ln63fkn@sdcc7.UUCP (Paul van de Graaf) (11/27/85)
A recent issue of "Electronics" mentions the 68070, an enhancement of the 68000 which includes, among other things, an on-chip MMU. It is a joint effort of Signetics and some other company whose name escapes me at the moment. Does anyone know if this chip is plug compatible with the 68000? Also, does it use any of the microcode from the 68K? I vaguely recall Signetics is a second-source for the 68K, therfore they would have a license on the technology. Does this allow them to manufacture enhanced versions of the chip which compete directly with Motorola? The chip sounds like an attractive way to add an MMU to a Mac/Amiga/Atari ST. I'm not sure if the chip has restartable instructions like the 68010, but I should hope so. Why bother to have an MMU if you can't handle virtual memory? I'd appreciate any info I could get. Thanks... Paul van de Graaf sdcsvax!sdcc7!ln63fkn U. C. San Diego
bjorn@alberta.UUCP (Bjorn R. Bjornsson) (11/30/85)
Paul van de Graaf (ln63fkn@sdcc7.UUCP) writes: > A recent issue of "Electronics" mentions the 68070, an enhancement of the 68000 > which includes, among other things, an on-chip MMU. It is a joint effort of > Signetics and some other company whose name escapes me at the moment. The other company is Philips, Signetics parent. > ................................................................ Does > anyone know if this chip is plug compatible with the 68000? Also, does it use > any of the microcode from the 68K? Don't know about plug compatibility, but there is almost no way the microcode could be the same, for according to "Electronic Design, Oct 31, '85" the 68k has 3 24 bit accumulators (read ALUs, at least one of which is in the address path), but the 68070 has 1 32 bit accumulator. Identical microcode is therefore out of the question (unless the 68k was programmed by 100 monkeys with bitmapped workstations, of course). > .......................................... I vaguely recall Signetics is a > second-source for the 68K, therfore they would have a license on the technology. > Does this allow them to manufacture enhanced versions of the chip which compete > directly with Motorola? Philips/Signetics is real heavy into 68k products/support chips. > The chip sounds like an attractive way to add an MMU to a Mac/Amiga/Atari ST. > I'm not sure if the chip has restartable instructions like the 68010, but I > should hope so. Why bother to have an MMU if you can't handle virtual memory? > I'd appreciate any info I could get. Thanks... The MMU can be configured with: 8 segments of 2Mbytes each or 128 segments of 128Kbytes each. I have no idea whether an instruction can be restarted/continued after an MMU abort. Who knows, maybe this "MMU" does'nt even relocate. Not the ideal MMU, but certainly better than nothing. If the operating 'monitors' of mac/atari-st/amiga are careful about running in supervisor mode and make sure that user processes run in user mode, then you could presumably protected said monitor program with a few instructions. Benefits? You don't have to boot and you won't loose your disk when your application dies. Other features: 2 16 bit timers, 2 DMA channels, 2 serial port, programmable interrupts, etc. Bjorn R. Bjornsson ihnp4!alberta!bjorn