Jihad needs scientists
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From: Ken Smith on 10 Mar 2007 16:06 In article <ac547$45f316dd$49ecf63$21139(a)DIALUPUSA.NET>, nonsense(a)unsettled.com <nonsense(a)unsettled.com> wrote: >Ken Smith wrote: >> In article <esu74a$8qk_001(a)s861.apx1.sbo.ma.dialup.rcn.com>, >> <jmfbahciv(a)aol.com> wrote: > >massive snip > > >>>I was never aware that the purpose of IRGs was so a human could >>>edit directly to the tape. >> >> >> We are not talking about humans doing things we are talking about what >> computers could do. >> >> >>>Yes! THat is the only way to get a directory of the tape. >> >> >> Then as I have explained, the method works the checksum did not need to be >> wrong. > >BAH is right. No she is wrong. > >You run a checksum of the tape. > >You write the checksum to the tape. This isn't what she is doing. TAPE.DIR contains the list of files on the tape along with their checksums. It isn't the checksum of the whole tape. >The checksum of the tape has changed and is therefore now incorrect. >Every time you change the checksum data, the checksum changes. Not if you do as I suggested way back <--------- That way. To give you a quick run down on it, since you missed it: Here's what the TAPE.DIR file on the disk (ie: not yet put onto tape) looks like: *** begin ******** *Please ignore this line ZZZZ Directory of this tape with no errors FILENAME CHECKSUM TAPE.DIR 0000 FILE000 1234 FILE001 5678 ***** end ****** Now you make a checksum of this file and get a checksum of 1313. You go back and modifify the TAPE.DIR before you write it to read: *** begin ******** *Please ignore this line YWYW Directory of this tape with no errors FILENAME CHECKSUM TAPE.DIR 1313 FILE000 1234 FILE001 5678 ***** end ****** The change to the "ZZZ" exactly compensated the change to the "0000" leaving the checksum exactly as it was and thus still correct. This trick was already old when I was a mere lad. >There's no way around it, Did you just change your mind? -- -- kensmith(a)rahul.net forging knowledge
From: Ken Smith on 10 Mar 2007 16:15 In article <72ef1$45f31da7$4fe7333$21289(a)DIALUPUSA.NET>, nonsense(a)unsettled.com <nonsense(a)unsettled.com> wrote: >Ken Smith wrote: >> In article <b6a74$45f2f36e$4fe72af$20401(a)DIALUPUSA.NET>, >> nonsense(a)unsettled.com <nonsense(a)unsettled.com> wrote: >> >>>Ken Smith wrote: >>> >>>>In article <esu5o4$8ss_003(a)s861.apx1.sbo.ma.dialup.rcn.com>, >>>> <jmfbahciv(a)aol.com> wrote: >>>> >>>> >>>>>In article <esrr8b$n5i$2(a)blue.rahul.net>, >>>>> kensmith(a)green.rahul.net (Ken Smith) wrote: >>>> >>>>[....] >>>> >>>> >>>>>>>These used to be called private packs. The concept has existed since >>>>>>>the 60s. >>>>>> >>>>[....] >>>> >>>> >>>>>>The operator allocated them >>>>>>after you paid large amounts of money. >>>>> >>>>>That depended on the site. You seem to be talking from an IBM >>>>>operational POV. >>>> >>>> >>>>Yes, an IBM environment >>>> >>>> >>>> >>>>>Ours was designed differently. It was easy >>>>>to redirect any spooling to a pack reserved for that purpose. >>>>>Video downloads, etc. could be in a similar category. >>>> >>>> >>>>Who did the "reserved for that purpose"? That would be the point where >>>>money would be needed. >>>> >>>>[....] >>>> >>>> >>>>>>Where you evolve to depends a lot on where you start. In this case, there >>>>>>is a large factor from the seemingly unimportant choices made in the early >>>>>>days. >>>>> >>>>>Those weren't unimportant choices. They were deliberately made with >>>>>certain goals and non-goals in mind. No development was an >>>>>accident. >>>> >>>> >>>>Sure it was. In both hardware and software design there are often choices >>>>that look identical today but won't in the future. For a long time logic >>>>has run on 5V. The selection of 5V can be traced in part to the heater >>>>voltage on tubes. >>> >>>That's not true. Most of the vacuum tubes use(d) 6 volts and upwards. >> >> >> Yes, it is true. The heater voltage on many tubes was 6.3VAC. I'll leave >> the *sqrt(2) and the headroom numbers for you to go find. When you get >> done, you will see why 5V was the nearest round number. > > >6.3 * .707 = 4.45 making 4 volts the nearest round number. sqrt(2) != 0.707 I'll do it for you: 6.3 * sqrt(2) = 6.3*1.414 = 8.9V Low line condition = -10% ie: 0.9 times the above 8.9 * 0.9 = 8.0 The rectifier is a silicon diode: 8.0 - 0.7 = 7.3V The regulator was from before LDOs were invented. So lets use the LM78XX as an example design: http://www.fairchildsemi.com/pf/LM/LM7805.html says drop out voltage = 2.0 7.3 - 2.0 = 5.3 Round off 5V -- -- kensmith(a)rahul.net forging knowledge
From: Eeyore on 10 Mar 2007 16:27 "nonsense(a)unsettled.com" wrote: > Ken Smith wrote: > > > > Yes, it is true. The heater voltage on many tubes was 6.3VAC. I'll leave > > the *sqrt(2) and the headroom numbers for you to go find. When you get > > done, you will see why 5V was the nearest round number. > > 6.3 * .707 = 4.45 making 4 volts the nearest round number. How about the forward voltage drop for the rectifier ? Graham
From: MassiveProng on 10 Mar 2007 16:37 On Sat, 10 Mar 2007 21:27:41 +0000, Eeyore <rabbitsfriendsandrelations(a)hotmail.com> Gave us: > > >"nonsense(a)unsettled.com" wrote: > >> Ken Smith wrote: >> > >> > Yes, it is true. The heater voltage on many tubes was 6.3VAC. I'll leave >> > the *sqrt(2) and the headroom numbers for you to go find. When you get >> > done, you will see why 5V was the nearest round number. >> >> 6.3 * .707 = 4.45 making 4 volts the nearest round number. > >How about the forward voltage drop for the rectifier ? > Semiconductor diodes, yes. Do tube rectifiers have the same "forward drop"? I doubt it as a hot tube is very happy to pass electrons.
From: Ken Smith on 10 Mar 2007 16:43
In article <45F322CD.B05B27EE(a)hotmail.com>, Eeyore <rabbitsfriendsandrelations(a)hotmail.com> wrote: > > >"nonsense(a)unsettled.com" wrote: > >> Ken Smith wrote: >> > >> > Yes, it is true. The heater voltage on many tubes was 6.3VAC. I'll leave >> > the *sqrt(2) and the headroom numbers for you to go find. When you get >> > done, you will see why 5V was the nearest round number. >> >> 6.3 * .707 = 4.45 making 4 volts the nearest round number. > >How about the forward voltage drop for the rectifier ? Go look that way ^ / ! \ ! ! You will see where I spelled it all out. -- -- kensmith(a)rahul.net forging knowledge |