not uncommon to convert surplus ( but new ) 128 kiB 16-bit processor cards to 512 kiB by the substitution of sixteen 41256 DRAM chips for the card's usual sixteen 4164 DRAM chips ( both are 16-pin DIPs pin 1 is unused on a 4164 and becomes A8 on a 41256 ), plus the addition of two ICs ( one 74F02 and one 74F08, or two user-modified PALs ) for controlling the 41256's 9th address row and column ( not found on 4164s ), thereby achieving a four-times increase in RAM without the use of a " daughter " card ( which could only achieve a two-times increase in RAM ).