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Other systems equalling an IBM PC's speed

G

Great Hierophant

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I am trying to compile a list of systems that run or could be run at exactly the same speed as an IBM PC. This means that the system is running on a Intel 8088 processor running at 4.7727MHz accessing DRAM and ROM (up to 640K) without wait states (4 CPU clock cycles).

The list includes:
IBM PC
IBM PC/XT
IBM PC Portable
IBM PCjr. (>128K)
Tandy 1000
Tandy 1000A
Tandy 1000HD
Tandy 1000EX (Slow mode)
Tandy 1000HX (Slow mode)
Tandy 1000SX (Slow mode)
Tandy 1200
Compaq Portable
Commodore PC-1
Commodore PC-10
Commodore Colt
Commodore PC-20
Columbia MPC
Columbia VP
Eagle Spirit
Franklin PC-5000
Franklin PC-6000
Franklin PC-8000

Many systems don't just quite cut it. Some use 8086s or V20s. Others clock their 8088s at a higher speed and have no feature to slow the processor down. The IBM PC Convertible would have made the cut had it used DRAM instead of faster SRAM.
 
Chuck(G) said:
Eagle PC
Eagle PC 2

...scads of unremarkable Taiwanese PCs...
Click to expand...

Yes, I was going to add this. A number of Asian (mostly Taiwan) companies cloned the PC and sold into Australia and New Zealand (and Europe?). They probably were a real minority in North America but not so much in the rest of the world (their models were about 2/3 the price of the IBM machine.

Even more Asian companies cloned the AT!

Tez
 
Great Hierophant said:
I am trying to compile a list of systems that run or could be run at exactly the same speed as an IBM PC. This means that the system is running on a Intel 8088 processor running at 4.7727MHz accessing DRAM and ROM (up to 640K) without wait states (4 CPU clock cycles).
Click to expand...

That class of machines accesses ROM in 3 cycles, not four. That's one of the reasons the exact same "cga snow avoidance" code copied to RAM does not work -- too slow. You have to get creative with 1-byte opcodes and caching a word into a register to truly avoid all CGA snow. But the ROM code works because it's in ROM. (The ROM cga snow code is not bad code, it's optimized for size.)
 
Panasonic Sr. Partner

IBM PCjr can be added to the list if you allow RAM expansions. A PCjr with a RAM expansion will run at the same speed as a PC. (Otherwise, programs run out of video ram with additional wait states -- ick).
 
Trixter said:
Panasonic Sr. Partner

IBM PCjr can be added to the list if you allow RAM expansions. A PCjr with a RAM expansion will run at the same speed as a PC. (Otherwise, programs run out of video ram with additional wait states -- ick).
Click to expand...

Only programs in the expansion memory of a PCjr run faster. Anything that's in the first 128k (DOS, booter games, etc.) will still be slowed down by the video circuitry.

Leading Edge had machines that were dual 4.77Mhz/7Mhz. All Tandy 1000s except the RLX and RSX can run at 4.77 Mhz. The 128k models (original 1000 and EX/HX) run slower than normal just like the PCjr. There were also a number of 8088 laptops that could be included.

Do we count all the 286/386/486 machines with turbo buttons that can be set to 4.77 Mhz?
 
tezza said:
They probably were a real minority in North America but not so much in the rest of the world (their models were about 2/3 the price of the IBM machine.
Click to expand...

At least where I was at the time (Silicon Valley), the clone vendors were all over the place. Just about anyone who could talk a relative back in the Old Country to pack a shipping container full of clone goodies seemed to do so--and competition was fierce.

I got my wife an XT clone from one of those outfits with a "lifetime" warranty. Not only that, but if I bought a hard disk controller, they'd throw in a free hard drive! I still have the Xebec controller and hard drive (an ST-506, which required some patching to the HD BIOS to get it to work, since it doesn't have buffered seek. Of course, the guy who sold her the system didn't tell her that...) the clones were sold at swap meets, on the TV, in the newspapers, you name it.

