Upgrading XT-compatible computer 8088-2 8Mhz into NEC V20 10Mhz

[musicforlife]

In my EGA computer, Hyundai Super-16T, it's 8088-2 processor and with dip switches it's able to change between 4.77Mhz to 8Mhz. There are a few EGA games that would need at least a slight boost so could I upgrade it into 10Mhz? Does V20 8Mhz make any difference to 8088-2 8Mhz? I don't need 4.77Mhz option because I have already IBM 5150 for those CGA games.

The motherboard contains two crystals: Sunny 24.000 and Sunny SCO-010 1.843200Mhz. There's also 14.31818MHz crystal but that is along with the trimmer which I presume is the same as in IBM PC/XT reserved only for CGA composite output adjustment.

I am only worried that the processor is directly soldered into motherboard without socket so does it withstand desoldering?

 

[PeterNC]

Why risk it? Use a 286 for EGA. You can use a slowndown TSR to get it to 8088 10MHZ performance.

 

[musicforlife]

Why risk it? Use a 286 for EGA. You can use a slowndown TSR to get it to 8088 10MHZ performance.

My 286 computer is reserved for 8/16Mhz VGA games. I wouldn't want to buy again another 80€ computer just to play a few EGA games that are too slow in 8088 8Mhz.

 

[Chuck(G)]

It depends on the software, but a V20 at the same clock frequency will generally give around a 15% performance improvement. You might try replacing that 24MHz XCO/crystal with a 30MHz one and the V20, but there be dragons in that--you're gambling on the support chips being able to run at the slightly faster clock.

The V20s are surprisingly tolerant of faster clocks. I've been running a 5MHz V20 at 8MHz for quite some time without problems.

 

[krebizfan]

Removing a soldered in CPU can be done. If you haven't done a lot of desoldering before, I recommend not trying. Make a mistake and there is a possibility of destroying the board. The typical process also requires snipping the legs off the soldered in CPU so you will lose that as well.

You will be putting in a lot of effort to handle the relatively small number of EGA games that won't work on a 286 with VGA.

 

[Ruud]

There's also 14.31818MHz crystal but that is along with the trimmer which I presume is the same as in IBM PC/XT reserved only for CGA composite output adjustment.

No, it is needed for the CPU as well so it can run at 4.77 MHz. And even if you run at 8 MHZ, there is a possibility that the system slows down to 4.77 MHz the moment you use the floppy. May be even with ard disk drive accesses, I'm not sure about that. Oh, just popped up: it is used via via by the 8253 timer.

 

[Ruud]

The typical process also requires snipping the legs off the soldered in CPU so you will lose that as well.

Why do you say that? I only cut the legs if I'm 100% sure that an IC is broken or I have enough spares to replace it: it simplifies the de-soldering process indeed. Otherwise you have to be 100% sure that all legs are de-soldered otherwise you run the risk of pulling a PCB wire when pulling the IC from the board. Checking is easy: just wiggle the leg and see if the part at the IC side wiggles as well.

 

[Trixter]

In my EGA computer, Hyundai Super-16T, it's 8088-2 processor and with dip switches it's able to change between 4.77Mhz to 8Mhz. There are a few EGA games that would need at least a slight boost so could I upgrade it into 10Mhz? Does V20 8Mhz make any difference to 8088-2 8Mhz? I don't need 4.77Mhz option because I have already IBM 5150 for those CGA games.

You can replace the 24 MHz crystal with a 30MHz crystal and use a 10 MHz-rated NEC V20, however this may stress other components (memory) or possibly have side effects (dram refresh). The boost is small enough that I don't think you'd risk damage. I'm assuming the 4.77 MHz mode uses the 14.31818 crystal so leave that alone of course.

I am only worried that the processor is directly soldered into motherboard without socket so does it withstand desoldering?

Yes.

What EGA games do you need a speed boost for? Some games are slow simply because they don't update EGA in a sane manner; a faster CPU won't help very much with that.

My 286 computer is reserved for 8/16Mhz VGA games

Wait, what? If you have a 286 with VGA, you don't need to perform this mod at all. VGA emulates EGA; just play your games there.

 

[musicforlife]

You can replace the 24 MHz crystal with a 30MHz crystal and use a 10 MHz-rated NEC V20, however this may stress other components (memory) or possibly have side effects (dram refresh). The boost is small enough that I don't think you'd risk damage. I'm assuming the 4.77 MHz mode uses the 14.31818 crystal so leave that alone of course.



Yes.

What EGA games do you need a speed boost for? Some games are slow simply because they don't update EGA in a sane manner; a faster CPU won't help very much with that.



Wait, what? If you have a 286 with VGA, you don't need to perform this mod at all. VGA emulates EGA; just play your games there.

I want to play all of my CGA and EGA games in authentic environment. I already have 286 computer reserverd for slow VGA games and I don't want to buy again another computer and instead use this Huyndai 8088-2 computer. This Hyundai is real EGA setup complete with Hyundai's EGA monitor.

The EGA games that need boost are for example, Chagunizu, Apogee's arctic adventures and monument of mars. Those games works fine in 286 8mhz computer but do not work if the processor is too fast hence they won't work in my 386-486 EGA setup. Sure, getting another 286 for EGA would fill the gap but I already have like 7 computers so I really don't want to get yet again another computer to save the space.

 

[VileR]

The EGA games that need boost are for example [...] Apogee's arctic adventures and monument of mars.

As far as I know those two are CGA.

There are certain advantages to running EGA games on an EGA setup, rather than VGA (no refresh-rate mismatches, since in 200-line modes you get the expected 60Hz; no double-scanning of the output, so dithering looks less 'coarse').

 

[musicforlife]

As far as I know those two are CGA.

There are certain advantages to running EGA games on an EGA setup, rather than VGA (no refresh-rate mismatches, since in 200-line modes you get the expected 60Hz; no double-scanning of the output, so dithering looks less 'coarse').

Yes, my EGA cards contains also CGA compatible mode so it's very useful for later era CGA games that requires more power than my IBM 5150 can offer.

I particulary love the scanlines of 200 line modes of EGA and CGA.