View Full Version : Overclocking an XT?

July 18th, 2006, 02:07 PM
Is it possible to overclock a PC-XT?

July 18th, 2006, 02:08 PM
Probably not a whole lot.

Your best bet is probably to replace the 8088 with a NEC V-20.

July 18th, 2006, 02:18 PM
yeah, I have a NEC-V20, but I read that there were some models that run at 8 MHz, so maybe it is possible...

July 18th, 2006, 02:22 PM
Well, if you're willing to replace the motherboard I've seen 8MHz XT class boards before. I just don't think that the IBM XT board itself can be so easily overclocked.

I could be wrong, though. :)

July 18th, 2006, 03:06 PM
Look for 'PCSprint.LZH' at Chatnfiles. (A Google search on PCSprint and ChatnFiles will get you to it.) It's a relatively simple speed modification for PCs and XTs, and can work on the the PCjr as well.

You will need to do some homework to make that archive file readable. The drawings are in Epson printer code format, which works really well on an old Epson printer but not on anything made in the last 10 years. ;-)

July 18th, 2006, 04:14 PM
OK, I got it :thumbsup: , but now I have 2 find out how to make those files readables... :confused:

July 18th, 2006, 04:42 PM
If you're using XP, then double-click the file & there should be a selection to search the web for a probram to use it. (I don't know what it says word for word, but it's something similar to that)

Microsoft.com has a big database of file extentions, so chances are, doing the above should help you out, maybe even provide you w/ a link!

July 18th, 2006, 04:50 PM
If you have DOS or an older Windows (up to 98 at least), prtview (http://ftp.45.free.net/pub/softweyr/utils.html) can display most of the Epson files on screen, including the graphics. Running in a DOS shell, you can press Alt+Print Scrn to get a screenshot of every page to paste into e.g. Paint.

July 18th, 2006, 04:51 PM
The files don't have extensions... so I have no idea if there is any way to convert them...

July 18th, 2006, 04:54 PM
My solution works, for all but two of the graphical files.

July 18th, 2006, 05:06 PM
ok, I downloaded a file named "prtview.exe" but when I run it, it displays some weird caracters... how should I use it?

July 18th, 2006, 07:47 PM
Here - try this version instead. I'll leave it up for a few days:


July 19th, 2006, 07:49 AM
Thanks! ;)

August 11th, 2006, 02:26 AM
Well here comes where I have my Nick from...

Once I owned a Twinhead 8086 Desktop PC with a 40 Mb self-parking MFM harddrive.

It had 640Kb internal RAM who I expanded to 720Kb with some more chips and tinkering with the Software inside the BIOS chip (Actually, a copy in an EPROM).
It had a built in 256 color capable VGA videocard, and I added an 8-bit soundcard (Mono, but hey, it gave more then that tweaker onboard!)

I desoldered the quartz oscilator from the Mainboard and resoldered a 125% version back.
Luckily the CPU was a ceramic type so I crazyglued a large heatsink to it.
I managed to get a stable 12 MHz out of it... (It WAS an 8 )
But, the RTClock was way off! (No matter!)

I managed to get an 1.44 Mb 3.5" floppydrive to work. (Does anyone still knows the command Drivparm in Config.sys?)

With that I was able to get MS-DOS 6.0, Windows 3.0, and WordPerfect 4.2 and some simple games to run on that thing.

If only the Monitor did not Zapped the system when it went out with a bang....
It was way beyond its time!!!


August 11th, 2006, 12:00 PM
there were versions of the 8088 that ran as high as 16mhz, probably faster too. But...to utilize that in yer puter all the other chips would have to be capable of the same speed (well some anyway, depending on if they're clocked or not). There were mobos that ran that high as I recall. Of course you can try bumping it up slowly with a crystal replacement. After all the original IBM PC/AT 5170 came off the conveyor belt at 6mhz. For whatever reason, those 80286's were rated at 6mhz, but you could just plop in a 16mhz crystal (which was divided by 2 to get the cpu clock) and run it at 8mhz. Even the ITT Xtra XP, my first compatible was set at 6mhz. And the crystal wasn't even soldered in - all you had to do was pull the old one out.
I remember some discussion somewhere about it, whether it was truly ok to bump up the speed that way I don't remember (you may, and probably were shortening the life span of the chip that way). But the 8088/8086 is a slightly different beast, although obviously from the same basic time period.

August 11th, 2006, 12:02 PM
"Once I owned a Twinhead 8086 Desktop PC..."

dUDE, what be that?? I'm curious about anything not quite run of the mill in that category (8086 as opposed to an 8088).

August 13th, 2006, 12:11 AM
The 8086 was the more expensive version who has an internal 16-bit register.
The 8088 was the (Deliberately) crippled one who was 8-bit, and cheaper that way.

August 13th, 2006, 06:41 AM
Well, close, but not quite perfect.

Internally the 8088 and 8086 are exactly the same. Same registers, same capabilities, etc. Registers are either 8 or 16 bit depending upon how you look at them.

When connecting to the rest of the system the 8086 is a much better processor. The 8088 connects to the rest of the machine using an 8 bit bus while the 8086 connects to the rest of the machine using a 16 bit bus. The 16 bit bus of course provides 2x the throughput to memory, if the memory is on that bus. The 8086 also has a 6 byte instruction prefetch buffer instead of the 4 byte instruction prefetch buffer that the 8088 has, which makes it slightly faster.

The 16 bit bus requires a much different motherboard though, one that looks more like an AT. PC cards designed for the original PC are only 8 bit cards, and except for the memory on the motherboard memory is added using those 8 bit cards. On a motherboard designed for an 8086 to get the best performance you need two buses - a 16 bit bus for memory and an 8 bit bus for regular PC cards. Adding memory on the 8 bit bus would be slower, or perhaps not work at all.

The 8088 allowed for less expensive motherboards and cards, while giving up some performance. The PC AT design went to a full 16 bits, both in the processor and on the bus.

Twinhead - your English is fine. Your handle is the same as a that of a well regarded Taiwanese manufacturer from the early 90s - was that your inspiration?

August 14th, 2006, 01:11 PM
"Once I owned a Twinhead 8086 Desktop PC..."

"dUDE, what be that?? I'm curious about anything not quite run of the mill in that category (8086 as opposed to an 8088)."

"The 8086 was the more expensive version who has an internal 16-bit register.
The 8088 was the (Deliberately) crippled one who was 8-bit, and cheaper that way."

dUde...I was referring to the computer. Not a run of the mill Taiwanese clone if it sported an 8086. Picture or whatnot might be nice.