doug@terak.UUCP (Doug Pardee) (04/25/85)
Are my eyes deceiving me? Is someone really claiming that the reason that computing the Ackerman function in C on a VAX 11/750 takes 3.3 times as long as doing it in assembler on a Z-80A is because a VAX is just plain slower than a Timex/Sinclair?? > This, of course, presumes that the VAX is basically faster than a Z-80A > for short integer arithmetic. Why not compare apples to apples ? Other comments I've gotten by mail indicate that some folks also question the VAX's "call" & "return" speed compared with a TS-1000. If a VAX can't do integer arithmetic nearly as fast as a TS-1000, and a VAX can't do branching nearly as fast as a TS-1000, then why should one buy a VAX for 1000 times the price of a TS-1000?? (Other than because you can't get TS-1000's any more :-) -- Doug Pardee -- Terak Corp. -- !{hao,ihnp4,decvax}!noao!terak!doug
sid@linus.UUCP (Sid Stuart) (04/30/85)
>Other comments I've gotten by mail indicate that some folks also >question the VAX's "call" & "return" speed compared with a TS-1000. Doug, I have seen benchmarks that show a Motorola 68010 running at 10 megahertz doing ackerman's function at about twice the speed of a 780. Programs on both machines were written in C. I would still prefer to have a 780 over a 68010 or even a Z80 if all other things (cost) were equal. I do not believe ackerman's function to be a reasonable benchmark for testing anything other than timing on a jump to a subroutine. sid stuart
mat@amdahl.UUCP (Mike Taylor) (05/01/85)
> Are my eyes deceiving me? Is someone really claiming that the reason > that computing the Ackerman function in C on a VAX 11/750 takes 3.3 > times as long as doing it in assembler on a Z-80A is because a VAX is > just plain slower than a Timex/Sinclair?? > > > This, of course, presumes that the VAX is basically faster than a Z-80A > > for short integer arithmetic. Why not compare apples to apples ? > > Other comments I've gotten by mail indicate that some folks also > question the VAX's "call" & "return" speed compared with a TS-1000. > > If a VAX can't do integer arithmetic nearly as fast as a TS-1000, and > a VAX can't do branching nearly as fast as a TS-1000, then why should > one buy a VAX for 1000 times the price of a TS-1000?? (Other than > because you can't get TS-1000's any more :-) > -- > Doug Pardee -- Terak Corp. -- !{hao,ihnp4,decvax}!noao!terak!doug A VAX11/780, a "big brother" of the VAX11/750, has a cycle time of 200 ns. That is, a 5 MHz. clock in microprocessor terms. Simple things, like for example adding two registers, probably take one cycle on both the Z80A and the VAX. Therefore, for at least some trivial applications, the Z80A and the VAX are comparable. A VAX11/750 is slower than a VAX11/780 (I believe). If this is due to reduced clock rate for example, then it is conceivable that some operations are faster on the Z80A than on the VAX. I merely point out that the performance of the two machines depends on the application, and this uncertainty weakens the argument comparing the languages. An apples-to-apples comparison would be more convincing. As to why one should buy a VAX, I'm sure I don't know. I've never bought one, myself. -- Mike Taylor ...!{ihnp4,hplabs,amd,sun}!amdahl!mat [ This may not reflect my opinion, let alone anyone else's. ]
mann@LaBrea.ARPA (05/01/85)
> Simple > things, like for example adding two registers, probably take one cycle > on both the Z80A and the VAX. Sorry. Adding two (8-bit) registers takes 4 cycles on the Z-80A. In fact, none of the Z-80 instructions takes less than 4 cycles -- not even a NOP. This is why a 1 MHz 6502 can be comparable in speed to a 4 MHz Z-80. --Tim