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Post by nonefornow on Sept 25, 2014 14:53:31 GMT
That's what the C=128 box says.
Since there were only two REU made by Commodore for C128 - 1700 with 128K and 1750 with 512.
Does it mean that no-one contemplated to have other REU with more memory?
Or that really the C=128 can only handle 512K extra?
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Post by VDC 8x2 on Sept 25, 2014 22:31:20 GMT
I think the reu can handle up to 2 mb ram.
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Post by mirkosoft on Sept 26, 2014 4:14:46 GMT
Truth is that 1700 and 1750 expands C128 memory - total 256 or 640K. Else one variant exist (pre-made for C64 for users reqsts) 1764 upgrade of 256K RAM. I own modified 1764 with extended memory 1536K (1,5MB). In Basic is possibel to access up to 1MB and in assembler up to 16MB. Look at my web: commodore128.mirkosoft.sk/reu.htmlAlso - own you not modified REU 1750? I want to exchange unmodified 1750 to my modified 1764. Reason: I own SCPU128 with 16MB RAM, so capacity is not so important. For me is important free EPROM socket in 1750. My modified 1765 1,5MB works correctly, no problem. Please let me know if you want to exchange. Miro
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Post by nonefornow on Sept 26, 2014 16:48:15 GMT
Hi Miro,
Sorry but I do not have a C1750 to trade.
I was just trying to understand the reasons as to why C= would limit the C128 expansion to 512K when in reality it looks as if the C128 can handle more RAM.
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Post by mirkosoft on Sept 27, 2014 16:12:59 GMT
REU has limit of 256 banks - it looks like indirect 24-bit addressing. But this is external, no indirect - look at my web, there is written how to do it. In reality SuperCPU has 24-bit indirect addressing - no extra operation, standard R/W... And SuperCPU has the same limit 256 banks. Before real work with SuperCPU I meant that it's true 24-bit addressing and wanted to enlarge RAM to indirect 32-bit addressing (true 24-bit + 256 banks). 32-bit addressing if it would be possible, really is not, could access 4 GB RAM. So, when you look finally at up to 16 MB. This allows 1541Ultimate - but warning - 1541U-II is not fully compatible with C128. I was owner of both 1 then 2, but later sad that I sold version 1 (compatible + nic)...
Miro
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Post by motrucker on Sept 28, 2014 4:40:37 GMT
@ mirkosoft I think I still have a 1764 that is 512Kb but no other mods. I believe it has a place for a ROM, but no socket yet. Would that help you?
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Post by hydrophilic on Sept 28, 2014 7:48:27 GMT
512K is just marketing hype... Commodore had/was developing the 512k RAM expander (model 1750) which was the largest available at the time.
Like Mirkosoft said, you can hack the 17xx series REUs to supply up to 2MB.
The 'REU Proctocol' (i.e., how the registers in the $df00 region are programmed) in theory will allow 16MB. This is not possible with an 'official' CBM REU (17xx), but has been made a reality with devices like 1541 Ultimate... (however there is a bug/feature when crossing 2MB boundaries).
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Post by motrucker on Sept 29, 2014 21:53:14 GMT
I understand t he REU. I have had 2Mb units in the past. Miro was asking for a 1750 with a ROM socket. Just thought I would ask if the 1764 would work for him. It might be a moot question, because I can't seem to find the darned thing....
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Post by mirkosoft on Sept 30, 2014 17:07:52 GMT
For me is not important REU size, only EPROM socket.
Miro
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Post by donno128 on Oct 6, 2014 13:36:29 GMT
I have the 1764, to use the Eprom socket it would need to have the solder removed. So, a job if one has no real soldering skill or the desire to do it. Those holes look smaller every day. 63 year old eyes.
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