robcfg wrote:I've run out of 27128's but I have a couple 27256's at hand. Can I use them for the Dragon?
Yes. Although the Dragon will only be able to access the last 16K of the EPROM.
The easiest way is to edit the ROM image using a hex editor, select all, copy and paste to create an image at the required size of 32768 bytes.
Last edited by KenH on Wed Oct 24, 2012 5:07 pm, edited 1 time in total.
robcfg wrote:I've run out of 27128's but I have a couple 27256's at hand. Can I use them for the Dragon?
Yes. Although the Dragon will only be able to access to last 16K of the EPROM.
The easiest way is to edit the ROM image using a hex editor, select all, copy and paste to create an image at the required size of 32768 bytes.
Great! I'll by trying it when I have a little time.
KenH wrote:Hi Steve,
Regarding your previous question, I'm not an expert on this issue, but I believe that any EPROM rated at 200ms or faster would work fine.
The AM27C128 150ms will surely be fine.
zephyr wrote:Ken, The original EPROMs in my Dragon 64 are HN4827128G's. Is this programmer capable of programming the HN6827128G's
The HN4827128G is a 27128 EPROM manufactured by Hitachi. However it's an older EPROM with a programming voltage of 21V vs. 12V in "newer" 27128 EPROM.
I'm not quite sure if the Willem supports 21Vpp programming. The specs say "21Vpp Modify Circuit" which I guess means you somehow need to mod the programmer's circuit.
Rather than buying a programmer that supports 21V eproms, its may be easier to find 12Vpp programmable eproms. Note that all these EPROMS use 5v for data reading, so they will work equally well on your real Dragon.
Search for the EPROM's datasheet and you will find its programming voltage listed there.
zephyr wrote:
and the 24 pin AM2732's mentioned above?
Another possibility would be to get (or build) a 24pin to 28pin adapter and user 12Vpp 28 pin EPROMS. You'll get the extra benefit of a dual rom device.
Cloud9 has such a product: http://www.frontiernet.net/~mmarlette/C ... apter.html It's advertised for dos but will also be OK for the Dragon 32's ROM.
I have a lot to learn about EPROM chips!
What can I use to replace the Hitach HN482764G in my original DragonDOS controller?
You can use practicaly any 28 pin EPROM both for the Dragon ROMS and for DragonDOS. For the Dragon ROMS (which are 16K) you must use a 27C128 or higher, and for DragonDOS (which is only 8K) a 27C64 or higher.
In the name of an EPROM, the "C" after the 27 indicates that it is a CMOS EPROM. These require a much lower performance than the old NMOS EPROMS and can function with lower programming voltages (12.5 volts) . Since both chips are otherwise compatible, the old NMOS EPROMS can be replaced with CMOS EPROMS of the same size (e.g. a 2764 can be replaced by a 27C64)
The 2 or 3 digits after that represent the EPROM size, in bits. So a 27C128 is 128 bit = 16k, and 27C64 is 64 bits = 8K.
You can use any size that is equal or larger than your existing EPROM. The Dragon will only "see" the last 8K/16K of data.
So the DragonDos has a HN482764G eprom, which is a 2764 -8K. You can replace it with 27C64, 27C128, 27C256 or even a 27C512.
zephyr wrote:
I would really like to buy the GQ-4X, but I want to be sure that its capable of programming all of the EPROMs mentioned in my previous posts.
How does this programmer get its 25 volt supply (USB port is only 5v). Would I need to buy a third party 25v power supply?
I don't know this programmer from experience, but my guess is that it uses a "voltage pump" to generate the programming voltages from whatever is available via the USB cable. That's the normal trick, anyway. All my old programmers operated in this manner.
No, you can't. Mask programmable ROMs are programmed during manufacturing. PROMs can be programmed once with a programmer. EPROMS can be programmed and subsequently erased using UV light. EEPROMS can be programmed and erased electrically.
rolfmichelsen wrote:No, you can't. Mask programmable ROMs are programmed during manufacturing. PROMs can be programmed once with a programmer. EPROMS can be programmed and subsequently erased using UV light. EEPROMS can be programmed and erased electrically.
-- Rolf
My apologies, Rolf. I deleted my post because I had found the information elsewhere. Thank You for the information.
The awesome GQ-4X programmer arrived early this morning, and it works like a charm (less than 4 seconds to burn and verify 16K on a 27C128). I am now the proud owner of a Dragon 64 with HD63C09E processor and Steve Woolham's Enhanced Dragon 64 ROMs v3.0. I can now verify that the v3.0 ROMs work perfectly under real Dragon 64 hardware, and are a joy to work with. I am now looking forward to experimenting with Steve Woolham's DragonCoCo ROMs.
I can now verify that the v3.0 ROMs work perfectly under real Dragon 64 hardware, and are a joy to work with. I am now looking forward to experimenting with Steve Woolham's DragonCoCo ROMs. 
