TUHS

tuhs@tuhs.org

34 participants
6420 discussions

by Norman Wilson

Dave Horsfall: Jon von Neumann was born in 1903; without him, we probably wouldn't have had computers at all (but we could've had a Wintel version, I suppose, wherein everything is controlled by BB). ==== On this day in Australia, but not yet in North America or Europe. Or, as Warren would probably prefer, it was 2015 in England, but still only 1903 in Australia. Such was the great difference in time twixt these two great nations. Australia, Australia, we love you from the heart, the liver, the kidneys, and the giblets, and every other part! Norman Wilson Toronto ON

9 years, 1 month

v6 RK05 bootloader question

by Will Senn

All, I'm trying to understand the RK bootloader code that is found in "Setting up Unix - Sixth Edition". My question is related to RKBA, RK's bus address buffer. Is the bus address the same as memory address? If so, the code makes sense, if not, I appreciate y'alls help. Here's what I have so far: RK05 01 012700 MOV 177414,R0 ; Move RKDB into R0 02 177414 ; RKDB Address 03 005040 CLR -(R0) ; Decrement R0 and clear the contents of RKDA 04 005040 CLR -(R0) ; Decrement R0 and clear the contents of RKBA 05 010040 MOV R0,-(R0) ; Move the contents of R0(RKBA) into decremented R0(RKWC) 06 012740 MOV 5,-(R0) ; Decrement R0 and move 5 into RKCS 07 000005 ; Read and go 08 105710 WAIT: TSTB (R0) ; Test the lower byte of RKCS 09 002376 BGE WAIT ; When bit 7 becomes 1, the read is done 10 005007 CLR PC ; Set PC 000000, the start of the bytes read RKDB - RK data buffer register This register is a general data register and it only used by the code above to initialize R0 so that subsequent RK addresses can be found by simply decrementing R0. RKDA - RK disk address register This register determines the starting disk address of the read operation and is cleared by the code. RKBA - RK current bus address register This register contains the bus address to or from which data will be transferred. Is this the same as memory address? RKWC - RK word count register Two's complement of the number of words to be transferred. RKCS - RK control status register This is the register that controls the device and provides the device status to the program Lines 1-2 The execution of the boot loader code moves the address of RKDB into R0 to initialize the register so that it can be used to obtain the other RK buffer addresses as they are needed. Line 3 The RKDA buffer is cleared, setting the disk address to 0. Line 4 The RKBA buffer is cleared, setting the bus address to 0. Line 5 The value in R0 is transferred into the RKWC buffer. RKBA or 177410, the value in R0, is a convenient number to use for the read operation because it is big enough to cause the program to read in a block of data. The number is in two's complement and represents -370. This tells the disk controller that 370 words (540 bytes) will be transferred. Lines 6-7 The value 5 is placed into RKCS, this value represents a read operation and go. Lines 8-9 The lower byte of RKCS is tested and when it is greater than or equal to zero (not negative), it loops, waiting until the value is negative, that is until bit 7 becomes 1, which indicates Control Ready (RDY) and done. Line 10 PC is set to 00000 and execution of the bytes read from the disk begins at location 00000.

9 years, 1 month

(no subject)

by Doug McIlroy

9 years, 1 month

(no subject)

by Doug McIlroy

9 years, 1 month

Re: [TUHS] Etymology of shell

by jnc＠mercury.lcs.mit.edu

> From: John Cowan > Rather than starting another process, the Multics shell mapped the > executable program the user requested into its own space .. then jumped > into it. The equivalent of exit() simply jumped back to the shell code. This is from memory, so apply the proverbial grain, but ISTR that the original concept for the Multics shell was just like that for Unix - i.e. each command would be a separte child process. This was given up when Multics processes turned out to be so computationally expensive, and they went to commands being subroutines that were dynamically linked in (very easy with Multics, where dynamic linking was a fundamental system capability) and called from the shell. Noel

9 years, 1 month

Etymology of shell

by Warren Toomey

So what is the etymology of "shell", then? I see that Multics has a shell. Was the CTSS user interface also called a shell? Cheers, Warren -- Sent from my Android phone with K-9 Mail. Please excuse my brevity.

9 years, 1 month

Etymology of "shell"?

by Warren Toomey

So what is the etymology of the word "shell"? I see that Multics has a shell. What the user interface in CTSS also called a shell? Cheers, Warren

9 years, 1 month

Mirror of Mike Mahoney's oral history of Unix

by Warren Toomey

All, Doug McIlroy sent me an e-mail about the late Mike Mahoney's project to create an oral history of Unix. His documents are at http://www.princeton.edu/~hos/Mahoney/unixhistory I've taken the liberty to mirror them into the Unix Archive and they are now also at http://minnie.tuhs.org/Archive/Documentation/OralHistory/ Cheers, Warren

9 years, 1 month

Re: [TUHS] etymology of cron

by norman＠oclsc.org

John Cowan: Wikipedia is by nature a *summary of the published literature*. If you want to get some folklore, like what "cron" stands for, into Wikipedia, then publish a folklore article in a journal, book, or similar reputable publication. Random uncontrolled mailing lists simply do not count. ====== That sounds fair enough on the surface. But if you follow the references cited to support the cron acronyms, you find that random unsupported assertions in conference papers do count. That's not a lot better. I'd like to see a published, citable reference for the true origin of `cron'. Even better, better published material for a lot of the charming minutiae of the early days of UNIX. (Anyone feel up to interviewing Doug and Ken and Brian and whoever else is left, and writing it up for publication in ;login:?) But I'd be satisfied if we could somehow stamp out the use of spurious references to support spurious claims. If I had the time and energy I'd look into how to challenge the cron acronyms on those grounds. Any volunteers? Norman Wilson Toronto ON

9 years, 1 month

Re: [TUHS] Does anybody recall how the TU10 bootstrap code actually operates?

by jnc＠mercury.lcs.mit.edu

> From: Will Senn > 000777 HALT That's actually "BR ."; the difference is important, since the CPU (IIRC) doesn't honour DMA requests when it is halted, and DMA needs to be working for the controller to read that first block (a secondary tape bootstrap) into memory. > This seems like gobbledegook to me. :-) > It moves the MTCMA (Magtape Current Memory Address) into R0, then it > moves the MTCMA into the MTBRC (Magtape Byte Record Count) "The address of the MTCMA into", etc. Looking quickly at the programming spec for the TM11 controllers, it wants a negative of the byte count to transfer in this register; the address of the MTCMA just happens to also be a large enough negative number to be usable as the (negative) size of the transfer request. (The first record is probably shorter than that, but that doesn't matter.) Note that this code could probably also have been written: MOV #172524, R0 MOV R0,@R0 and been equally functional. > then it moves 60003 into the MTC (Magtape control register), which > causes a read operation with 800BPI 9 Channel density. I'm too lazy to look at the programming spec for the details, but that sounds right. > Am I misinterpreting the byte codes or is this some idiosyncratic way to > get the Magnetic tape to rewind or something (the TM11 has a control > function to rewind, so it seems unlikely that this is the case No, it's just the shortest possible program to read the first block off the tape. It depends on i) the operator having manually set the tape to the right point (the start of the tape), so that it's the first block that gets read, and ii) the fact that the reset performed by hitting the 'Start' key on the CPU clears the TM11 registers, including the Current Memory Address register, so the block that's read is read into memory location zero. Hence the direction to 'once the tape has stopped moving, re-start the CPU at 0'. Noel

9 years, 1 month

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