Altair 8800, 8800A, 8800B??

From: James Willing <jimw_at_agora.rdrop.com>
Date: Thu Mar 5 00:01:58 1998

On Wed, 4 Mar 1998, Bob Wood wrote:

> Can someone educate me as to how the 8800, the 8800A
> and the 8800B differ?
> I would really like to know about all the differences
> in the three.

Short form: (more or less)

The 8800 was the original machine from MITS. Standard config was a 4 slot
backplane, a rather small capacity power supply, front panel, 2mHz 8080
CPU card, and depending on when you bought it either no memory, or with a
256 byte (expandable to 1k) static memory card. No I/O other than the
switches and lights on the front panel. ...and painfully small toggles on
the front panel switches. And of course the 80 or so individual wires
that connected the front panel to the backplane.

(let's not get nitpicky... I'm just listing the base configs as I recall
them. Pictures, notes, and price list images on my web pages)

The 8800a was a slightly uprated version of the 8800. Same front panel
and CPU card, a slightly higher capacity power supply, and longer
flattened toggles on the front panel switches. (minor cosmetic changes to
logo plate)

The 8800b was the machine reworked for more serious (read that: business)
purposes. A very much higher capacity power supply (which was made
available briefly as a retrofit for the 8800/8800a systems), 18 slot
backplane, a new CPU card (still a 2mHz 8080) and front panel interface
board which now connected to the display (front) panel with a pair of
ribbon cables, and additional functions on the front panel allowing the
operator to load and display the contents of the CPUs accumulator on the
front panel, do direct I/O to/from a port on the front panel, and added
the option to make the data lights on the panel operate in one of three
modes.

1) standard - unlatched data bus indication
2) port 377 - latched display of output to port 377 (FF if you prefer)
3) I/O - latched display of I/O to/from any port

Complete new cosmetic layout of front panel.

And... (to round it all out)

The 8800b Turnkey. Same as 8800b but without the display (front panel)
controls and lights. Front panel interface card replaced by the "turnkey"
board which held a boot loader EPROM. Front panel controls reduced to
run/stop switch, reset/clear switch, and a keyswitch for power.

-jim
---
jimw_at_agora.rdrop.com
The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174
Received on Thu Mar 05 1998 - 00:01:58 GMT

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