Talk:Datapoint 2200

message: Why wasn't that correct? I noticed someone made the change from KB to KiB here a while ago then it was rejected. Let's GET some consensus on this, folks! mike4ty4 (talk) 00:41, 4 January 2008 (UTC)
replies: text: For RAM KiB and KB are equivalent even in 2008.  Any article referring to KB of RAM on computers prior to 1995 are all using 1024 bytes and there is no confusion. Don't know of any machines with KB's of RAM after 1995 but if you find some embedded systems with KB I'm pretty sure it's 1024.  KB is historically accurate for the description of RAM on this machine and no need to revise for historic reasons.  Alatari (talk) 15:45, 8 January 2008 (UTC)
thread_title:  KB instead of KiB? 

message: Supposedly, the difference between using the intel 8008 and Datapoint's discrete TTL implementation is an 8x11 motherboard and an 11x14 motherboard. The supporting logical required for the intel 8008 being a notable size cost.
131.107.0.73 (talk) 17:36, 19 May 2011 (UTC)
replies: text: If this could be doucmented it might be worth noting either in this article or in the 8008 article. But the board size doesn't appear to be the reason the 8008 wasn't used. --Wtshymanski (talk) 20:47, 19 May 2011 (UTC)
thread_title:  Size difference i8008 motherboard to discrete motherboard 

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thread_title:  External links modified 

message: The article says "It was presented by CTC simply as a versatile and cost-efficient terminal... However, enterprising users... realized that this so-called "programmable terminal" was equipped to perform any task a simple computer could."
Leaving aside the self-contradiction there ("simply (a) terminal" vs. "so-called programmable terminal"), the implication is that CTC tried to hide the programmability of the system, but somehow customers figured it out. In fact, the marketing of the system featured its programmability from the beginning.
The system documentation, for example, included a programmer's reference manual at least as early as August 1971. That edition included a program listing for the in-ROM boot loader dated "02/05/71". 
Microcomputer companies of the day, including HP, simply didn't want confuse buyers used to the notion that a "computer" was a huge expensive thing. HP, for example, referred to its BASIC-programmable 9830 as a "calculator," but of course it didn't try to hide the fact that it had BASIC in ROM, supported multiple peripherals including tape storage, and so on.
: It wasn't just a matter of "confused buyers." Sometimes it was institutional policy. If you worked for a university or a large corporation, and you wanted to purchase a "computer," it was might automatically be classified as capital equipment. Getting approval to purchase a "calculator" for the exact same price could be much easier. 173.75.33.51 (talk) 19:16, 9 July 2020 (UTC)
replies: text: "Datapoint: The Lost Story of the Texans Who Invented the Personal Computer", by Lamont Wood, appears to indicate that the initial marketing was mainly as a terminal that could run any of a number of emulators, but that a CTC salesperson, Dave Gust, got the idea of marketing it to Pillsbury as a computer they could use at their chicken farms to process payrolls, after which CTC decided to sell it as a computer.  (It also says they'd developed an ad to sell it as a computer, but they ran out of money and couldn't run it.) I've updated the article, using that book as a reference. Guy Harris (talk) 22:02, 14 September 2019 (UTC)
thread_title:  Programmability wasn't a secret 

message: From the article: "Even though the Datapoint 2200 processor design employed a bit-serial microarchitecture, operating one bit at a time, it performed faster than the Intel 8008 microprocessor which employed an 8-bit parallel microarchitecture" "Datapoint 2200 Version II (CTC's parallel design) was much faster than the TMC 1795, which was slightly faster than the original serial design of the Datapoint 2200, which in turn was considerably faster than the 8008."
The serial design of the Datapoint 2200 version I is not faster than the Intel 8008. Even though the article matches the reference cited, the cited reference is incorrect. Although the Datapoint 2200 version I is somewhat faster than an 8008 on many instructions, any reference to the 2200's shift-register memory incurs a giant 520µs delay. Also any JMP, CALL, or RETURN can incur a variable delay up to 520µs depending on the distance to the new address. The parallel-architecture Datapoint 2200 version II is much faster than either. Compare the instruction times:
Instruction	Instruction	Instruction	Instruction	Instruction	Description                 	Datapoint 2200 ver I µs	500 kHz Intel 8008 µs	Datapoint 2200 ver II µs
ADB        	ADB        	ADB        	ADB        	ADB        	Add B to A                  	16                     	20                   	3.2
ADI nn     	ADI nn     	ADI nn     	ADI nn     	ADI nn     	Add nn immediate to A       	16                     	32                   	4.8
ADM        	ADM        	ADM        	ADM        	ADM        	Add memory to A             	520                    	32                   	4.8
JMP nnnn   	JMP nnnn   	JMP nnnn   	JMP nnnn   	JMP nnnn   	Jump to nnnn                	24-520                 	44                   	6.4
CALL/RET   	CALL/RET   	CALL/RET   	CALL/RET   	CALL/RET   	Call and Ret combined       	520                    	64                   	9.6
Rcc (false)	Rcc (false)	Rcc (false)	Rcc (false)	Rcc (false)	Conditional return not taken	16                     	12                   	3.2
Page 8-11 of the Datapoint 2200 Programmer's Manual (August 1971) gives an assembly language example of a delay routine. The manual states that the delay routine decrements the delay counter at a rate of 2,000 counts per second. A 500 kHz Intel 8008 will execute this code at a rate of 5,319 counts per second, over twice as fast!
To show a most extreme example of the speed difference, I wrote a routine that would clear a 256 byte buffer located on a 256 byte boundary. The loop is just five instructions but unavoidably includes LMB and JFZ instructions, which are very slow. The 2200 version I will take about 266ms to execute. A 500 kHz 8008 will execute it in just 37ms, seven times faster! BTW: Using the expanded 8008 instruction set, the routine could be reduced to just three instructions, executing in 24ms.
How do we correct this error without violating Wikipedia sourcing rules? RastaKins (talk) 18:30, 3 June 2024 (UTC)
thread_title: Datapoint 2200 not faster than Intel 8008