If the OP wants a more exhaustive list, I can consult my PCTJ product listing of the time.

One big Far East player not mentioned was DTK. I think Everex sold XT compatible systems; I've still got a manual for a Multitech PC. Tatung had one...the list is very long...
 
Well, that's not true either. The answer is 'it depends'.

A PCjr with 128K is much slower than a PC because the video controller is stealing cycles from the CPU to refresh the screen, and the video controller has a higher priority.

A PCjr with more than 128K can actually be marginally faster than a PC 5150 when operating out of RAM because each new memory expansion sidecar has its own DRAM controller for refresh, as opposed to the PC 5150 which uses a DMA channel to do it for all memory at the same time.

And a PCjr operates out of ROM faster than a PC. Which is important when in BIOS routines or in Cartridge BASIC.

Everybody should own, read and understand their technical reference manuals. They are priceless for information like this.
 
Chuck(G) said:
If the OP wants a more exhaustive list, I can consult my PCTJ product listing of the time.

One big Far East player not mentioned was DTK. I think Everex sold XT compatible systems; I've still got a manual for a Multitech PC. Tatung had one...the list is very long...
Click to expand...

Which is why I don't understand the value of the original question. It is a lot easier and more interesting to enumerate machines that did *NOT* run at the same speed or were not 100% compatible. There were so many reference designs for 100% compatible clones that it would be impossible to list them all.

Some excellent examples - any machine with an 8086 instead of an 8088. These are faster by definition, even though they are usually highly compatible.
 
mbbrutman said:
Which is why I don't understand the value of the original question. It is a lot easier and more interesting to enumerate machines that did *NOT* run at the same speed or were not 100% compatible. There were so many reference designs for 100% compatible clones that it would be impossible to list them all.
Click to expand...

Good point--any list we could compile today probably would not be exhaustive. A lot of builders of the time existed only briefly.

A more instructive list might be a list of computers that were marketed during the rise of the 5150/5160 that were supposed to be "compatible", but were anything but. For example, the Sanyo MBC550.
 
DEC Rainbow 100 ???

DEC Rainbow 100 ???

My ex wife made me get rid of mine (which were picked from the trash) a long time ago but the DEC Rainbow had both an 4.81 MHz 8088 chip and a Z80 chip. It was made to run both CP/M and DOS (and CP/M-86?), although the DOS was actually slightly different from IBM PC-DOS (or MSDOS), including the fact that the floppy disk format was different. Which meant IBM DOS users had to kludge a networking solution (possibly through DECnet) to actually get functioning PC software. This was despite paying a rather high premium to get this dual CPU solution in the first place. It also had an internal bronze-colored metal frame. I'm not sure what metal it really was, but it seemed like it could stand up to a tank. They don't make them like that anymore! ;)
 
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Great Hierophant said:
I believe that Tandy 1000s without DMA should run slower than a PC, but with a Tandy RAM expansion upgrade, which adds a DMA chip, the DMA will be used for RAM refresh and disk transfers, making the system theoretically as fast as a PC.
Click to expand...

Of course Tandy 1000s with DMA are as fast as a normal 8088 PC. If you read that article though, they must have been using one with 128k and no DMA, since they talk about running Touchdown Football, a PCjr game that won't work on Tandys with >128k because the video memory isn't where the game expects it to be.
 
From what I recall, the Olivetti M24 was as close to clone of a PC as you could get. It's BIOS was truly 100% compatible and spec wise it was nearly the same with the exception that a few cards (I/O and Video) were integrated into the mainboard.
 
The exact speed of an IBM PC 5150 can be surprisingly elusive. I tried a Tandy 1000 SX in slow mode, which operates its 8088 at 4.77MHz. The benchmark program MIPS, v1.20 gives scores ranging from .98-1.01 times as fast as an IBM PC. My real IBM PC 5150 reports 1.00 results in every category on that machine. I also tried an IBM PC/XT motherboard and got 1.00 in all but one test, where I got a .99.
 
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