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View Full Version : Altair, IMSAI, which is better?



Floppies_only
May 30th, 2008, 06:40 PM
Gang,

Title says it all. Everybody is hereby invited to spout off about which S-100 computer is their favorite. Hell, it doesn't even have to be one of those. Any S-100 computer that you like, and why is what's being asked for.

Sean

Dwight Elvey
May 31st, 2008, 07:25 AM
Hi
The IMSAI design is a little more refined but both work well enough.
Neither work particularly well without added bus terminators.
I have an IMSAI my self. It works well enough except it does
have issues when going across the 32K boundary. This is
most likely cross talk someplace in the system.
From a schematic point of view, they are almost identical.
Still, I prefer the IMSAI front panel. One doesn't develope
blisters entering large programs.
Dwight

MikeS
May 31st, 2008, 07:32 AM
Cromemco.

Serious systems; excellent hardware, good software, documentation & support, and I happen to have some ;-)

No blinkenlights front panels though ;-(

m

Floppies_only
May 31st, 2008, 07:00 PM
Cromemco.

Serious systems; excellent hardware, good software, documentation & support, and I happen to have some ;-)

No blinkenlights front panels though ;-(

m

I saw a picture of the Cromemco Z-1, and it looked like it had the exact same flashing lights as the IMSAI 8080 does.

I'd love to have it for it's twice as fast 4 MHz CPU, but in reality, it looks like it would be very hard to get software for either machine.

Sean

MikeS
May 31st, 2008, 09:46 PM
Oh, you guys *are* sharp!

Yes indeed; Cromemco started out as a couple of guys making S-100 video cards (although the bus wasn't called S100 then; as a matter of fact, Cromemco were largely responsible for the S-100 name). Then they developed a few other cards and decided to sell a system, using the IMSAI box and calling it the Z-1; after that they used their own chassis (and no more blinkenlights and toggle switches, alas).

Lots of software around for Cromemcos, assuming a standard FDC; although they sold their own CP/M workalike, CDOS, they will run most of the older CP/M software. There are also many languages, i.e. Fortran, Cobol etc. (and several flavours of BASIC of course). With an extra 64K you could also run their Z80 version of sort-of UNIX, which also included a CDOS (CP/M) simulator. There's also a pretty complete set of manuals, tech notes etc. on various web sites.

m

Floppies_only
June 1st, 2008, 01:09 PM
Oh, you guys *are* sharp!

Yes indeed; Cromemco started out as a couple of guys making S-100 video cards (although the bus wasn't called S100 then; as a matter of fact, Cromemco were largely responsible for the S-100 name). Then they developed a few other cards and decided to sell a system, using the IMSAI box and calling it the Z-1; after that they used their own chassis (and no more blinkenlights and toggle switches, alas).

Lots of software around for Cromemcos, assuming a standard FDC; although they sold their own CP/M workalike, CDOS, they will run most of the older CP/M software.

How do you tell if a piece of software will run on a particular system? eBay sellers are notorious for not having the manual and for basically knowing jack s**t about what they are selling.

Could you use the Z-1 with minifloppies? (5 1/4")

Sean

MikeS
June 1st, 2008, 02:34 PM
Well, in *broad* terms, if the software is written for CP/M and the system is running CP/M properly, there's enough memory, and the versions are compatible, then the software should run. But even though CP/M presents a more or less standard API, if you're doing anything on the screen or terminal other than line-by-line text, or you're running communication software, etc. then you'll have to do some configuring since screen control codes vary from device to device, and apps like comm etc. usually have to bypass CP/M and deal with differing hardware directly for speed.

I don't know whether 5 1/4 disks and controllers were available in the Z-1 days, or what controller was in it; AFAIK Cromemco's controllers have always been dual-mode from the 4FDC onward.

m

Floppies_only
June 1st, 2008, 04:21 PM
I don't know whether 5 1/4 disks and controllers were available in the Z-1 days, or what controller was in it; AFAIK Cromemco's controllers have always been dual-mode from the 4FDC onward.

m

Yesterday I Xeroxed two pages of an old Byte magazine. The title of the article I was after is "Low Priced Disk System for Altair/IMSAIs". It tells of the North Star Micro-Disk System, a compact version of the standard Shugart floppy with the SA-400 minifloppy drive. The system came with a DOS disk, which makes me think that it's a dead end because it's not CP/M.

What I want to do with an S-100 computer (after I strech my mind by doing what it takes to get it going) is balance my checkbook every day and write USENET posts and then transfer them to a modern computer to send what I've written. I'd like to have a system with minifloppy drives because I can buy 5 1/4" disks from Athana, brand new.

I am in this for the long haul. It's good that you can use a PC as your floppy drive, but even better would be the real thing. Does anybody know if you can run CP/M from a minifloppy on an S-100?

Sean

MikeS
June 1st, 2008, 05:48 PM
Sure; eventually practically every system used 5 1/4" diskettes: CP/M, MSDOS, Apple, CBM, R-S, etc. although almost everybody had their own format and even the diskettes themselves were not all the same (Single/double/quad density, single/double sided, soft/hard sectored (10/16).

You have to remember that S-100 is only a specification for the bus that the cards plug into, and it doesn't say anything about the CPU, operating system, disk size/format, etc.

CP/M is also just a more or less standard interface between a program and the hardware, which could have any kind of CPU, diskette or hard disk (or neither), and any kind of display/console (local or remote terminal, memory-mapped, text or graphics, colour/mono, etc.)

So, both S-100 and CP/M don't really specify the actual system or what software will run on it, although unless it's all high level, the software would have to match the CPU.

Although the majority of S-100 boxes probably did run 8080 or Z80 CP/M with 8" or 5 1/4" disks, there were S-100 systems using 8086/8088s (PC), 6502 (Apple/PET/OSI), 680x0 (Motorola) etc., with various floppy and hard disks, controllers, monitors, etc. etc. Sometimes you could mix and match cards from different systems but often there were small or large compatibility issues.

DOS just stands for Disk Operating System BTW and not *necessarily* MS- or PC-DOS, at least not in those days.

m

Floppies_only
June 1st, 2008, 06:04 PM
Mike and everybody,

There is an eBay seller that was a computer dealer in the early eighties. This eBay seller is offering manual scans from that period on CD-ROM. I am going to buy them and look for peripherals that would be compatible.

Sean