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HIMEMV2 or equivillent PROM

Chuck(G)

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you can run program files from config.sys, at least in later versions of DOS (unless I'm slightly mistaken).

Yes, but they're run after device drivers have been processed, in the same way that SET statements are processed in the CONFIG.SYS file.

If I get a few minutes this afternoon, I'll make the driver mods, rather than waste time gumming the subject to death.
 

Chuck(G)

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I found some time to throw together CLEARMEM.SYS (attached).

Invocation is easy, just put it in your CONFIG.SYS file ahead of the USE!UMBS.SYS command. It takes two arguments, both in hex. The first is the starting segment address of an area to be zeroed; the second is the hex number of paragraphs to clear. CLEARMEM releases its memory after it clears, so it doesn't occupy any space permanently.

So, to clear the range between D000:0 and E000:FFFF, use the following statement in CONFIG.SYS:

DEVICE=CLEARMEM.SYS D000 2000

In other words, clear 8192 (decimal) paragraphs, or 128K starting at segment D000.
 

Attachments

  • CLEARMEM.ZIP
    3.7 KB · Views: 4

ibmapc

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That did it!!
Now boots everythime without the Parity Check. Thanks again Chuck.
And by the way, you are right, of coarse,I do need to learn assemly. I guess I've felt that it was beyond my mental abillities. Maybe you could recomend a good book? Something like Assembly X86 for old Dummies?

Best regards,

Greg

PS Boy o Boy, this 5155 is a real Hot Rod now!
 

Chuck(G)

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I hauled out one of my XT clones and looked at the motherboard. It appears to be a Turbo 640, or a close relative, with an ERSO BIOS.

One thing that caught my eye was a socketed 16-pin IC just to the right (looking from the rear) of the BIOS sockets, near the edge of the PCB. It turned out to be a 82S129 PROM, which is the Signetics equivalent of the 24S10 PROM on the 5160. I suspect, but haven't verified, that the HIMEMV2 mod will work as-is on this board.

Here's my question to the XT clone community at large.

If you have a XT clone motherboard with 4 x 9 chip RAM organization that accepts 256Kb DRAMs in at least the first two ranks, do you also have a socketed 16-pin bipolar ROM on your board?

Since the ERSO design was the reference design for most Taiwanese XT clones, I suspect the answer will be "yes". There are later designs where the last two ranks of RAM are replaced with 4464-type chips, but they're easily recognizable, as they don't have the "block" of 36 chips arrangement.
 

modem7

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Here's my question to the XT clone community at large.
If you have a XT clone motherboard with 4 x 9 chip RAM organization that accepts 256Kb DRAMs in at least the first two ranks, do you also have a socketed 16-pin bipolar ROM on your board?
I have just now examined five of my six clone XT motherboards (one is in storage). Only one of those five has the 4x9 RAM chip arrangement. 256Kbit chips in banks 0/1 and 64Kbit chips in banks 2/3. The motherboard is labeled "X'GOLDEN TURBO-BOARD".

Close to the RAM banks is a socketed PAL16L8ACN. Near to the PAL16L8ACN is a "256K/640K" jumper, of which one pin is connected to pin 18 of the PAL16L8ACN. That pin is grounded for 640K and is pulled high for 256K.

So, 20-pin, not 16-pin, and PAL, not PROM.
 

Chuck(G)

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Useful info, thanks. Another clone i looked at--a 10MHz turbo board--uses 2 banks of 41256 and fills out the remainder with 4464 and 4164 (for parity). Obviously some vendors followed the IBM model and others didn't.
 

MikeS

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Out of 6 loose MBs two of mine are the same as Modem7's, i.e. 18x256 + 18x64 with a 20-pin PAL (U103) at the end of the ROM row and a 256/640 jumper, although one PAL is a 14L4CN while the other is a 16L8ANC (which is maybe also what Modem7 meant).

I'm pretty sure I've got a few more in cases, including IIRC at least one 1024K version; I'll have a look if I get a chance.

So, do I gather from all this that if we put in one of these custom GALs we get usable UMBs on our XT clones, not just RAMdisk & print buffer memory?

Re Chuck's latest post which crossed mine in cyberspace, the rest of my boards are the same as his, i.e. 18x256, 4x4x64 and 2x64, both 10MHz and 12MHz. Also, these boards only have one 28-pin spare ROM socket instead of six like the above-mentioned boards, presumably for a larger all-in-one BASIC ROM.
 
