gmark@ihlpf.ATT.COM (Stewart) (03/04/88)
I've been trying to determine the difference between the 7300 and the 3B1 and what actually is added by the swap of motherboards and plastic hoods that are included in the conversion kit. So far I've been led to believe that the following is correct, and would like anyone out there to confirm this: The conversion kit consists of, of course, a new motherboard, a new "high-top" hood, and a larger and faster hard disk. It appears that the only reason for for this is that the installers would have a devil of a time adding the additional 36 4256 RAM chips to the multi-layer board, especially on site. I have found no indication in any of the documentation (so far) that there is any difference in speed between the 36 chips on the existing board and the 72 chips on the new one. I have not been able to see a difference on the schematic, so I suspect there are jumpers for this (I had a 7300 apart for only a few minutes). As one can see from the specs, the replacement drives are considerably faster than those installed in the 7300s. I see no difference in clock speeds, but I've heard that, although the power supply is the same, the larger HD is connected via a direct cable to the supply rather than via the motherboard. The cost of the conversion kit, though seeming high, is pretty much in keeping with the expected AT&T prices for the included components. Note that many differences that people may see between machines MAY be due to their having worked on different revisions, and not due to the machines being 7300s nd 3B1s. ** SO, you expert UNIX-PC hardware hackers out there -- if I were to swap the HD, add extra RAM (maybe just an expansion board - I seem to remember seeing that the 1/2 Meg can be populated with 2Meg), swap the hood, I would then have a 3B1, RIGHT? G. Mark Stewart ATT-BTL Naperville ix1g266 979-0914 ixlpq!gms
ken@maxepr.UUCP (Ken Brassler) (03/05/88)
In article <3898@ihlpf.ATT.COM> gmark@ihlpf.ATT.COM (Stewart) writes: >** SO, you expert UNIX-PC hardware hackers out there -- if I were >to swap the HD, add extra RAM (maybe just an expansion board - >I seem to remember seeing that the 1/2 Meg can be populated with >2Meg), swap the hood, I would then have a 3B1, RIGHT? The Unixpc reference manual, which was probably written by Convergent Tech, makes no distinction between a 7300 and a 3b1. As a matter of fact, the 7300/3b1 terminology is never mentioned. Instead, it describes a single computer that can have from 1/2 to 2 meg of ram, and 10 to 67 meg of hard disk. 3b1, it seems, is just AT&T marketing terminology. Others will no doubt tell you of the problems you may encounter trying to upgrade the motherboard ram to 2 meg. But I think you should consider mounting your new hard disk in an external cabinet, with it's own power supply. Here's why; 1. The cabinet & power supply will cost around $100, about the same as a new 3b1 cover (if you can still get it). 2. You will remove considerable load from the internal supply, which seems to be a weak spot in the machine. 3. You can use your existing disk as a quick change, standby disk, in the event of a crash. 4. If you need lots of disk space, you can buy several disks. Just shutdown, plug in a new disk, and reboot. 5. It's quieter with the disks located remotely. I put a small set of shelves behind and beneath my desk. It holds my disks and external modem. Makes a nice installation. Something to think of, anyway... -- Ken Brassler {ihnp4|qantel|pyramid|lll-crg}!pacbell!maxepr!ken
guy@ihuxy.ATT.COM (Berentsen) (03/08/88)
In article <495@maxepr.UUCP>, ken@maxepr.UUCP (Ken Brassler) writes: ... > The Unixpc reference manual, which was probably written by > Convergent Tech, makes no distinction between a 7300 and a 3b1. As a > matter of fact, the 7300/3b1 terminology is never mentioned. > Instead, it describes a single computer that can have from 1/2 to 2 > meg of ram, and 10 to 67 meg of hard disk. 3b1, it seems, is just > AT&T marketing terminology. 2 Meg on the mother board is the key distinction between 7300 & 3b1 1.) Rumor has it that memory on the mother board is faster (1 less wait state). 2.) With 2 meg on the mother board the system is expandable to 4 meg. 3.) This is the only feature of a 3b1 that is difficult/dangerous to install yourself.
ebh@argon.UUCP (Ed Horch) (03/08/88)
Speaking of RAM upgrades... I purchased two megs of Samsung 150ns DRAM, figuring on putting one in the other half of the motherboard (I have 1meg installed), and the other meg into the Combo board. Well, I put the RAM in the Combo board, and the diagnostics gave all sorts of terible complaints. Of course, since the diagnostics aren't documented beyond pass/fail (grr), I couldn't tell which specific parts were failing. But, when I had the RAMs tested, they all passed! Craig Votava told me: >A buddy of mine said that different memory chips offer different resistances >when current is put through them. The resistor packs on the board are there >to "even" the resistance out to a known value, so the packs that are there >are designed for the type of memory that the designer used. Sometimes, in >order to use chips that have a different resistance than what was designed >for, the resistor packs need to be changed. Anyone have any more info on this? I'd also be deeply indebted to anyone who could tell me more about reading the diagnostic outputs. (Oh yes, and the generic "add me to the list" to anyone who has succesfully added a second hard disk, or 1.2Mb floppy and wants to brag about it.) I've just about given up on the idea of adding the other meg to the motherboard. I just don't feel comfortable doing all that soldering on a board that will cost me as much to replace if/when I screw it up, as the whole machine cost when I bought it. I'll use the other meg in another machine, probably the Amiga I plan on buying pretty soon. Back to the original subject line: I know the complete 7300 -> 3B1 conversion kit is hideously expensive, but does anybody have pricing info for just the enclosure upgrade, i.e. the top cover, pan cover, video cable, etc.? I'd sure like to get my Miniscribe 6085 into the box. (BTW, for those of you considering this drive, I highly recommend it. It has run flawlessly 24 hours a day since November, through many nasty power problems. [110V? Yeah right, maybe on *average!]) My only complaint is that head movement's a little noisy. And yes, you do have to use the cable directly off the power supply. I tried using the cable off the motherboard and it didn't work. Oh, and one last little hint for those of you running full netnews on your 3B1: The news software keeps history information around for as long as the oldest article. If you don't use the -I option of expire, this will result in several weeks' worth of history info being kept around due to the long Expires: dates in comp.mail.maps postings. The 2Mb of history info is only a minor annoyance in terms of disk space, but it really slows down rnews processes, increasing the time by a factor of three over having three days' worth of history. What I use is a little shell script that a) does a general 3-day expire without the -I option, b) polls my feed sites for news, c) runs uuhosts -unbatch and pathalias to update the paths file, and d) does a one-day expire of comp.mail.maps *with* the -I option. I'd normally use a zero-day expire, but I want to keep the last day's input around in case something breaks. If there's sufficient interest, I can post this to unix-pc.sources. (I'm currently working on a mod to this script that handles failed polls better.) Well, we know that the 7300/3B1 has been discontinued :-(, but what's the status of the version Convergent markets? Is this still a Real Product, or are they just supplying parts for 7300/3B1's (as their agreement with AT&T says they will for a few more years)? -Ed Horch argon!ebh Some day, my Trailblazer will come...