Forum Rules and Etiquette

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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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Rule 2: Stay close to the original topic being discussed
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To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
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Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
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Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.

Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.

New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.

Other suggestions
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(Open Source) LLFormat Utility

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    (Open Source) LLFormat Utility

    In light of my numerous troubles with MFM drives, I feel like I need to be able to analyze what MFM formatting software is doing "under the hood" to avoid future woes. This includes what commands the software was sending to the BIOS or controller before formatting, how hard drive parameters were auto-detected, etc. A simple error code was not enough- and still isn't enough- for me to figure out exactly why my MFM/RLL controllers are so finicky depending on the computer. It would also help immensely to not have to go through DEBUG routines and restart the machine everytime! .

    I didn't see any open source versions (understandable, since it has a very specific use-case)- so I made my own! Well, right now I have the skeleton of a full program, and a proof-of-concept formatter that works on a single IBM drive type (Type 8 ). I have enclosed the source for those interested, and will add to it as I have time. I originally intended to do a BIOS-compatible version and a Xebec-compatible-detailed version (talk to the controller directly), but I think I may just combine the functionality into one program. I would appreciate any feedback anyone has to make the LLFormatting process less painful too .

    Again, this is proof-of-concept, and it only works on Type 8 or comparable (733 cyls, 5 heads, 17 sectors/track) drives. My comments are out of date (the attached source creates the EXE with which I successfully tested a real MFM drive), and there are instructions which do nothing meaningful other than add heat to the room. The progress indicator doesn't even count up in decimal, but in hex (I'll get to it)! But it does work, and the source code be modified to work on any MFM drive type with moderate effort. At this point, this program does not do a surface scan after formatting (if anyone can suggest good MFM test patterns beside FFFF and 0000, I'm all ears), and interleave is ignored (seems to be standard to ignore for AT controllers). I have NOT tested it on an 8-bit controller yet.

    One thing I find interesting is that in my initial test, I had CH and CL swapped from their correct positions when calling int 13h, subfunction 5...
    ;Perform format- registers ready
    mov ah, 05h
    int 13h
    Normally, CL holds the top 2 bits of the cylinder number and CH holds the bottom 8 bits. When this is reversed (which was necessary to print the hex value of the cylinder to the screen), this means that cylinders 00 to whatever got reformatted a significant number of times (I figured this out when I noticed significant seek delays between moving from cylinder 00 to 64 ). When I rebooted the machine during these tests, I got a fake "Track 0 bad" error from my BIOS- it just said "Primary Master Hard Disk Fail", but I can tell that it's related since the problem went away when I made sure CL and CH held the correct data.
    ;SI- copy of AX
    ;DI- copy of DX
    ;BP- copy of CX
    ;Print current track
    dosstr chs_str
    mov dx, si
    mov ax, di
    ;Perform format- registers ready
    mov bp, cx
    mov ax, cx
    xchg ah, al
    mov cl, 6
    shl al, cl
    mov cx, ax
    mov dx, si ;Restore DX
    mov ax, di ;Restore old AX
    mov ah, 05h
    int 13h
    mov cx, bp ;Restore CX
    SpeedStor also claimed Track 0 and others were bad when I performed media analysis.

    My question is: Why would a track format failure occur after repeated LLFormatting? I figured the disk would just write the same data structures repeatedly to cylinders 0 to whatever, so I'm not exactly sure I understand why repeated formatting would result in garbage tracks or unreadable data.
    Attached Files
    Looking for: Needham's Electronics PB-10 Microcontroller Adapter (looking for one since early 2012!).

    This is exciting. I have been doing some light study on how I may approach my initial HD care as my equipment arrives over the next week.
    I'm sure i;ll be trying this out after I get some re-experience with conventional software utilities from the era of my PC.
    Wanted: Sony CDU-535 or CDU6250 CD-ROM Drive (Caddy drive) for 8-bit Sony Interface Card
    sigpic <-- This is me using my IBM PC 5150 over Ethernet TCP/IP network with assignable drive letters