9 Nov
2007
9 Nov
'07
10:50 p.m.
Date: Fri, 9 Nov 2007 16:54:18 -0500 (EST)
From: bpope at wordstock.com (Bryan Pope)
Subject: Re: Commodore PET
DRAM!? In a PET?! That is crazy talk! ;) There was
never even DRAM in
the C64... Although I believe the SuperCPU used DRAM memory, but that
was third-party.
--------
Say what?
AFAIK all their stuff used DRAM except for the first two 8K versions and the
oddball VIC-20 (or VolksComputer as it was known in Germany to avoid the
connotations of a certain homonym of VIC, pronounced 'fick' in German...),
which they probably produced to use up 2114s left over from the old PETs ;-)
I've never owned or seen any 8K PETs other than the 6540/6550 version,
but as Ethan says there was a 2114 version with industry-standard ROMS;
=16K units were all DRAM AFAIK. Once DRAM caught on it
didn't make
economic sense to use SRAM in any quantity; look at S-100 boards.
m
9 Nov
9 Nov
11:18 p.m.
On Fri, Nov 09, 2007 at 10:50:08PM -0500, M H Stein wrote:
Sure. By the time of the 16K and 32K PETs, there were early examples
of 8kbit SRAMs, but those only made economic sense in certain niches.
Just look up how much of the motherboard in an 4K/8K PET is RAM vs
a 16K/32K PET... between package count and package size, the economics
of fields of SRAM vs DRAM are obvious.
Using DRAMs for 16K, 32K, 48K, 64K... is an especially big win on
designs like the Apple II where the video circuit provides "free"
refresh.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 10-Nov-2007 at 04:10 Z
South Pole Station
PSC 468 Box 400 Temp -40.7 F (-40.4 C) Windchill -60.4 F (-51.3 C)
APO AP 96598 Wind 5.2 kts Grid 94 Barometer 693.5 mb (10123 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
AFAIK all their stuff used DRAM except for the first
two 8K versions and the
oddball VIC-20 (or VolksComputer as it was known in Germany to avoid the
connotations of a certain homonym of VIC, pronounced 'fick' in German...),
which they probably produced to use up 2114s left over from the old PETs ;-)
I think *all* PETs used 2114s for the video memory at $8000. The 2016 or
6116 wasn't out early enough to get worked into them, plus, from the tales
of the Jack Trameil days, I'm sure they had trainloads of 2114s and were
ordered to use them up rather than engineer in a new part. The 1540 and
later floppy drives, though, _did_ use 2016/6116 SRAMs rather than 2114s,
possibly just to have enough RAM to be useful and still fit inside the
drive case.
I've never owned or seen any 8K PETs other than
the 6540/6550 version,
but as Ethan says there was a 2114 version with industry-standard ROMS;
And I _think_ they sold a few 8K PETs with 4kbit DRAMs, but those weren't
very popular. Certainly the manufacturing margins were minimal compared
to what they could get for a 16K PET using eight 4116s and everything else
being identical.
=16K units were
all DRAM AFAIK. Once DRAM caught on it didn't make
economic sense to use SRAM
in any quantity; look at S-100 boards.
8:05 a.m.
New subject: PET SRAMs
On Sat, Nov 10, 2007 at 11:53:52AM +0000, Pete Turnbull wrote:
On 10/11/2007 04:18, Ethan Dicks wrote:
Ah, yes. It did. Sorry about the over-generalization.
All of the *later* PETs used 2114s, but not the earliest model.
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 10-Nov-2007 at 13:00 Z
South Pole Station
PSC 468 Box 400 Temp -40.4 F (-40.2 C) Windchill -55.0 F (-48.3 C)
APO AP 96598 Wind 3.3 kts Grid 71 Barometer 692.2 mb (10171 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
I think *all* PETs used 2114s for the video memory
at $8000.
Although the ones that used 6550s for main RAM used them for the video too. 
8:56 a.m.
New subject: PET SRAMs
On 10/11/2007 13:05, Ethan Dicks wrote:
On Sat, Nov 10, 2007 at 11:53:52AM +0000, Pete
Turnbull wrote:
I expected you knew that; I was just being pedantic :-)
--
Pete Peter Turnbull
Network Manager
University of York
On 10/11/2007 04:18, Ethan Dicks wrote:
Ah, yes. It did. Sorry about the over-generalization. I think *all* PETs used 2114s for the video
memory at $8000.
Although the ones that used 6550s for main RAM used them for the
video too.
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