cliff@ethos.UUCP (Cliff Elam) (06/26/87)
I am going to get a 72M Miniscribe drive to put in my 7300
(this 20M drive eats big weenie) and I am not decided on
it's installation method: get a case/ps/cable or buy
the bigger chassis from AT&T.
I'd love to hear/see some reccomendations from 7300 owners
who have made either conversion. In any case I need to know
how to get the cover off and what new cables I gotta buy.
cliff@fubar or for sure mailings try:
--
Cliff {ihnp4,mcnc}!ethos!cliff
Increase our bandwidth: Shrink headers, use abbrev's, BAN CUTE SHIT!ken@maxepr.UUCP (Ken Brassler) (06/26/87)
In article <1377@ethos.UUCP> cliff@ethos.UUCP (Cliff Elam) writes: >I am going to get a 72M Miniscribe drive to put in my 7300 >I'd love to hear/see some reccomendations from 7300 owners >who have made either conversion. In any case I need to know >how to get the cover off and what new cables I gotta buy. Following is an article I posted to the unix-pc net about 1 year ago which is a recap of what I did to add a ST4096 external drive to my 7300. I hope it will be helpful to the hordes of new 7300 owners. Assume that every disclaimer you have ever seen is appended to this article. If you decide to follow my advice, it's because you have considered all alternatives, and arrived at the same conclusions that I did. Installing an external hard disk on a PC 7300. CHOOSING A DISK The current hard disk driver on the 7300/3B1 is limited to 8 heads, 1024 cylinders. The ST4096 has 9 heads, 1024 cylinders, so you will lose 1 head, or 1/9 th of the maximum drive capacity. If you choose a disk with 4 heads and 2048 cylinders, (for instance, it probably doesn't exist), you will lose 1/2 of the drive capacity. Number of tracks = heads x cylinders. Each track has 17 sectors, each sector is 512 bytes. The 7300 reserves the last sector of each track as an alternate bad block, leaving 16 available sectors. The maximum hard disk capacity on a 7300 is then: 8 x 1024 x 16 x 512 = 67,108,864 bytes, however, since 1K = 1024 bytes, it's probably more correct to call it 65.5 MB. WHAT YOU NEED A hard disk, a cabinet, a power supply, two unshielded flat ribbon cables 4 or 5 feet long with a female connector on one end and a printed circuit edge connector on the other end. One cable is 20 conductor, the other 34. You might want to add male panel mounted connectors to the back of the external cabinet. INSTALLATION The hardest part is opening up the 7300 case. There are 4 screws, 2 in the back located on each side of the I/O connectors, and two on the top of the case below where the keyboard is stored. Look just in front of where the keyboard plugs in. Pry off the flat plastic insert to reveal the screw head. The front of the cover has 'lands' molded in which mate with holes in the metal baseplate. Slip a putty knife between the plastic and metal base and gently pry them apart. Lift the top cover straight up (including CRT) until it clears the base, then tilt it back and lay it on the table directly behind the computer. (It winds up resting on the back of the CRT) The cables are just long enough to do this. The metal plate you then see will tilt back on 2 rear hinges after removing 3 screws along the front. But first, you must remove 2 connectors. One is the power supply connector, about half way back on the right side, the other is the video connector, about half way back on the left side. Do not pull on the video connector wires. Reach in with a pair of needle nose pliers and grab the connector itself. Lift the plate, remove the current HD connectors and replace them with your new cables. It is easier to snake the cables through the back of the machine if you have not yet put the connectors on the other end. Route the cables out the back just a little left of center. You will pass over a sharp metal edge, so tape a piece of cardboard beneath the cables for abrasion protection. Note the polarity of the cables, and close the computer back up. You can also remove the internal disk at this time, or wait until the new disk is confirmed operational. Whatever you choose, run the diagnostic disk first, to park the heads. Many of the hard disks come preconfigured for an AT. This means that the disk selector switch (or jumper) will be set for drive #2. Change this to drive #1. Finish up the cabling and plug everything together. TRY IT OUT. Cross your fingers. Turn on the HD power supply and listen to the platters spool up and then the heads return to home. Insert the diagnostic floppy disk, and switch on the computer. When you see the menu, do not do what it says, instead enter 's4test'. (no qoutes) You will see the prompt: expert> Enter '2', for initialize hard disk, then answer the disk parameter questions. When it asks for # of sectors, use the default 17. Reserving one sector for bad blocks is done internally. The drive should format. If it doesn't, check that drive #1 was selected on the hard disk drive select switch, or check the polarity of your cables. If you are facing the computer and the hard disk, the leftmost wire at the motherboard connector should be the leftmost wire at the HD pc board edge connector. (This is true for the ST4096 I used, I suppose other disks could be different) When the formatting is complete, decline the surface test. Instead, when back at the 'expert>' prompt, choose '3', for enter bad blocks. (The wizards tell me that the factory test is much more revealing than the resident 7300 surface test.) Choose the 'cylinder, head, byte' format, and enter the information which is supplied on the bad block report taped to the side of the hard disk. The 'byte' information they want is the byte offset from start of track, labeled 'bytes/index' on my report. When finished, turn off the computer power to reset the machine. Insert floppy disk #2 and turn on the power. Continue with normal loading of foundation set. ------------------------------------------------------------------ List of materials Qty. Part Description Price Total 2 IDS20 Ribbon socket 1.00 2.00 1 IDE20 Ribbon edge card 2.25 2.25 1 IDM20 Ribbon header 5.50 5.50 2 IDS34 Ribbon socket 1.60 3.20 1 IDE34 Ribbon edge card 2.75 2.75 1 IDM34 Ribbon header 7.00 7.00 The above part numbers from JDR Microdevices, 110 Knowles Drive, Los Gatos, CA 95030 800-538-5000 (408) 866-6200. The cabinet I used was from QIC Research Inc., 753 Ames Ave, Milpitas, CA 95053. 800-843-0806, (408) 942-8088. It is simply called "External box". Price $99.00. (includes a quiet DC muffin fan and power supply) 5' 20 conductor ribbon 5' 34 conductor ribbon 1 Hard disk, ST506 interface or compatible ----------------------------------------------------------------------- -- Ken Brassler {ihnp4|qantel|pyramid|lll-crg}!ptsfa!maxepr!ken ....ethos!gladys!ptsfa!maame ame a
davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) (06/29/87)
In article <1377@ethos.UUCP> cliff@ethos.UUCP (Cliff Elam) writes: >I am going to get a 72M Miniscribe drive to put in my 7300 >(this 20M drive eats big weenie) and I am not decided on >it's installation method: get a case/ps/cable or buy >the bigger chassis from AT&T. I went to my local dealer and got a data cable from an AT clone. It's long enough to work and short enough to reduce chances of nois pickup. For power I got a "Y" connector and spliced *heavy* wire into one leg. This allows me to keep my 7300 unmodified, and still have what I need. I soldered in either #12 or #14 stranded wire. The 7300 power supply is not too powerful, and I would rather not have voltage drops. -- bill davidsen (wedu@ge-crd.arpa) {chinet | philabs | sesimo}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me