What if,... early PCs (was: stepping machanism

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sat Apr 10 03:34:31 1999

-----Original Message-----
From: Fred Cisin (XenoSoft) <cisin_at_xenosoft.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Friday, April 09, 1999 5:34 PM
Subject: Re: What if,... early PCs (was: stepping machanism


>On Fri, 9 Apr 1999, Allison J Parent wrote:
>> <Double density was NOT readily achievable in 1978. And the poor quality
>> My dog, don't tell DEC that or intel.
>
>Sorry, I should have said that it was not readily achievable for RADIO
>SHACK, not that it wasn't possible. It took RS a few more years before
>they were ready to have MFM in one of their consumer level machines.
>RS's early FM had some data separation problems; I assume that that was
>due to trying to keep the cost too low?
>
The RS people had their heads wedged, probably due to politics. They used a
strange mix of parts, seemingly cobbled together from various vendors' app
notes. Their FDC used a TI TTL VCO, a Motorola phase detector, and a
Western Digital controller chip. Additionally they used some wierd TI clock
generator and some other stuff I couldn't justify. Their clock recovery
circuit was pretty poor, i.e. poorer than average, and cost about 6x what I
was used to seeing. Their dynamic memory handling wasn't any sort of slick,
nor was their video circuit.

They could have used a circuit similar to what the Xerox 820 had from day 1.
It was an old design from a simple terminal and would freuently work on a
modified TV set, which is all RS was shipping anyway. It's clear that there
was politics and corruption at the top.

Dick

>
Received on Sat Apr 10 1999 - 03:34:31 BST