Last edited:

Chuck(G)

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MikeS said:
So, do I gather from all this that if we put in one of these custom GALs we get usable UMBs on our XT clones, not just RAMdisk & print buffer memory?

Yup, with the UMB driver, you can load DOS high, along with drivers and TSRs. Pretty cool on a resource-limited system. EMM386 or HIMEM not required.
 

MikeS

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Yup, with the UMB driver, you can load DOS high, along with drivers and TSRs. Pretty cool on a resource-limited system. EMM386 or HIMEM not required.
Pretty cool indeed; I don't really need one myself, but I wonder if with possibly a little rearrangement of the I/O pins one of these GALs would be a direct drop-in replacement for those boards with a 20-pin PAL?
 

Chuck(G)

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Without the board on hand to trace out the circuitry or at least a schematic, it'd be pretty close to impossible for someone like me. But given one or the other, it'd be pretty straightforward, I'd think.
 

MikeS

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Without the board on hand to trace out the circuitry or at least a schematic, it'd be pretty close to impossible for someone like me. But given one or the other, it'd be pretty straightforward, I'd think.
Pshaw! Nothing's impossible for you!

Not much point though unless somebody's seriously interested as the OP was.
 

ibmapc

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Yup, with the UMB driver, you can load DOS high, along with drivers and TSRs. Pretty cool on a resource-limited system. EMM386 or HIMEM not required.
Minor Correction
Loading DOS high is not possible with this arrangement since there is no "HIGH" memory, only UMB. If I understand correctly, "HIGH memory" is the segment immediatly beyond 1 megabyte.

However, even with my setup, which incudes EGA and Hard Disk which both use portions of "Upper Memory", I am able to use one block of 128K of UMB. I can load dosdata, command.com, several device drivers, and TSR's in that 128K of UMB. My config.sys starts out as follows

device=c:\use!umbs\clearmem.sys d000 2000 (clearmem.sys Chuck(G)'s wonderful creation)
device=c:\use!umbs\use!umbs.sys
dos=umb
dosdata=umb
shell=c:\dos\command.com /h/e:512 c:\dos /p
devicehigh=c:\hotshot\fdd.sys
devicehigh=c:\dos\setver.exe
devicehigh=c:\dos\ega.sys

If I change the "dos=umb" to "dos=high,umb" most of the system kernal still loads in low memory, since there is no actual "HIGH" memory. However the "dosdata=umb" puts 17,800 bytes of the system kernal into UMB. And the "shell=command.com /h ..." puts all of command.com in UMB. Kind of inconsistent here, because one could interpret the /h as referring to "HIGH memory, but it actually refers to UMB, or "UPPER momory.

Check out the folowing View attachment 7318 This is the current memory configuration for my 5155. Note that I have 608,960 bytes of base memory free and there is still 91,184 bytes of "UPPER" memory available for more drivers and tsr's.
 

Chuck(G)

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Thanks for the correction. I'dve thought that DOS=UMB would result in most of DOS loading in UMB, but I guess not--it requires HMA and that isn't going to happen. Perhaps I should RTFM more...

:)
 

ibmapc

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Hey Chuck(G), or anyone else with knowledge about these things;
I'd like to play around with GAL Programming. Do you think one of THESE would work? Do you know anything about the software that comes with it. Would it be compatible with the JEDEC and/or EQN file that you included in the U44V2M.ZIP‎? If you don't like this one, is there one you can recomend?
 

Chuck(G)

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The TOP853 is cheap, and will do 20-pin and some 24-pin GALs (but not PALCE nor PEEL), but if I had to do it all over again, I wouldn't buy it unless what I wanted to do was to program EPROMs and EEPROMs. I'd want something to handle a wider array of programmable logic. The G540 is nearly as inexpensive, but handles a slightly wider variety; the Wellon seems to carry the biggest bang, but is also the most expensive.

If you want to buy my TOP853, I can probably make you a good deal on it--and I'll go buy the Wellon.

But yes, the TOP853 was used to program your U44.
 

ibmapc

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OK, Let me know what you want for it, and I'll see if my Wife will let me buy it!! Send me a PM when you come up with a number that makes sense. Remember, I still owe you a HUGE favor, so don't go to cheap!
 
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