Jiggy -
Software coded for the original ("old") Pentium will work on the new MMX enhanced Pentium but at the same speed as the old Pentium, assuming the new and the old run at the same clock speed. As I noted in another reply, my bet is that the enhanced Pentium MMX will ship at very high clock rates, >= 200 MHZ.
The fact that the old software will run on the new Pentium MMX devices may seem trivial, or obvious, but I think it reflects a key strategy implemented by Intel since the days of the 8080. When they introduced the 8086/8088 in 1978/79, the 8086 was designed to execute 8080 instructions (after recompilation of course). Ever since then, any code written for the 8086/8088 can be run on all Intel x86 machines.
This was originally a detriment for Intel. The 8086 contained a lot of excess baggage to perform this, not the least of which was segmented addressing with 64 Kilobyte Segments. This hampered all software development for years, and still does as evidenced by "16 bit compatibility" that Windows 95 still incorporates, in order to run this old 16 bit software (Note in binary math: 2 raised to the 16'th power is 64 K = 65,536.). That is, the largest single block of code or data is limited to 65,536 bytes directly and the software must manipulate segemnt registers directly to point to code/data beyond these limits. This slows things down considerably.
In fact, the 386/486/Pentium/Pentium Pro are still segmented address machines, but the segemnt size is 2 to the 32nd power, since these are 32 bit machines, Thus, they can address 4,294,967,296 Bytes ( 4.2 GigaBytes). I believe that most software for the 386/486/Pentium just employ one segement (rather trivial) to make addressing strictly linear like most other "elegant" 32 bit processors. However, the segmented architecture with 2^32 addresses per segemnt, and thousands of possible segments, allows the potential for incredibly sophisticated software, but I'm not certain if any software or OS utilizes these "features". Maybe one day ......
With these large segments and very agressive speed improvements due to Intel's scaled process technology, most of the old baggage (i.e., software) moves along at very acceptable rates, even under Windows which places extraordinary demands on processor speed due to its message passsing architecture. But "that's a whole 'nuther story".
Paul |
